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Trichomoniasis is caused by a sexually transmitted flagellate protozoan parasite Trichomonas vaginalis. T. vaginalis-derived secretory products (TvSP) contain lipid mediators such as leukotriene B4 (LTB4) and various cysteinyl leukotrienes (CysLTs) which included LTC4, LTD4, and LTE4. However, the signaling mechanisms by which T. vaginalis-induced CysLTs stimulate interleukin (IL)-8 production in human mast cells remain unclear. In this study, we investigated these mechanisms in human mast cells (HMC-1). Stimulation with TvSP resulted in increased intracellular reactive oxygen species (ROS) generation and NADPH oxidase 2 (NOX2) activation compared to unstimulated cells. Pre-treatment with NOX2 inhibitors such as diphenyleneiodonium chloride (DPI) or apocynin significantly reduced ROS production in TvSP-stimulated HMC-1 cells. Additionally, TvSP stimulation increased NOX2 protein expression and the translocation of p47phox from the cytosol to the membrane. Pretreatment of HMC-1 cells with PI3K or PKC inhibitors reduced TvSP-induced p47phox translocation and ROS generation. Furthermore, NOX2 inhibitors or NOX2 siRNA prevented CREB phosphorylation and IL-8 gene expression or protein secretion induced by TvSP. Pretreatment with a CysLTR antagonist significantly inhibited TvSP-induced ROS production, CREB phosphorylation, and IL-8 production. These results indicate that CysLT-mediated activation of NOX2 plays a crucial role in ROS-dependent IL-8 production in human mast cells stimulated by T. vaginalis-secreted CysLTs. These findings enhance our understanding of the inflammatory response in trichomoniasis and may inform the development of targeted therapies to mitigate this response.

Background: Mast cells are known to affect the primary and secondary immune responses against parasites, and this effect is partially mediated through the release of pro-angiogenic mediators. The aim of this study was to explore the effect of the mast cell stabilizer (MCS), ketotifen, with and without albendazole, an anti-parasitic prescription medicine, on the inflammatory response against Trichinella spiralis, with the overall aim to investigate its effect on angiogenesis accompanying nurse cell formation., Methods: The effect of ketotifen and albendazole was explored in eight groups of female BALB/c mice. Four groups were sensitized with a small dose of T. spiralis larvae. The drug regimen was then applied to both sensitized (challenged) and non-sensitized mice. The parasite load was assessed by histopathological examination of the small intestine and muscle tissue, and angiogenesis was assessed by immunohistochemistry to determine the expression of vascular endothelial growth factor (VEGF)., Results: Sensitized mice showed a significantly lower parasite load and a more pronounced inflammatory response than mice receiving a single infective dose of T. spiralis larvae. All treated groups showed a significant reduction in parasite count compared to the control groups (groups IAa and IBa), reaching approximately an 98.8% reduction in adult parasite count in the sensitized group treated with albendazole (groups IIAb and IIBb). MCS significantly decreased the parasite count during both the intestinal or muscular phases, reduced tissue inflammation, and decreased local VEGF expression, both in the non-sensitized and sensitized groups., Conclusion: Sensitization with a low dose of T. spiralis larvae was found to confer a partial protective immunity against re-infection and to positively affect the study outcomes, thus underlining the importance of vaccination, but after extensive studies. The anti-angiogenic effect of MCS protects against larval encystation during the muscle phase. The anti-angiogenic potential of albendazole suggests that the action of this anti-helminthic during trichinellosis is not confined to structural damage to the parasite cuticle but includes an effect on host immunopathological response., (© 2021. The Author(s).)

Pathogen interactions arising during coinfection can exacerbate disease severity, for example when the immune response mounted against one pathogen negatively affects defense of another. It is also possible that host immune responses to a pathogen, shaped by historical evolutionary interactions between host and pathogen, may modify host immune defenses in ways that have repercussions for other pathogens. In this case, negative interactions between two pathogens could emerge even in the absence of concurrent infection. Parasitic worms and tuberculosis (TB) are involved in one of the most geographically extensive of pathogen interactions, and during coinfection worms can exacerbate TB disease outcomes. Here, we show that in a wild mammal natural resistance to worms affects bovine tuberculosis (BTB) severity independently of active worm infection. We found that worm-resistant individuals were more likely to die of BTB than were nonresistant individuals, and their disease progressed more quickly. Anthelmintic treatment moderated, but did not eliminate, the resistance effect, and the effects of resistance and treatment were opposite and additive, with untreated, resistant individuals experiencing the highest mortality. Furthermore, resistance and anthelmintic treatment had nonoverlapping effects on BTB pathology. The effects of resistance manifested in the lungs (the primary site of BTB infection), while the effects of treatment manifested almost entirely in the lymph nodes (the site of disseminated disease), suggesting that resistance and active worm infection affect BTB progression via distinct mechanisms. Our findings reveal that interactions between pathogens can occur as a consequence of processes arising on very different timescales., Competing Interests: The authors declare no competing interest.

Defence mechanisms of fish can be divided into specific and non-specific that act in concert and are often interdependent. Most fish in both wild and cultured populations are vulnerable to metazoan parasites. Endoparasitic helminths include several species of digeneans, cestodes, nematodes, and acanthocephalans. Although they may occur in large numbers, helminth infections rarely result in fish mortality. Conversely, some ectoparasites cause mass mortality in farmed fish. Given the importance of fish innate immunity, this review addresses non-specific defence mechanisms of fish against metazoan parasites, with emphasis on granulocyte responses involving mast cells, neutrophils, macrophages, rodlet cells, and mucous cells. Metazoan parasites are important disease agents that affect wild and farmed fish and can induce high economic loss and, as pathogen organisms, deserve considerable attention. The paper will provide our light and transmission electron microscopy data on metazoan parasites-fish innate immune and neuroendocrine systems. Insights about the structure and functions of the cell types listed above and a brief account of the effects and harms of each metazoan taxon to specific fish apparati/organs will be presented., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Anti-helminth responses require robust type 2 cytokine production that simultaneously promotes worm expulsion and initiates the resolution of helminth-induced wounds and hemorrhaging. However, how infection-induced changes in hematopoiesis contribute to these seemingly distinct processes remains unknown. Recent studies have suggested the existence of a hematopoietic progenitor with dual mast cell-erythrocyte potential. Nonetheless, whether and how these progenitors contribute to host protection during an active infection remains to be defined. Here, we employed single cell RNA-sequencing and identified that the metabolic enzyme, carbonic anhydrase (Car) 1 marks a predefined bone marrow-resident hematopoietic progenitor cell (HPC) population. Next, we generated a Car1-reporter mouse model and found that Car1-GFP positive progenitors represent bipotent mast cell/erythrocyte precursors. Finally, we show that Car1-expressing HPCs simultaneously support mast cell and erythrocyte responses during Trichinella spiralis infection. Collectively, these data suggest that mast cell/erythrocyte precursors are mobilized to promote type 2 cytokine responses and alleviate helminth-induced blood loss, developmentally linking these processes. Collectively, these studies reveal unappreciated hematopoietic events initiated by the host to combat helminth parasites and provide insight into the evolutionary pressure that may have shaped the developmental relationship between mast cells and erythrocytes., Competing Interests: Mark C. Siracusa is the founder and president of NemaGen Discoveries.

Background: Mast cells are involved in the host immune response controlling infection with the non-invasive intestinal protozoan parasite Giardia intestinalis. Experimental infections in rodents with G. intestinalis showed increased intestinal expression of mucosal and connective mast cell specific proteases suggesting that both mucosal and connective tissue mast cells are recruited and activated during infection. During infection Giardia excretory-secretory proteins (ESPs) with immunomodulatory capacity are released. However, studies investigating potential interactions between Giardia ESPs and the connective tissue mast cell specific serine proteases, i.e. human chymase and mouse mast cell protease (mMCP)-4 and, human and mouse tryptase (mMCP-6) remain scarce., Results: We first investigated if soluble Giardia proteins (sGPs), which over-lap extensively in protein content with ESP fractions, from the isolates GS, WB and H3, could induce mast cell activation. sGPs induced a minor activation of bone marrow derived mucosal-like mast cells, as indicated by increased IL-6 secretion and no degranulation. Furthermore, sGPs were highly resistant to degradation by human tryptase while human chymase degraded a 65 kDa sGP and, wild-type mouse ear tissue extracts degraded several protein bands in the 10 to 75 kDa range. In striking contrast, sGPs and ESPs were found to increase the enzymatic activity of human and mouse tryptase and to reduce the activity of human and mouse chymase., Conclusion: Our finding suggests that Giardia ssp. via enhancement or reduction of mast cell protease activity may modulate mast cell-driven intestinal immune responses. ESP-mediated modulation of the mast cell specific proteases may also increase degradation of tight junctions, which may be beneficial for Giardia ssp. during infection., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Objective: To analyze the remodeling dynamics of total collagen, type I and III, the expression of ICAM-1 and 5-HT in the jejunum of rats., Methods: Twenty-eight Wistar rats were randomly assigned to two experimental groups: the control group (CG, n = 7) and the infected group (receiving 5,000 sporulated T. gondii oocysts - ME49 strain, genotype II, n = 21). Seven infected rats each at 6 (G6), 12 (G12), and 24 (G24) hours post infection were sacrificed and segments of jejunum were collected for standard histological, histochemical, and immunohistochemistry processing techniques., Results: The infection promoted ICAM-1 and 5-HT expression, type III collagen, and total mast cell increases. However, it also caused a reduction in the area occupied by type I collagen fibers, and in submucosa thickness, and caused ganglion and peri-ganglion alterations., Conclusion: The structural damage caused by toxoplasmic infection is intense during the first 24 h post inoculation. At peak dissemination, from 12 to 24 h, there is an increase in ICAM-1 and 5-HT expression, with intense migration of mast cells to the site of infection. There was also a reduction in submucosa thickness, and an effective loss of extracellular matrix (ECM) organization, which included changes in the dynamics of type I and III total collagen deposition., (Copyright © 2019 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

Infection with helminth parasites evokes a complex cellular response in the host, where granulocytes (i.e. eosinophils, basophils and mast cells (MCs)) feature prominently. In addition to being used as markers of helminthic infections, MCs have been implicated in worm expulsion since animals defective in c-kit signaling, which results in diminished MC numbers, can have delayed worm expulsion. The role of MCs in the rejection of the rat tapeworm, Hymenolepsis diminuta , from the non-permissive mouse host is not known. MC-deficient mice display a delay in the expulsion of H. diminuta that is accompanied by a less intense splenic Th2 response, as determined by in vitro release of interleukin (IL)-4, IL-5 and IL-13 cytokines. Moreover, worms retrieved from MC-deficient mice were larger than those from wild-type (WT) mice. Assessment of gut-derived IL-25, IL-33, thymic stromal lymphopoietin revealed lower levels in uninfected MC-deficient mice compared with WT, suggesting a role for MCs in homeostatic control of these cytokines: differences in these gut cytokines between the mouse strains were not observed after infection with H. diminuta Finally, mice infected with H. diminuta display less severe dinitrobenzene sulphonic acid (DNBS)-induced colitis, and this beneficial effect of the worm was unaltered in MC-deficient mice challenged with DNBS, as assessed by a macroscopic disease score. Thus, while MCs are not essential for rejection of H. diminuta from mice, their absence slows the kinetics of expulsion allowing the development of greater worm biomass prior to successful rejection of the parasitic burden., (© 2018 The Author(s).)

Trichomonas vaginalis is a sexually-transmitted protozoan parasite that causes vaginitis and cervicitis. Although mast cell activation is important for provoking tissue inflammation during infection with parasites, information regarding the signaling mechanisms in mast cell activation and T. vaginalis infection is limited. O-linked N-acetylglucosamine (O-GlcNAc) is a post-translational modification of serine and threonine residues that functions as a critical regulator of intracellular signaling, regulated by O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA). We investigated if O-GlcNAcylation was associated with mast cell activation induced by T. vaginalis-derived secretory products (TvSP). Modified TvSP collected from live trichomonads treated with the 5-lipooxygenase inhibitor AA861 inhibited migration of mast cells. This result suggested that mast cell migration was caused by stimulation of T. vaginalis-secreted leukotrienes. Using the BLT1 antagonist U75302 or BLT1 siRNA, we found that migration of mast cells was evoked via LTB 4 receptor (BLT1). Furthermore, TvSP induced protein O-GlcNAcylation and OGT expression in HMC-1 cells, which was prevented by transfection with BLT1 siRNA. TvSP-induced migration, ROS generation, CD63 expression and IL-8 release were significantly suppressed by pretreatment with OGT inhibitor ST045849 or OGT siRNA. These results suggested that BLT1-mediated OGlcNAcylation was important for mast cell activation during trichomoniasis., (Copyright © 2018 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.)

Background: Trypanosoma cruzi (T. cruzi) infects millions of Latin Americans each year and can induce chagasic megacolon. Little is known about how serotonin (5-HT) modulates this condition. Aim We investigated whether 5-HT synthesis alters T. cruzi infection in the colon., Materials and Methods: Forty-eight paraffin-embedded samples from normal colon and chagasic megacolon were histopathologically analyzed (173/2009). Tryptophan hydroxylase 1 (Tph1) knockout (KO) mice and c-Kit W-sh mice underwent T. cruzi infection together with their wild-type counterparts. Also, mice underwent different drug treatments (16.1.1064.60.3)., Results: In both humans and experimental mouse models, the serotonergic system was activated by T. cruzi infection (p < 0.05). While treating Tph1KO mice with 5-HT did not significantly increase parasitemia in the colon (p > 0.05), rescuing its synthesis promoted trypanosomiasis (p < 0.01). T. cruzi-related 5-HT release (p < 0.05) seemed not only to increase inflammatory signaling, but also to enlarge the pericryptal macrophage and mast cell populations (p < 0.01). Knocking out mast cells reduced trypanosomiasis (p < 0.01), although it did not further alter the neuroendocrine cell number and Tph1 expression (p > 0.05). Further experimentation revealed that pharmacologically inhibiting mast cell activity reduced colonic infection (p < 0.01). A similar finding was achieved when 5-HT synthesis was blocked in c-Kit W-sh mice (p > 0.05). However, inhibiting mast cell activity in Tph1KO mice increased colonic trypanosomiasis (p < 0.01)., Conclusion: We show that mast cells may modulate the T. cruzi-related increase of 5-HT synthesis in the intestinal colon.

Type-2-cell-mediated immune responses play a critical role in mediating both host-resistance and disease-tolerance mechanisms during helminth infections. Recently, type 2 cell responses have emerged as major regulators of tissue repair and metabolic homeostasis even under steady-state conditions. In this review, we consider how studies of helminth infection have contributed toward our expanding cellular and molecular understanding of type-2-cell-mediated immunity, as well as new areas such as the microbiome. By studying how these successful parasites form chronic infections without overt pathology, we are gaining additional insights into allergic and inflammatory diseases, as well as normal physiology., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Immunohistochemical, immunofluorescence and ultrastructural studies were conducted on a sub-population of 20 wels catfish Silurus glanis from a tributary of the River Po (Northern Italy). Fish were examined for the presence of ecto- and endo-parasites; in the intestine of 5 fish, 11 specimens of cestode Glanitaenia osculata were noted and was the only helminth species encountered. The architecture of intestine and its cellular features were nearly identical in either the uninfected S. glanis or in those harboring G. osculata. Near the site of worm's attachment, mucous cells, several mast cells (MCs), few neutrophils and some endocrine cells (ECs) were found to co-occur within the intestinal epithelium. MCs and neutrophils were abundant also in the submucosa. Immunohistochemical staining revealed that enteric ECs were immunoreactive to met-enkephalin, galanin and serotonin anti-bodies. The numbers of ECs, mucous cells and MCs were significantly higher in infected wels catfish (Mann-Whitney U test, p < 0.05). Dual immunofluorescence staining with the biotinylated lectin Sambucus nigra Agglutinin and the rabbit polyclonal anti-met-enkephalin or anti-serotonin, with parallel transmission electron microscopy, showed that ECs often made intimate contact with the mucous cells and epithelial MCs. The presence of numerous MCs in intestinal epithelium shows S. glanis to be an interesting model fish to study processes underlying intestinal inflammation elicited by an enteric worm. Immune cells, ECs and mucous cells of the intestinal epithelium have been described at the ultrastructural level and their possible functions and interactions together will be discussed., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Mast cells and basophils are innate immune cells with overlapping functions that contribute to anti-helminth immunity. Mast cell function during helminth infection was previously studied using mast cell-deficient Kit-mutant mice that display additional mast cell-unrelated immune deficiencies. Here, we use mice that lack basophils or mucosal and connective tissue mast cells in a Kit-independent manner to re-evaluate the impact of each cell type during helminth infection. Neither mast cells nor basophils participated in the immune response to tissue-migrating Strongyloides ratti third-stage larvae, but both cell types contributed to the early expulsion of parasitic adults from the intestine. The termination of S. ratti infection required the presence of mucosal mast cells: Cpa3 Cre mice, which lack mucosal and connective tissue mast cells, remained infected for more than 150 days. Mcpt5 Cre R-DTA mice, which lack connective tissue mast cells only, and basophil-deficient Mcpt8 Cre mice terminated the infection after 1 month with wild-type kinetics despite their initial increase in intestinal parasite burden. Because Cpa3 Cre mice showed intact Th2 polarization and efficiently developed protective immunity after vaccination, we hypothesize that mucosal mast cells are non-redundant terminal effector cells in the intestinal epithelium that execute anti-helminth immunity but do not orchestrate it.

Background: Serglycin proteoglycans are essential for maturation of secretory granules and for the correct granular storage of cationic proteases in hematopoietic cells, e.g. mast cells. However, little is known about the in vivo functions of serglycin proteoglycans during infection. Here we investigated the potential role of serglycin proteoglycans in host defense after infection with the nematode Trichinella spiralis., Results: Twelve days post infection lack of serglycin proteoglycans caused significantly increased enteropathy. The serglycin-deficient mice showed significantly increased intestinal worm burden, reduced recruitment of mast cells to the intestinal crypts, decreased levels of the mast cell proteases MCPT5 and MCPT6 in intestinal tissue, decreased serum levels of TNF-α, IL-1β, IL-10 and IL-13, increased levels of IL-4 and total IgE in serum, and increased intestinal levels of the neutrophil markers myeloperoxidase and elastase, as compared to wild type mice. At five weeks post infection, increased larvae burden and inflammation were seen in the muscle tissue of the serglycin-deficient mice., Conclusions: Our results demonstrate that the serglycin-deficient mice were more susceptible to T. spiralis infection and displayed an unbalanced immune response compared to wild type mice. These findings point to an essential regulatory role of serglycin proteoglycans in immunity.

A sub-population of 34 specimens of chub, Squalius cephalus, was sampled from the River Brenta (Northern Italy) and examined for ecto- and endo-parasites. Pomphorhynchus laevis (Acanthocephala) was the only enteric helminth encountered. Immunofluorescence and ultrastructural studies were conducted on the intestines of chub. Near the site of parasite's attachment, mucous cells, mast cells (MCs), neutrophils and rodlet cells (RCs) were found to co-occur within the intestinal epithelium. The numbers of mucous cells, MCs and neutrophils were significantly higher in infected fish (Mann-Whitney U test, p < 0.05). Dual immunofluorescence staining with the lectin Dolichos Biflorus Agglutinin (DBA) and the macrophage-specific MAC387 monoclonal antibody, with parallel transmission electron microscopy, revealed that epithelial MCs often made intimate contact with the mucous cells. Degranulation of a large number of MCs around the site of the acanthocephalan's attachment and in proximity to mucous cells was also documented. MCs and neutrophils were abundant in the submucosa. Immune cells of the intestinal epithelium have been described at the ultrastructural level and their possible functions and interactions are discussed., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Aim: To compare the efficacy ofprednisolone, montelukast, and omalizumab in reducing allergic symptoms and inflammation at tissue level in an experimental allergic rhinitis model., Materials and Methods: Forty Sprague Dawley rats were randomized into 5 groups as naive (NS/NC), sensitized/challenged (S/C) by subcutaneous ovalbumin antigen injection, and montelukast-, prednisolone-, and omalizumab-treated groups. A nasal allergen challenge was performed every day from day 20 to day 26. The number of sneezes and nasal/eye rubbing movements, IL-4 and CysLT levels in serum, nasal and bronchoalveolar lavage fluids determined by ELISA, and histopathological findings of nasal mucosa, sinus, and lung tissues were compared., Results: All of the treatments significantly controlled the allergic symptoms of sneezing and nasal/eye rubbing (P < 0.05). IL-4 and CysLT levels on days 20 and 26 were significantly higher in the S/C group compared to the NS/NC group (P < 0.05). Montelukast significantly decreased serum and nasal IL-4 and CysLT levels (P < 0.05), prednisolone decreased nasal lavage IL-4 and CysLT levels (P < 0.05), and omalizumab lowered nasal lavage CysLT levels (P < 0.05)., Conclusion: Prednisolone, montelukast, and omalizumab were found to be effective in controlling the allergic symptoms of allergic rhinitis and upper/lower airway inflammation in an experimental allergic rhinitis model.

Once animals have experienced a helminthic infection, they often show stronger protective immunity against subsequent infections. Although helminthic infections are well known to elicit Th2-type immune responses, it remains ill-defined where and how acquired protection is executed. Here we show that skin-invading larvae of the intestinal helminth Nippostrongylus brasiliensis are surrounded by skin-infiltrating cells and are prevented from migrating out of infected skin during the second but not the first infection. B cell- or IgE receptor FcεRI-deficient mice showed impaired larval trapping in the skin. Selective ablation of basophils, but not mast cells, abolished the larval trapping, leading to increased worm burden in the lung and hence severe lung injury. Skin-infiltrating basophils produced IL-4 that in turn promoted the generation of M2-type macrophages, leading to the larval trapping in the skin through arginase-1 production. Basophils had no apparent contribution to worm expulsion from the intestine. This study thus reveals a novel mode of acquired antihelminth immunity, in which IgE-armed basophils mediate skin trapping of larvae, thereby limiting lung injury caused by larval migration.

The host deploys a subset of immune responses to expel helminths, which differs depending on the nature of the helminth. Strongyloides venezuelensis, a counterpart of the human pathogen S. stercoralis, naturally infects rodents and has been used as an experimental model. Here we show that induction of immunoglobulin G (IgG) and IgE is a prerequisite for rapid expulsion of S. venezuelensis during a primary infection. Activation-induced cytidine deaminase-deficient (AID(-/-)) mice, which lack the ability to switch IgM to other isotypes, normally developed T-helper 2 (Th2) cells and intestinal mastocytosis after infection with S. venezuelensis. Although AID(-/-) mice expelled Nippostrongylus brasiliensis normally, they required a much longer period to expel S. venezuelensis than wild-type (WT) mice. Adoptive transfers of immune sera from S. venezuelensis-infected but not N. brasiliensis-infected mice restored the ability of AID(-/-) mice to promptly expel S. venezuelensis. Immune serum-derived IgG and IgE induced worm expulsion via Fc γ receptor III (FcγRIII) and Fc ε receptor I (FcεRI), respectively, and a mixture of IgG and IgE showed collaborative effects. Whereas FcγRIII(-/-) mice or FcεRIα(-/-) mice normally could expel S. venezuelensis, FcγRIII(-/-) mice, when their IgE was neutralized by anti-IgE, or FcεRIα(-/-) mice, when their IgG binding to FcγRIII was blocked by anti-FcγRIII, showed a markedly reduced ability to expel S. venezuelensis. These data reveal that IgG and IgE play redundant roles but act in concert to accelerate S. venezuelensis expulsion. Mast cell-deficient mice, even those equipped with immune serum-derived IgG or IgE, failed to expel S. venezuelensis promptly, suggesting that mast cells are cellular targets of IgG and IgE.

Mast cells (MC) and basophils share expression of the high-affinity receptor for IgE (FcεRI) but can be distinguished by their divergent expression of KIT and CD49b. In BALB/c mice, MC lineage cells expressing high levels of FcεRI by flow cytometry were seen only in bone marrow whereas those expressing intermediate levels of FcεRI were present in bone marrow and spleen of naive mice and in mesenteric lymph nodes (mLN) of Trichinella spiralis-infected mice. These FcεRI(+)KIT(+)CD49b(-) cells had a membrane phenotype similar to i.p. connective tissue-type MC, but were smaller and hypogranular by flow cytometry forward and side scatter profiles, respectively. Consistent with this, they lacked the prominent secretory granules identified by histochemistry and immunodetection for the MC-specific granule proteases that are readily seen in mature jejunal mucosal MC that also are induced by the infection and present at the same time. The concentration of these MC lineage cells in mLN determined by flow cytometry was comparable to that of MC progenitors (MCp) measured by limiting dilution and clonal expansion with maturation. We observed upregulation of IL-4 transcription by MCp in mLN and spleens of helminth-infected 4get mice, and we demonstrated by intracellular cytokine staining production of IL-4 and IL-6 by the mLN MCp in helminth-infected mice. Furthermore, treatment of helminth-infected mice with anti-FcεRI mAb, a protocol known to deplete basophils, also depleted mLN MCp. Thus, this study identifies a hypogranular subset of MCp recruited to mLN by helminth infection that may be an important unrecognized source of cytokines.

Myeloid-derived suppressor cells (MDSCs) are primarily recognized for their immunosuppressive properties in malignant disease. However, their interaction with other innate immune cells and their regulation of immune responses, such as in parasitic infection, necessitate further characterization. We used our previously published mouse model of MDSC accumulation to examine the immunoregulatory role of MDSCs in B16 melanoma metastasis and Nippostrongylus brasiliensis infection. In this study, we demonstrate that the activity of MDSCs is dependent on the immune stimuli and subset induced. Monocytic MDSCs predictably suppressed antitumor immune responses but granulocytic MDSCs surprisingly enhanced the clearance of N. brasiliensis infection. Intriguingly, both results were dependent on MDSC interaction with mast cells (MCs), as demonstrated by adoptive-transfer studies in MC-deficient (Kit(Wsh)(/)(Wsh)) mice. These findings were further supported by ex vivo cocultures of MCs and MDSCs, indicating a synergistic increase in cytokine production. Thus, MCs can enhance both immunosuppressive and immunosupportive functions of MDSCs.

This review describes different aspects of the host immune response to Trichinella. The role of antibodies, T cells, mast cells, eosinophils and neutrophils in immune reaction to this nematode is considered, in the light of the recent data derived from experimental models, both in in vivo and in vitro. The knowledge of immune response mechanisms against Trichinella is fundamental to understand how the parasite can escape such mechanisms. The principal evasion mechanisms of host immune response occurring in trichinellosis are described, some of which are shared by other parasites, some others are peculiar of this parasite, but particular attention is focused on immunomodulation and the possibilities to exploit this parasite ability to verify the effects on immuno-mediated diseases. In conclusion, some considerations on the actual ability to escape the host immune response by the parasite are discussed, taking into account the recent data that shows that the parasite might rather drive immune system of the host towards a less dangerous response.

Mast cells (MCs) deficient rats (Ws/Ws) were used to investigate the roles of MCs in visceral hyperalgesia. Ws/Ws and wild control (+/+) rats were exposed to T. spiralis or submitted to acute cold restraint stress (ACRS). Levels of proteinase-activated receptor 2 (PAR2) and nerve growth factor (NGF) were determined by immunoblots and RT-PCR analysis, and the putative signal pathways including phosphorylated extracellular-regulated kinase (pERK1/2) and transient receptor potential vanilloid receptor 1 (TRPV1) were further identified. Visceral hyperalgesia triggered by ACRS was observed only in +/+ rats. The increased expression of PAR2 and NGF was observed only in +/+ rats induced by T. spiralis and ACRS. The activation of pERK1/2 induced by ACRS occurred only in +/+ rats. However, a significant increase of TRPV1 induced by T. spiralis and ACRS was observed only in +/+ rats. The activation of PAR2 and NGF via both TRPV1 and pERK1/2 signal pathway is dependent on MCs in ACRS-induced visceral hyperalgesia rats.

Although the roles of mast cells (MCs) are essential in many inflammatory and fibrotic diseases, their role in Trypanosoma cruzi-induced cardiomyopathy is unexplored. In this study, we treated infected CBA mice with cromolyn, an MC stabilizer, and observed much greater parasitemia and interferon-γ levels, higher mortality, myocarditis, and cardiac damage. Although these data show that MCs are important in controlling acute infection, we observed MC apoptosis in the cardiac tissue and peritoneal cavity of untreated mice. In the heart, pericardial mucosal MC die, perhaps because of reduced amounts of local stem cell factor. Using RT-PCR in purified cardiac MCs, we observed that infection induced transcription of P2X(7) receptor and Fas, two molecules reportedly involved in cell death and inflammatory regulation. In gld/gld mice (FasL(-/-)), apoptosis of cardiac, but not peritoneal, MCs was decreased. Conversely, infection of P2X(7)(-/-) mice led to reduced peritoneal, but not cardiac, MC death. These data illustrate the immunomodulatory role played by MCs in T. cruzi infection and the complexity of molecular interactions that control inflammatory pathways in different tissues and compartments., (Copyright © 2011 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

Smooth muscle cells can produce stem cell factor (SCF) in the normal state for the preservation of mast cells, but it is still unknown whether smooth muscle cells can enhance SCF production in response to the pathological stimuli. The present study showed that smooth muscle cells in mast cell-increased regions around worm cysts of intestinal nematodes significantly enhanced SCF gene expression compared with mast cell non-increased regions in same sample. SCF gene expression in mast cell non-increased regions in nematode-infected mice showed almost the same level as in non-infected control groups. These results indicate that smooth muscle cells can locally enhance SCF gene expression, and may have a role in local immunological reactions as growth factor-producing cells.

It is well known that eosinophilia is a key pathogenetic component of toxocariasis. The objective of the present study was to determine if there is an association between peritoneal and blood eosinophil influx, mast cell hyperplasia and leukotriene B(4) (LTB(4)) production after Toxocara canis infection. Oral inoculation of 56-day-old Wistar rats (N = 5-7 per group) with 1000 embryonated eggs containing third-stage (L3) T. canis larvae led to a robust accumulation of total leukocytes in blood beginning on day 3 and peaking on day 18, mainly characterized by eosinophils and accompanied by higher serum LTB(4) levels. At that time, we also noted increased eosinophil numbers in the peritoneal cavity. In addition, we observed increased peritoneal mast cell number in the peritoneal cavity, which correlated with the time course of eosinophilia during toxocariasis. We also demonstrated that mast cell hyperplasia in the intestines and lungs began soon after the T. canis larvae migrated to these compartments, reaching maximal levels on day 24, which correlated with the complete elimination of the parasite. Therefore, mast cells appear to be involved in peritoneal and blood eosinophil infiltration through an LTB(4)-dependent mechanism following T. canis infection in rats. Our data also demonstrate a tight association between larval migratory stages and intestinal and pulmonary mast cell hyperplasia in the toxocariasis model.

Suffolk sheep carrying the DRB1*1101 (previously referred to as-DRB1*0203 or G2) allele have been reported to show increased resistance to natural Teladorsagia circumcincta infection compared to non-carriers. The objective of this study was to compare the biochemical and physiological responses of DRB1*1101 carrier and non-carrier twin lambs to an experimental infection with 3 × 10(4) L3 Teladorsagia circumcincta. The variables studied included worm burden, faecal egg count, abomasal mast cells, IgA, IgE, IgG1 plus IgG2 and haematological parameters at 0, 3, 7, 21 and 35 days post infection (dpi), and duodenal smooth muscle contractility at 0 and 35 dpi. DRB1*1101 carrier lambs had significantly lower worm burden, higher mast cell and plasma platelet counts than the DRB1*1101 non-carriers (P < 0.05). Before infection, the non-carrier lambs exhibited significantly higher mucosal levels of all antibody isotypes measured compared to the carriers; these levels remained relatively stable over the course of infection in the non-carriers while there was a slow build up of these antibodies in the carriers up to day 21 post infection (pi). The DRB1*1101 non-carrier lambs had a significantly higher plasma lymphocyte count, and produced greater duodenal contractile force relative to the carrier lambs (P < 0.05). There was no significant difference between genotypes in the level of plasma eosinophils, monocytes, neutrophils or FEC. This evidence suggests that resistance conferred by DRB1*1101 is acquired rather than innate, depends on worm expulsion rather than fecundity and is dependent on mucosal mast cell proliferation, platelet activation, and IgA and IgE antibody responses.

Mast cells have been reported to be predominant in the vaginal smears of patients infected with T. vaginalis. In this study, we investigated whether T. vaginalis could induce mast cells to migrate and to produce TNF-alpha and histamine. Rat peritoneal mast cells (RPMC), a primary mast cell, were used for the study. T. vaginalis induced an increase in chemotactic migration of the mast cells toward excretory and secretory product (ESP) of T. vaginalis, and the mast cells activated with T. vaginalis showed an increased release of histamine and TNF-alpha. Therefore, mast cells may be involved in the inflammatory response caused by T. vaginalis.

Notch receptor-mediated signaling is involved in the developmental process and functional modulation of lymphocytes, as well as in mast cell differentiation. Here, we investigated whether Notch signaling is required for antipathogen host defense regulated by mast cells. Mast cells were rarely found in the small intestine of wild-type C57BL/6 mice but accumulated abnormally in the lamina propria of the small-intestinal mucosa of the Notch2-conditional knockout mice in naive status. When transplanted into mast cell-deficient W(sh)/W(sh) mice, Notch2-null bone marrow-derived mast cells were rarely found within the epithelial layer but abnormally localized to the lamina propria, whereas control bone marrow-derived mast cells were mainly found within the epithelial layer. After the infection of Notch2 knockout and control mice with L3 larvae of Strongyloides venezuelensis, the abundant number of mast cells was rapidly mobilized to the epithelial layer in the control mice. In contrast, mast cells were massively accumulated in the lamina propria of the small intestinal mucosa in Notch2-conditional knockout mice, accompanied by impaired eradication of Strongyloides venezuelensis. These findings indicate that cell-autonomous Notch2 signaling in mast cells is required for proper localization of intestinal mast cells and further imply a critical role of Notch signaling in the host-pathogen interface in the small intestine.

Mammals are serially infected with a variety of microorganisms, including bacteria and parasites. Each infection reprograms the immune system's responses to re-exposure and potentially alters responses to first-time infection by different microorganisms. To examine whether infection with a metazoan parasite modulates host responses to subsequent bacterial infection, mice were infected with the hookworm-like intestinal nematode Nippostrongylus brasiliensis, followed in 2-4 weeks by peritoneal injection of the pathogenic bacterium Klebsiella pneumoniae. Survival from Klebsiella peritonitis two weeks after parasite infection was better in Nippostrongylus-infected animals than in unparasitized mice, with Nippostrongylus-infected mice having fewer peritoneal bacteria, more neutrophils, and higher levels of protective interleukin 6. The improved survival of Nippostrongylus-infected mice depends on IL-4 because the survival benefit is lost in mice lacking IL-4. Because mast cells protect mice from Klebsiella peritonitis, we examined responses in mast cell-deficient Kit(W-sh)/Kit(W-sh) mice, in which parasitosis failed to improve survival from Klebsiella peritonitis. However, adoptive transfer of cultured mast cells to Kit(W-sh)/Kit(W-sh) mice restored survival benefits of parasitosis. These results show that recent infection with Nippostrongylus brasiliensis protects mice from Klebsiella peritonitis by modulating mast cell contributions to host defense, and suggest more generally that parasitosis can yield survival advantages to a bacterially infected host.

Giardia lamblia is a common cause of both acute and chronic diarrheal disease in humans worldwide. It has been shown that mast cells, IL-6 and TNF-alpha are substantially involved in the early control of G. lamblia infection in mice. However, no studies have yet been reported concerning the interaction between mast cell and Giardia, as well as the mast cells mediators generated in response to Giardia infection. In this study we demonstrated the direct activation of mast cells by G. lamblia live trophozoites or trophozoite-derived antigens followed by an increase in tryptase expression and a significant release of the preformed mediator histamine. In addition, parasite derived antigens increased TNF-alpha and de novo synthesized cytokine IL-6, at the mRNA and protein level. These results strongly suggest that mast cells might be an important source not only of IL-6 but also of TNF-alpha during Giardia infection, playing an important role in the outcome of the infection., ((c) 2010 Elsevier Inc. All rights reserved.)

Annual losses of approximately 5-10% of the juvenile stock of European seabass, Dicentrarchus labrax (L.) in the northern coast of the Adriatic Sea has been attributed to heavy infections of the gill monogenean Diplectanum aequans. Immunocytochemical, light and ultrastructural studies were carried out on seabass naturally parasitized with this monogenean. The site of the worm's attachment was marked by the common presence of haemorrhages and white mucoid exudate. In histological sections, infected gills showed hyperplasia, as well as proliferation of mucous cells and rodlet cells. Disruption and fusion of the secondary lamellae were common in all infected seabass, with several specimens also showing marked inflammation and erosion of the primary and secondary lamellar epithelium. Immunostaining of primary and secondary gill filaments with an antibody against the antimicrobial peptide piscidin 3 (anti-piscidin 3 antibody, anti-HAGR) revealed a subpopulation of mast cells that were positive. Mast cells were both within and outside the blood vessels of the primary and secondary lamellae, and often made intimate contact with vascular endothelial cells. Mast cells were irregular in shape with a cytoplasm filled by numerous electron-dense, membrane-bound granules. Our data provide evidence showing the presence of piscidin 3 in the cytoplasmic granules of an important group of fish inflammatory cells, the mast cells resident in seabass gill tissue. There was no significant difference in the number of HAGR-positive mast cells between infected and uninfected fish (ANOVA, p > 0.05). However, mast cells in parasitized gills usually showed much stronger immunostaining intensity compared to those in unparasitized gills. These data are the first to document a response of piscidins or any other antimicrobial peptide of fish to parasite infection and suggest that mast cells may play a role in certain inflammatory responses without a detectable increase in their numbers., (Copyright 2009 Elsevier Ltd. All rights reserved.)

We assessed the mucosal response of previously infected hamsters to low-dose challenge with the hookworm, Ancylostoma ceylanicum. Hamsters were assigned to five treatment groups (Groups 1-5, respectively): naïve, controls; uninterrupted primary infection from day 0; infected, but treated with anthelmintic on day 35 p.i.; challenge control group given only the second infection on day 63; infected initially, cleared of worms and then challenged. Animals were culled on days 73 and 94 (10 and 31 days after challenge), but additional animals were culled from Group 5 on days 80 and 87. The results showed that villus height declined markedly and progressively over time after challenge in Group 5, whilst depth of the Crypts of Lieberkühn and number of mitotic figures in the crypts increased. Mucosal mast cell numbers were only marginally higher than those in naïve controls and not as high as those in mice with uninterrupted infections. Goblet cell counts showed a major increase, as did eosinophils in relation to naïve controls. Paneth cells were also elevated, but did not change over the course of the experiment. The results also drew attention to the tremendous resilience of hookworms, some adult worms surviving throughout, despite highly inflamed intestines.

In order to examine whether FcepsilonRI-dependent degranulation of intestinal mast cells is required for expulsion of intestinal nematode Strongyloides ratti, CD45 exon6-deficient (CD45-/-) mice were inoculated with S. ratti. In CD45-/- mice, egg excretion in feces persisted for more than 30 days following S. ratti larvae inoculation, whereas in wild-type (CD45+/+) mice, the eggs completely disappeared by day 20 post-infection. The number of intestinal mucosal mast cells, which are known effector cells for the expulsion of S. ratti, was 75% lower in CD45-/- mice compared with that in CD45+/+ mice. Adoptive transfer of wild-type T cells from CD45+/+ mice into CD45-/- mice reduced the duration of S. ratti infection to comparable levels observed in CD45+/+ mice, with concomitant increases in intestinal mucosal mast cells. These results showed that CD45 is not involved in the effector function of intestinal mucosal mast cells against S. ratti infection. Since FcepsilonRI-dependent degranulation of mast cells is completely impaired in these CD45 knockout mice, we conclude that FcepsilonRI-dependent degranulation is not required in the protective function of intestinal mucosal mast cells against primary infection of S. ratti.

The course of intestinal inflammatory responses is tightly coordinated by the extensive communication between the immune system and the enteric nervous system, among which the bidirectional mast cell-neuron interaction within the intestinal wall plays a prominent role. Recent research suggests that somatostatin (SOM) is able to inhibit this self-reinforcing network by simultaneously suppressing the inflammatory activities of both neurons and mast cells. Therefore, we assessed the modulatory effects of SOM on both the short-term and long-term effects induced by the main mast cell mediators histamine (HIS) and 5-HT on spinal sensory neurons. Short-term incubation of dorsal root ganglion cultures with HIS and 5-HT induced neuronal CGRP-release and calcium-mediated activation of both neurons and nonneuronal cells, both of which effects were significantly reduced by SOM. In addition, SOM was also able to suppress the increased neuronal expression of pro- and anti-inflammatory peptides induced by long-term exposure to HIS and 5-HT. Immunocytochemical and molecular-biological experiments revealed the possible involvement of somatostatin receptor 1 (SSTR1) and SSTR2A in these profound SOM-dependent effects. These data, combined with the increased expression of pro- and anti-inflammatory peptides and several SSTRs in murine dorsal root ganglia following intestinal inflammation, reveal that intestinal inflammation not only induces the onset of proinflammatory cascades but simultaneously triggers endogenous systems destined to prevent excessive tissue damage. Moreover, these data provide for the first time functional evidence that SOM is able to directly modulate intestinal inflammatory responses by interference with the coordinating mast cell-neuron communication.

Intestinal lymphoid tissues and Peyer's patches (PP) are innervated sites of immune surveillance in the gastrointestinal tract. Following infection with F. hepatica, neuronal hyperplasia and significantly increased eosinophil and mast cell trafficking to colonic PP sites were evident in rat tissues. Nerve-eosinophil associations were significantly elevated in infected colon and colonic PP, as were colonic tissue levels of the circulatory recruitment factors IL-5 and eotaxin. Increased immunoreactivity for neuronal plasticity markers GAP-43 and neural cell adhesion molecule (NCAM) was also found in infected tissues. Such neuronal alterations in the PP during enteric parasitism may have functional consequences on particular or pathogen uptake.

SUMMARYGastrointestinal infection with the nematode Trichinella spiralis is accompanied by a rapid and reversible expansion of the mucosal mast cell and goblet cell populations in the intestinal epithelium, which is associated with the release of their mediators into the gut lumen. Both goblet cell and mast cell hyperplasia are highly dependent on mucosal T-cells and augmented by the cytokines IL-4 and IL-13. However, the contribution of both mast and goblet cells, and the mediators they produce, to the expulsion of the adults of T. spiralis is only beginning to be elucidated through studies predominantly employing T. spiralis-mouse models. In the present article, we review the factors proposed to control T. spiralis-induced mucosal mast cell (MMC) and goblet cell differentiation in the small intestine, and focus on some key MMC and goblet cell effector molecules which may contribute to the expulsion of adult worms and/or inhibition of larval development.

The observation on different hosts infected with Trichinella spiralis that recognized similar muscle larvae (ML) antigens and the fact that different monoclonal antibodies (mAb) had a similar reactivity to ML components prompted a proposal to define a useful classification system for these antigens. For this purpose, an international workshop provided a platform for the classification of T. spiralis antigens. ML antigens were classified in eight groups -- Trichinella spiralis larvae groups, TSL-1 to TSL-8. TSL-1 antigens are highly immunogenic and a number of important studies have been performed to analyse the role of these antigens in the host-parasite interplay. In this context, we have focused on the analysis of the role of TSL-1 antigens in the induction of innate immune responses with particular emphasis on the activation of mast cells (MC) by an IgE-independent pathway. These studies provided evidence on the role of mediator release from TSL-1-activated MC in the development of Type 2 immune responses. The protective role of TSL-1 in T. spiralis-infected mice has been described. In addition, it has been demonstrated that the use of TSL-1 antigens allows for a more sensitive and specific diagnosis of human and animal trichinellosis.

Atopic allergy is characterized by an increase in IgE antibodies that signal through the high-affinity Fcepsilon receptor (FcepsilonRI) to induce the release of inflammatory mediators from mast cells. For unknown reasons, the prevalence of allergic diseases has recently increased steeply in the developed world. However, this increase has not been mirrored in developing countries, even though IgE concentrations are often greatly elevated in individuals from these countries, owing to nonspecific IgE induction by universally present parasitic worms. Here we offer one explanation for this paradox based on the properties of ES-62, a molecule secreted by filarial nematodes. We found that highly purified, endotoxin-free ES-62 directly inhibits the FcepsilonRI-induced release of allergy mediators from human mast cells by selectively blocking key signal transduction events, including phospholipase D-coupled, sphingosine kinase-mediated calcium mobilization and nuclear factor-kappaB activation. ES-62 mediates these effects by forming a complex with Toll-like receptor 4, which results in the sequestration of protein kinase C-alpha (PKC-alpha). This causes caveolae/lipid raft-mediated, proteasome-independent degradation of PKC-alpha, a molecule important for the coupling of FcepsilonRI to phospholipase D and mast cell activation. We also show that ES-62 is able to protect mice from mast cell-dependent hypersensitivity in the skin and lungs, indicating that it has potential as a novel therapeutic for allergy.

Giardia intestinalis is a significant cause of diarrheal disease worldwide. Infections in animal models have been shown to cause changes in gastrointestinal transit that depend on adaptive immune responses and are mediated, in part, through neuronal nitric oxide synthase. Nitric oxide is an inhibitory neurotransmitter, and we therefore investigated potential excitatory pathways that might be involved in the response to Giardia infection. Infected mice exhibited increased spontaneous and cholecystokinin (CCK)-induced contractions of longitudinal smooth muscle. In contrast, enhanced contractile responses were not observed in response to acetylcholine, 5-hydroxytryptamine, or the protease-activated receptor-1 agonist peptide TFFLR. Giardia-induced changes in smooth muscle function appear to be mediated primarily by mast cells, as both spontaneous and CCK-induced contractions were blocked by pretreatment with either ketotifen or compound 48/80. Together, these data support a model in which CCK release triggers mast cell degranulation, leading to increases in smooth muscle contractility. These contractions, coupled with nitric oxide-mediated muscle relaxation, promote intestinal transit and parasite elimination.

Despite our knowledge of somatostatin (SOM) in gastrointestinal functions, little information is available on the SOM receptors (SSTRs) mediating these effects. This study focussed on the expression of SSTRs in non-inflamed and Schistosoma mansoni-infected murine ileum using immunocytochemistry, reverse transcriptase (RT)-PCR and quantitative real time RT-PCR (qPCR). In the non-inflamed ileum, SSTRs showed a widespread, cell-type specific expression pattern. For instance, SSTR2A immunoreactivity was detected in a minor population of submucous but not myenteric glial cells. In the inflamed ileum, significant changes in the expression pattern of SSTRs occurred, with SSTR1 and SSTR3 expression on mucosal mast cells (MMCs) and mucosal nerve fibres. SSTR4-immunoreactive nerve fibres were detected in granulomas and the lamina propria. qPCR experiments indicated significantly increased mRNA levels for SOM, SSTR1 and SSTR3 in inflamed ileum. This study reveals that SSTRs are expressed in specific cell types in murine ileum. Expression of SSTR1 and SSTR3 on MMCs and increased density of SOM-expressing nerve fibres in the lamina propria during inflammation, support the hypothesis that SOM is implicated in the physiological control of MMCs during intestinal inflammation. Evidence is provided that in mouse mainly SSTR1, SSTR3 and SSTR4 are involved in the somatostatinergic inflammatory effects during intestinal schistosomiasis.

Millions of Leishmania major infections in humans are reported worldwide. In experimental infections, various phagocytes predominant in skin--neutrophils, macrophages (MPhi) and dendritic cells (DC)--play very distinct roles for the hosts' immune response against L. major infection and they are sequentially engaged via different pathogen recognition receptors as cutaneous leishmaniasis evolves. In the initial "silent" phase without clinically apparent inflammation, L. major promastigotes are primarily phagocytosed by resident MPhi via CR3. Upon activation of cutaneous mast cells, inflammatory neutrophils and monocytes are recruited to the skin coincident with the development of a nodular plaque. Later on, in established infections, DC-, B cell- and T cell-dependent immunity becomes critically important for lesion resolution. Antibody-mediated uptake of L. major by DC leads to IL-12 production and priming of Th1/Tc1 cells, both of which are required for efficient parasite killing by lesional MPhi. Finally, Fc receptor-mediated uptake of L. major by MPhi induces counter-regulatory IL-10 production leading to parasite persistence. Thus, the balance between CR3- and FcgammaR-triggered anti- and proinflammatory mechanisms involving MPhi and DC is critical for disease outcome. This review highlights the importance of the various phagocytes for the development of anti-Leishmania immunity.

Mast cells are highly effective sentinel cells, found close to blood vessels and especially common sites of potential infection, such as the skin, airways and gastrointestinal tract. Mast cells participate actively in the innate immune responses to many pathogens through a broad spectrum of mediators that can be selectively generated. They also have a role as innate effector cells in enhancing the earliest processes in the development of acquired immune responses. Studies of bacterial and parasitic models have revealed mast cell dependent regulation of effector cell recruitment, mucosal barrier function and lymph node hypertrophy. An important role for mast cells in viral infection is also implied by several in vivo and in vitro studies. There are multiple direct and indirect pathways by which mast cells can be selectively activated by pathogens including Toll-like receptors, co-receptors and complement component receptors. Understanding the mechanisms and scope of the contribution of mast cells to host defence will be crucial to regulating their activity therapeutically.

We explore the controversial issue of the role of eosinophils in host defense against helminthic parasites using the established Schistosoma mansoni infection model in 2 novel mouse models of eosinophil lineage ablation (DeltadblGATA and TgPHIL). No eosinophils were detected in bone marrow of infected DeltadblGATA or TgPHIL mice, despite the fact that serum IL-5 levels in these infected mice exceeded those in infected wild type by approximately 4-fold. Liver granulomata from infected DeltadblGATA and TgPHIL mice were likewise depleted of eosinophils compared with those from their respective wild types. No eosinophil-dependent differences in granuloma number, size, or fibrosis were detected at weeks 8 or 12 of infection, and differential accumulation of mast cells was observed among the DeltadblGATA mice only at week 12. Likewise, serum levels of liver transaminases, alanine aminotransferase (ALT), and aspartate aminotransferase (AST) increased in all mice in response to S mansoni infection, with no eosinophil-dependent differences in hepatocellular damage observed. Finally, eosinophil ablation had no effect on worm burden or on egg deposition. Overall, our data indicate that eosinophil ablation has no impact on traditional measures of disease in the S mansoni infection model in mice. However, eosinophils may have unexplored immunomodulatory contributions to this disease process.

The role of dermal mast cells (DMC) in the host resistance to ticks has been studied but it is not totally explained yet. Studies have proposed that zebuine cattle breeds, known as highly resistant to ticks, have more DMC than taurine breeds. In the present study, we compared the number of adult female ticks Boophilus microplus and the mast cells' countings in the skin of F(2) crossbred Gir x Holstein cattle, before and after tick infestation. F(2) crossbred cattle (n = 148) were divided into seven groups and artificially infested with 1.0 x 10(4) B. microplus larvae and, 21 days afterwards, adult female-fed ticks attached to the skin were counted. Skin biopsies were taken and examined under light microscopy with a square-lined ocular reticulum in a total area of 0.0625 mm(2) in both the superficial and deep dermis. Results demonstrated that infested F(2) crossbred cattle acquired resistance against the cattle-tick B. microplus probably associated to an increase in the dermal mast cell number. It is concluded that the tick infestation may lead to an environmental modification in the dermis of parasitized hosts due to the massive migration of mast cells or their local proliferation.

To evaluate the potential roles of Interleukin-3 (IL-3) and c-Kit, the tyrosine kinase receptor for stem cell factor (SCF), in eosinophil responses in vivo, we examined eosinophil numbers in uninfected or nematode-infected wild-type mice, IL-3-/- mice, and IL-3-/- mice that also have a marked reduction in SCF/c-Kit signaling (ie, Kit(W)/Kit(W-v), IL-3-/- mice). We found no significant differences in the numbers of eosinophils in the blood, bone marrow or various tissues of IL-3-/- vs IL-3+/+ mice, either at baseline or after the induction of bone marrow, blood or tissue eosinophilia in response to infection with Strongyloides venezuelensis (S.v.) or Nippostrongylus brasiliensis (N.b.). However, in mice with markedly impaired SCF/c-Kit signaling, IL-3 contributed significantly to the increased numbers of eosinophils that were observed in multiple tissues during S.v. infection, but not during infection with N.b.

TNF plays important roles in the protection and onset of malaria. Although mast cells are known as a source of TNF, little is known about the relationship between mast cells and pathogenesis of malaria. In this study, mast cell-deficient WBB6F1-W/W(v) (W/W(v)) and the control littermate WBB6F1+/+ (+/+) mice were infected with 1 x 10(5) of Plasmodium berghei ANKA. +/+ mice had lower parasitemia with higher TNF levels, as compared with W/W(v) mice. Diminished resistance in W/W(v) mice was considered to be due to mast cells and TNF. This fact was confirmed by experiments in W/W(v) mice reconstituted with bone marrow-derived mast cells (BMMCs) of +/+ mice or of TNF-/- mice. W/W(v) mice with BMMCs of +/+ mice exhibit lower parasitemia and mortality accompanying significantly higher TNF levels than those of W/W(v) mice. Parasitemia in W/W(v) mice with BMMCs of TNF-/- mice was higher than that in +/+ mice. Activation of mast cells by anti-IgE or compound 48/80 resulted in release of TNF and decrease of parasitemia. In addition, splenic hypertrophy and increased number of mast cells in the spleen were observed after infection in +/+ mice and W/W(v) mice reconstituted with BMMCs of +/+ mice as compared with W/W(v) mice. These findings propose a novel mechanism that mast cells and mast cell-derived TNF play protective roles in malaria.

In order to investigate immunological changes over time in pigs infected with Trichuris suis, we inoculated 40 pigs with 5000 infective T. suis eggs and left 40 pigs as uninfected controls. Equal numbers of pigs from both groups were sacrificed every other week from 1 to 11 weeks p.i. At necropsy tissue samples were collected from all pigs and their worm burdens were determined. In the proximal colon of T. suis-infected pigs infiltration of eosinophils peaked 5 weeks p.i. and mast cell infiltration developed from 5 to 11 weeks p.i. Histological evaluation of the proximal colon revealed that the presence of T. suis was closely associated with intestinal histopathological changes such as crypt hyperplasia, goblet cell hyperplasia and a general hypertrophy of mucosa. The crypt lengths were positively associated with worm burdens. Real-time PCR analysis of genes related to immune function indicate a local increased transcription of genes coding for CCR3, ARG1, MUC5AC, IL-4, IL-5, IL-13, FcepsilonR1alpha, and IL-13Ralpha2 and decreased expression of genes coding for iNOS, TNF-alpha, IL-10, CD3epsilon, CD80, CD86, IL-4Ralpha, IL-13Ralpha1 and CD40 in the proximal colon of pigs infected with T. suis. This local T-helper cell Type 2-like gene-expression pattern indicates that the Type 2 immune response characteristic of helminth infections in both mouse and humans also develops in pigs infected with T. suis. The results from this study expand our knowledge of the immunomodulatory effect of T. suis, a parasite that has proven effective in treating inflammatory bowel disease, when its eggs are administered regularly to patients.

Histamine is released in inflammatory reactions and exerts an immunoregulatory function on cells present in the microenvironment. In this study, we compared the effect of histamine on degranulation of mast cells derived from animals bearing a parasitic infection with those from uninfected animals. Peritoneal mast cells (PMC) were obtained 24 days after infection of Wistar rats with Toxocara canis. The degree of degranulation was assessed either morphologically or by measuring the release of beta-hexosaminidase and TNF-alpha. Non-purified PMC or mast cells immunomagnetically purified with mAb AA4 were used. An increase in degranulation of non-purified mast cells from infected animals was observed after incubation with histamine in vitro or when histamine was injected into the peritoneal cavity. When a purified mast cell population was used, this effect was no longer observed. Supernatants from spleen cells stimulated with histamine induced degranulation of purified mast cells, and again, this was potentiated with PMC from infected animals. However, when supernatants from peritoneal macrophages similarly stimulated were used, a reduction in the degranulation of PMC from infected animals was observed. Our results suggest that histamine may act as a regulator of mast cell degranulation, thus modulating inflammatory responses due to infection with certain parasites.