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IL-5 is the most potent activator of eosinophils and is produced by Th2 cells and ILC2s. A role for IL-5 in eosinophil extracellular trap cell death, i.e., a proinflammatory cell death, has also been reported. Mepolizumab and benralizumab are humanized mAbs that target IL-5 and the IL-5 receptor α, respectively, and their therapeutic efficacy for severe asthma has been established. Although consistent differences in the efficacies of those drugs have not been proven, benralizumab extensively depleted eosinophils via Ab-dependent cell-mediated cytotoxicity. Blood eosinophil count, but not FeNO or IgE, is the best-established predictive biomarker of the efficacy of anti-IL-5 treatment. Regarding the choice of biologics, the balance between blood eosinophil count and FeNO, indication of comorbidities, longitudinal safety, and interval of injection should be considered. Mepolizumab was also effective in maintaining the remission of refractory eosinophilic granulomatous polyangiitis. Moreover, mepolizumab decreased the proportion of patients who required surgery and lowered the nasal polyp score in patients with chronic rhinosinusitis with nasal polyps; a further extensive trial is currently under way. In a phase II benralizumab study performed in Japan, no significant effect on nasal polyp score at week 12 was observed, suggesting a requirement for longer treatment. In this review, the role of IL-5 in eosinophil biology and the current status of anti-IL-5 therapy are discussed. The longitudinal safety of anti-IL-5 therapy has been increasingly established, and this strategy will be continuously indicated for eosinophilic diseases as a specific treatment for eosinophilic inflammation. Keywords: Benralizumab, Chronic rhinosinusitis with nasal polyps, Eosinophils, IL-5, Mepolizumab

Introduction A recent study from our laboratory demonstrated a number of neurobehavioral abnormalities in mice colony injected with a mouse-weight equivalent dose of all vaccines that are administered to infants in their first 18 months of life according to the U. S. pediatric vaccination schedule. Cytokines have been studied extensively as blood immune and inflammatory biomarkers, and their association with neurodevelopmental disorders. Given the importance of cytokines in early neurodevelopment, we aimed to investigate the potential post-administration effects of the U. S. pediatric vaccines on circulatory cytokines in a mouse model. In the current study, cytokines have been assayed at early and late time points in mice vaccinated early in postnatal life and compared with placebo controls. Materials and methods Newborn mouse pups were divided into three groups: i) vaccine (V1), ii) vaccine ​× ​3 (V3) and iii) placebo control. V1 group was injected with mouse weight-equivalent of the current U. S. pediatric vaccine schedule. V3 group was injected with same vaccines but at triple the dose and the placebo control was injected with saline. Pups were also divided according to the sampling age into two main groups: acute- and chronic-phase group. Blood samples were collected at postnatal day (PND) 23, two days following vaccine schedule for the acute-phase group or at 67 weeks post-vaccination for the chronic-phase groups. Fifteen cytokines were analyzed: GM-CSF, IFN-γ, IL-1β, IL-2, IL-4, IL-5, IL-6, IL-9, IL-10, IL-12p70, IL-13, IL-17A, MCP-1, TNF-α, and VEGF-A. Wilcoxon Rank Sum test or unpaired Student's t-test was performed where applicable. Results IL-5 levels in plasma were significantly elevated in the V1 and V3 group compared with the control only in the acute-phase group. The elevation of IL-5 levels in the two vaccine groups were significant irrespective of whether the sexes were combined or analyzed separately. Other cytokines (VEGF-A, TNF-α, IL-10, MCP-1, GM-CSF, IL-6, and IL-13) were also impacted, although to a lesser extent and in a sex-dependent manner. In the acute-phase group, females showed a significant increase in IL-10 and MCP-1 levels and a decrease in VEGF-A levels in both V1 and V3 group compared to controls. In the acute-phase, a significant increase in MCP-1 levels in V3 group and CM-CSF levels in V1 and V3 group and decrease in TNF-α levels in V1 group were observed in treated males as compared with controls. In chronic-phase females, levels of VEGF-A in V1 and V3 group, TNF-α in V3 group, and IL-13 in V1 group were significantly decreased in contrast with controls. In chronic-phase males, TNF-α levels were significantly increased in V1 group and IL-6 levels decreased in V3 group in comparison to controls. The changes in levels of most tested cytokines were altered between the early and the late postnatal assays. Conclusions IL-5 levels significantly increased in the acute-phase of the treatment in the plasma of both sexes that were subjected to V1 and V3 injections. These increases had diminished by the second test assayed at week 67. These results suggest that a profound, albeit transient, effect on cytokine levels may be induced by the whole vaccine administration supporting our recently published observations regarding the behavioral abnormalities in the same mice. These observations support the view that the administration of whole pediatric vaccines in a neonatal period may impact at least short-term CNS functions in mice.

Drug-induced hypersensitivity syndrome (DIHS), also known as drug reaction with eosinophilia and systemic symptoms (DRESS), is a severe reaction to medications that presents with rash, fever, and lymphadenopathy. Patients typically have eosinophilia and end-organ damage, most commonly to the kidneys or liver. If the heart is involved, either hypersensitivity myocarditis or acute necrotizing eosinophilic myocarditis (ANEM) can occur; the former is often reversible, and the latter is usually fatal.1 DIHS can persist for months after drug withdrawal, and different organ systems can be affected at different times. Symptoms can persist for a year or more.1 DIHS is treated with high doses of corticosteroids, which may be administered for months. DIHS is a type IV hypersensitivity reaction resulting in a T helper cell 2 (Th2)–predominant immune response with recruitment and activation of eosinophils. Interleukin 5 (IL-5), an eosinophil activator, and eosinophil chemokines, C-C motif chemokine ligand (CCL)17 and CCL22, are involved in DIHS and other eosinophilic disorders.2, 3, 4, 5, 6 In DIHS, other cytokines including IL-6, IL-10, and IL-13 are also thought to play a role in pathogenesis.7, 8 IL-5 blockers can be used to treat some eosinophilic disorders but these agents do not block these other pathogenic cytokines. However, all of these cytokines rely on the Janus kinase–signal transducer and activator of transcription (JAK-STAT) pathway and can be simultaneously targeted using JAK inhibitors. It is not known whether molecularly targeted small molecule inhibitors are effective or work rapidly enough to treat severe drug reactions such as DIHS. Here we report 2 consecutive patients with severe DIHS with myocardial involvement treated with the JAK inhibitor tofacitinib.

Visual Abstract, Highlights • There is strong experimental evidence that IL-5 has a protective role in atherosclerosis but the clinical importance of this remains poorly studied. • In a prospective study involving 696 subjects with a follow-up of close to 17 years we show that baseline plasma levels of IL-5 do not predict risk for coronary events and stroke. • However, subjects with high levels of IL-5 were less likely to have a carotid plaque at the baseline investigation. • Experimental studies using a shear stress-modifying cast to the carotid artery of Apoe−/− mice deficient for IL-5 showed that lack of IL-5 was associated with increased plaque formation at sites of oscillatory blood flow. • The findings are in line with previous experimental observations of an atheroprotective role of IL-5 but do not support the use of IL-5 measurement in cardiovascular risk prediction., Summary Experimental studies have suggested an atheroprotective role of interleukin (IL)-5 through the stimulation of natural immunoglobulin M antibody expression. In the present study we show that there are no associations between baseline levels of IL-5 and risk for development of coronary events or stroke during a 15.7 ± 6.3 years follow-up of 696 subjects randomly sampled from the Malmö Diet and Cancer study. However, presence of a plaque at the carotid bifurcation was associated with lower IL-5 and IL-5 deficiency resulted in increased plaque development at sites of oscillatory blood flow in Apoe−/− mice suggesting a protective role for IL-5 in plaque development.

Background: Asthma often coexists with chronic rhinosinusitis (CRS). Recent studies revealed that sinus inflammation in asthmatic patients was related to eosinophilic inflammation. However, the relationship between the severity of CRS and four different sputum inflammatory phenotypes as defined by the proportion of eosinophils and neutrophils is unknown. The aim of this study was to examine the impact of the severity of CRS on lower airway and systemic inflammation in asthmatic patients. Methods: We enrolled 57 adult asthmatic patients who underwent sinus computed tomography (CT). The severity of CRS was evaluated by the Lund-Mackay score (LMS). The induced sputum inflammatory phenotype was defined by eosinophils (≥/

Long-chain polyunsaturated fatty acids (LCPUFAs) and the gut microbiota individually exert notable effects on asthma. However, it remains unknown whether LCPUFAs modulate the gut microbial composition. Twenty-four male BALB/c mice were randomly assigned to control (saline), asthma (ovalbumin (OVA)), and LCPUFAs groups (OVA plus LCPUFAs). The enhanced pause value was observed to decrease upon the administration of LCPUFAs in mice challenged with methacholine (12.5, 25, and 50 g/mL). LCPUFAs treatment decreased the number of eosinophils in BALF compared to that in non-treated asthmatic mice. The interleukin 5 levels in BALF and the airway PAS scores decreased after the asthmatic mice were treated with LCPUFAs. The treatment markedly reversed the imbalances in the gut microbial composition, as evidenced by the beta diversity analysis, and decreased the relative abundance of Akkermansia. These findings suggested that LCPUFAs modulated the gut microbial composition and improved airway pathological features in mice with OVA-induced asthma.

Eosinophilic cystitis is a rare form of interstitial cystitis. It can be chronic and debilitating due to urinary frequency, dysuria, incontinence, and frequent urinary tract infections. Prior attempts at treatment have included oral and intravesical steroids, antispasmodics, and antibiotics when indicated. Treatment of eosinophilic disorders has recently been improved with the use of monoclonal antibodies directed at interleukin 5. We report here a case of eosinophilic cystitis treated with the interleukin 5 antagonist, benralizumab. The patient had significant improvement in both quality of life measures and biopsy findings.

The activation mechanism of chimeric antigen receptor (CAR)-engineered T cells may differ substantially from T cells carrying native T cell receptor, but this difference remains poorly understood. We present the first comprehensive portrait of single-cell level transcriptional and cytokine signatures of anti-CD19/4-1BB/CD28/CD3ζ CAR-T cells upon antigen-specific stimulation. Both CD4+ helper T (TH) cells and CD8+ cytotoxic CAR-T cells are equally effective in directly killing target tumor cells and their cytotoxic activity is associated with the elevation of a range of TH1 and TH2 signature cytokines, e.g., interferon γ, tumor necrotic factor α, interleukin 5 (IL5), and IL13, as confirmed by the expression of master transcription factor genes TBX21 and GATA3. However, rather than conforming to stringent TH1 or TH2 subtypes, single-cell analysis reveals that the predominant response is a highly mixed TH1/TH2 function in the same cell. The regulatory T cell activity, although observed in a small fraction of activated cells, emerges from this hybrid TH1/TH2 population. Granulocyte-macrophage colony stimulating factor (GM-CSF) is produced from the majority of cells regardless of the polarization states, further contrasting CAR-T to classic T cells. Surprisingly, the cytokine response is minimally associated with differentiation status, although all major differentiation subsets such as naïve, central memory, effector memory, and effector are detected. All these suggest that the activation of CAR-engineered T cells is a canonical process that leads to a highly mixed response combining both type 1 and type 2 cytokines together with GM-CSF, supporting the notion that polyfunctional CAR-T cells correlate with objective response of patients in clinical trials. This work provides new insights into the mechanism of CAR activation and implies the necessity for cellular function assays to characterize the quality of CAR-T infusion products and monitor therapeutic responses in patients. Keywords: Single-cell transcriptomics, Single-cell proteomics, CAR-T, T cell activation

Highlights • IL-5 levels were higher in viral SCAP compared to other etiologies. • Mixed etiology SCAP had the highest but not statistically significant IP-10 values. • There were no significant differences in TNF-α between groups. • Procalcitonin levels were highest in SCAP with mixed etiology., Background The serum cytokine levels among 45 mechanically ventilated, intensive care unit (ICU)-treated severe community-acquired pneumonia (SCAP) patients with known microbial etiology in three different etiology groups were assessed. Methods Blood samples for C-reactive protein (CRP), procalcitonin (PCT), interleukin (IL)-5, IL-6, IL-10, human interferon gamma induced protein (IP)-10, and TNF-α (tumor necrosis factor alpha) were collected at time points 0, 12, 24, 48, 72 and 96 h after study inclusion. Results There were 21 (43%) pure bacterial infections (bacterial group, BG), 5 (10%) pure viral infections (viral group, VG), and 19 (39%) mixed bacterial-viral infections (mixed group, MG) among 45 mechanically ventilated SCAP patients. CRP and PCT levels were significantly higher in the MG and values decreased with time in all groups. PCT differed also in time and group analysis (P = 0.001), the highest being in the MG. IL-5 levels were significantly higher in the VG compared to others (Ptime = 0.001, Pgroup = 0.051 and Ptimexgroup = 0.016). IL-6 and IP-10 levels decreased over time (Ptime = 0.003 and Ptime = 0.021), but there were no differences between groups. Conclusion SCAP patients with viral etiology have higher IL-5 levels. Patients with mixed viral and bacterial group have higher PCT compared to other etiologies.

Background: Epithelial cell-derived IL-33 has an important role in the initiation and activation of innate allergic inflammation. IL-33 acts as a cytokine through the ST2 receptor (ST2L) and it stimulates the production of Th2 cytokines. Soluble ST2 (sST2) may regulate Th2 responses by neutralizing the activity of IL-33. Basophils express ST2L and produce IL-5 in response to IL-33. However, the role of the epithelial cell–basophil interaction and sST2 in IL-5 production remains unclear. Methods: Cultured human bronchial epithelial (hBE33) cells, that contained the human IL-33 gene (i.e., hBE33 cells) and a human basophilic cell line, KU812 cells, were used to study the epithelial cell–basophil interaction in the production of IL-5 induced by HDM. Results: At 15 min after incubation, HDM stimulated the rapid release of IL-33 from cultured hBE33 cells. IL-33 and the supernatant of HDM-treated hBE33 cells stimulated IL-5 production from KU812 cells. Anti-IL-33 antibody and anti-ST2 antibody treatment of KU812 cells suppressed IL-5 production, which had been induced by the supernatant of HDM-treated hBE33 cells. The hBE33 cells secreted sST2 in a time-dependent manner. The production of sST2 by KU812 cells co-cultured with hBE33 cells was significantly increased, compared with KU812 cells cultured with the supernatant of hBE33 cells. Soluble ST2 suppressed IL-5 production by KU812 cells, which was induced by the supernatant of HDM-treated hBE33 cells. Conclusions: Epithelial cell-derived IL-33 promoted IL-5 production by KU812 cells. The subsequently produced sST2 has important roles in regulating Th2 responses. Keywords: Epithelial cell–basophil interaction, IL-5, IL-33, Soluble ST2, Th2 cytokine

Background: In recent years, particularly in China, many Chinese medicines and prescriptions for treating allergic rhinitis have been evaluated for their clinical relevance. Studies have found that numerous herbs and their constituent compounds can significantly alleviate allergic symptoms and are effective treatments for allergic rhinitis. The purpose of this study was to examine the modulatory effect of Tong Qiao nose drops on allergy symptoms and the expression of cytokines in the nasal mucosa of rats with ovalbumin-induced allergic rhinitis. Methods: Sixty healthy male Sprague Dawley rats were randomly divided into three groups (n = 20): negative, control, and experimental. Rats in the control or experimental groups were sensitized with ovalbumin to induce allergic rhinitis. The sensitized rats in the experimental group were subsequently exposed to Tong Qiao nose drops, whereas the sensitized control rats were given saline nose drops. Negative control rats were only treated with saline. Allergic symptoms and the pathologic features of the nasal mucosa were observed. The expression of eotaxin in the mucous membrane of rat nasal septums was detected by immunohistochemical staining, and the expression levels of interleukin (IL)-5 and IL-13 were measured by enzyme-linked immunosorbent assay. Results: The symptom scores for the experimental group were significantly lower than those of control rats (p

Group 2 innate lymphoid cells (ILC2s), previously also known as natural helper cells, nuocytes, or innate helper-2 cells) are recently identified lymphoid cells that lack antigen receptors and belong to the group of innate lymphoid cells (ILCs). Like other ILCs, ILC2s develop from the common lymphoid precursor and depend on Notch signaling and the transcription factors Id2 and GATA-3. Additionally, ILC2 development specifically requires sustained GATA-3 expression and the transcription factors RORα and Bcl11b. ILC2s are strategically distributed along barrier sites that are common sites of invasion or colonization by pathogens and commensals. ILC2s are activated by epithelial cell–derived cytokines (interleukin (IL)-25, IL-33, and thymic stromal lymphopoietin). Analogous to Th2 cells, ILC2s produce type 2 cytokines (mainly IL-5 and IL-13) and are involved in antihelminth immunity, allergic inflammation, and epithelial repair. ILC2s have been implicated in various diseases of man and mice, including allergic asthma, chronic rhinitis, and atopic dermatitis.

Background Recently, a second prostaglandin D 2 (PGD 2 ) receptor, chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2), was identified. Because PGD2 was reported to have chemotactic activity on eosinophils, CRTH2 expressed on eosinophils attracted interest as a receptor associated with eosinophil migration to, and accumulation at, inflammatory sites. To elucidate the mechanism regulating the expression of CRTH2 on eosinophils, the effects of PGD 2 , interleukin (IL)-4, IL-5 and interferon (IFN)-γ on CRTH2 expression were investigated. Methods Blood eosinophils were purified using Percoll and anti-CD16 antibody coated magnetic beads. Eosinophils were incubated with PGD 2 and/or IL-4, IL-5 and IFN-γ. The expression of CRTH2 on eosinophils was measured using a FACScan cytometer (Becton Dickinson Immunocytometry Systems, San Jose, CA, USA). Results Prostaglandin D 2 and IL-5, but not IL-4 and IFN-γ, downregulated the expression of CRTH2 on eosinophils. Furthermore, PGD 2 - and IL-5-induced downregulation of CRTH2 on human eosinophils was inhibited by phenylarsine oxide, a receptor internalization inhibitor. Conclusions These results suggest that PGD 2 and IL-5 regulate CRTH2 expression on eosinophils through CRTH2 internalization. The decreased expression of CRTH2 on tissue eosinophils may make these cells remain at the site of allergic inflammation.

Background and objective: Th9 cells producing interleukin (IL) 9 are novel subset of CD4+ T helper cells, which might contribute to airway inflammation in asthma. Moreover, the effect of IL-9 on eosinophils is still not fully understood. Study aim was to evaluate peripheral blood Th9 cells and eosinophil apoptosis in allergic asthma patients. Materials and methods: Eighteen patients with allergic asthma and fourteen patients with allergic rhinitis were examined. Control group included sixteen healthy subjects. Allergic asthma and rhinitis patients did not use corticosteroids and antihistamines at least for 1 week. Peripheral blood eosinophils and CD4+ cells were isolated by high density gradient centrifugation and magnetic separation. Th9 cells and apoptotic eosinophils were estimated by flow cytometer. Serum IL-9 and IL-5 concentration were determined by ELISA. Results: Peripheral blood Th9 cells percentage was increased in allergic asthma group compared with allergic rhinitis and control group (0.74% ± 0.32% vs. 0.19% ± 0.10% and 0.15% ± 0.08%, respectively, P &lt, 0.05). The same tendency was observed for IL-9 (P &lt, 0.01). Percentage of peripheral blood apoptotic eosinophils was decreased in allergic asthma and allergic rhinitis groups compared with control group (P &lt, 0.05). IL-9 concentration corre- lated with percentage of Th9 cells (r = 0.64, P &lt, 0.05) and negatively with percentage of apoptotic eosinophils in allergic asthma group (r = 0.58, P &lt, 0.05). Negative correlation was found between apoptotic eosinophils count and IL-5 concentration in allergic asthma group (r = 0.76, P &lt, 0.05). Conclusions: Patients with allergic asthma demonstrate increased peripheral blood Th9 cells count and serum IL-9, while eosinophil apoptosis is inversely related to IL-9 concentration.

Eosinophils are multifunctional granulocytes that have a variety of roles in host defense. Under homeostasis, eosinophils can be found in bone marrow, blood, fat, uterus, mammary gland, and intestinal tissue, with the latter being the largest reservoir. During inflammatory conditions, eosinophils home to their target tissues, a process primarily driven by the eotaxin-CCR3 axis, with all of the known putative ligands for CCR3 having been shown to be critical in tissue eosinophilia in mice and in humans. In addition, eosinophil migration is also tightly regulated by the eosinophil’s surface adhesion molecule expression during physiological and pathological conditions, a process regulated by Th2 cytokines. As a key innate and adaptive immunity regulator, the eosinophils is a source of pleotropic cytokines, which can directly regulate structural cells and other immunocytes. In addition, eosinophil-specific granule proteins are strong cytotoxins, as well as members of the RNAase family. Eosinophils also take a role in organ development and metabolism regulation under homeostasis, and orchestrate a series of tissue inflammatory injury along the full length of the gastrointestinal (GI) tract in a variety of eosinophilic GI disorders (referred to by the acronym EGID). As a hallmark for human and murine asthma, the eosinophils has been proved to be a central regulator in asthmatic responses, especially in a subset of patients with “eosinophilic” asthma, as demonstrated with anti-IL-5 therapy, which is now becoming a promising intervention for asthma. Taken together, the eosinophils is both a key regulator and effector that is present in the circulation and mucosal immune system and specialized to launch a Th2-tilted response. Targeting eosinophil development, trafficking, survival, and effector functions may open new avenue of disease-specific intervention.

Interleukin (IL)-3 and IL-5 are both regarded as hematopoietic cytokines, which means they provide positive and negative regulation of differentiation, maturation, survival, proliferation, commitment, and functional activation of hematopoietic progenitor cells. This chapter briefly summarizes the existing knowledge on the impact of these cytokines on hematopoietic malignancies. The chapter will begin by giving the definition of the hematopoietic family of cytokines. The following section points out molecular mechanisms that underlie the link between the activity of these interleukins and features of tumor development. Third, we shall discuss the results of preclinical studies on the role of IL-3 and IL-5 on cancer progression. Furthermore, studies evaluating the prognostic role of these cytokines are considered as well. Finally, we shall shed light on IL-3R and its use as a targeted therapy drug for hematopoietic malignancies.

Aspirin-induced asthma is often accompanied by nasal polyps, in which tissue eosinophils are abundant and activated. However, the mechanism of eosinophil infiltration remains unknown. We encountered two aspirin-induced asthma patients with nasal polyps and investigated eosinophil infiltration into nasal polyp tissue. Eosinophil chemotactic activity of extracts from the nasal polyp was elevated and could be inhibited by 40% with anti-interleukin (IL)-5 antibody. Interleukin-5 was detectable in the extract. The chemotactic activity of peripheral blood eosinophils to recombinant human (rh)IL-5 was increased compared with normal volunteers. Messenger RNA expression for IL-5 in CD3 + lymphocytes for polyp tissue was detected using the reverse transcription-polymerase chain reaction. These results suggest that IL-5 from local T lymphocytes may be one of the candidates for recruitment of eosinophils into nasal polyps in aspirin- induced asthma.

Ethnopharmacological relevance Uncaria tomentosa (Willd. ex Roem. & Schult.) DC. (Rubiaceae) is widely used by populations living in South America to treat many ailments associated with inflammatory disorders. Mitraphylline was shown to be the major pentacyclic oxindolic alkaloid present in the bark chloroformic extract of this plant. Its activity against cytokines involved in inflammation process was tested in a murine model in vivo . Materials and methods Mice received mitraphylline once a day for 3 days at 30 mg/kg/day by oral route. Then, they were subjected to bacterial lipopolysaccharide (LPS) endotoxin (15 mg/kg) and the LPS-induced production of 16 different cytokines was determined by Elisa multiplex. Control group received dexamethasone orally at 2 mg/kg/day. Toxicity on K565 cells and murine peritoneal macrophages, in vitro , at doses up to 100 μM was monitored by XTT-colorimetric assay. Results and conclusions For the first time mitraphylline was tested in vivo against a large range of cytokines that play a crucial role in inflammation. Mitraphylline inhibited around 50% of the release of interleukins 1α, 1β, 17, and TNF-α. This activity was similar to dexamethasone. It also reduced almost 40% of the production of interleukin 4 (IL-4) while the corticoid did not. Lastly it did not show any toxicity on K565 cells nor murine macrophages at doses up to 100 μM.

Mucosal immunity is the study of the immune system associated with mucosal sites such as the gut mucosa that comprises Peyer’s patches (PPs), intestinal lamina propria, intestinal intraepithelium, cryptopatches, isolated lymphoid follicles in the gut antimesenteric wall, and the mesenteric lymph nodes. All immune cells can be found in the different compartments of the gut-associated lymphoid tissues. Either IgA precursors in the PPs or IgA plasmablasts or plasma cells in the lamina propria are the most common B cells found in the gut. T cells with undoubtedly thymic origin can be found in PPs and in the lamina propria, and their presence is in part related to the regulation of the differentiation of IgA precursors. T cells in the intraepithelium have either a thymic or extrathymic origin. Secretory IgA found in the gut can neutralize not only food antigens and commensal bacteria but also pathogens.

Interleukin-5 (IL-5) is an interdigitating homodimeric glycoprotein that is initially identified by its ability to support the in vitro growth and differentiation of mouse B cells and eosinophils. IL-5 transgenic mouse shows two predominant features, remarkable increase in B-1 cells resulting in enhanced serum antibody levels, predominantly IgM, IgA, and IgE classes and in expansion of eosinophil numbers in the blood and eosinophil infiltration into various tissues. Conversely, mice lacking a functional gene for IL-5 or IL-5 receptor alpha chain (IL-5Ralpha) display a number of developmental and functional impairments in B cells and eosinophils. IL-5 receptor (IL-5R) comprises alpha and betac chains. IL-5 specifically binds to IL-5Ralpha and induces the recruitment of betac to IL-5R. Although precise mechanisms on cell-lineage-specific IL-5Ralpha expression remain elusive, several transcription factors including Sp1, E12/E47, Oct-2, and c/EBPbeta have been shown to regulate its expression in B cells and eosinophils. JAK2 and JAK1 tyrosine kinase are constitutively associated with IL-5Ralpha and betac, respectively, and are activated by IL-5 stimulation. IL-5 activates at least three different signaling pathways including JAK2/STAT5 pathway, Btk pathway, and Ras/ERK pathway. IL-5 is one of key cytokines for mouse B cell differentiation in general, particularly for fate-determination of terminal B cell differentiation to antibody-secreting plasma cells. IL-5 critically regulates homeostatic proliferation and survival of and natural antibody production by B-1 cells, and enhances the AID and Blimp-1 expression in activated B-2 cells leading to induce mu to gamma1 class switch recombination and terminal differentiation to IgM- and IgG1-secreting plasma cells, respectively. In humans, major target cells of IL-5 are eosinophils. IL-5 appears to play important roles in pathogenesis of asthma, hypereosinophilic syndromes, and eosinophil-dependent inflammatory diseases. Clinical studies will provide a strong impetus for investigating the means of modulating IL-5 effects. We will discuss the role of IL-5 in the link between innate and acquired immune response, particularly emphasis of the molecular basis of IL-5-dependent B cell activation, allergen-induced chronic inflammation and hypereosinophilic syndromes on a novel target for therapy.

CCR3, a receptor for chemokines such as eotaxin-1,-2,-3, MCP-2,-3,-4, and RANTES, is expressed on the surface of eosinophils, mast cells, basophils, and Th2 lymphocytes and, intracellularly, in mast cells. In addition, CCR3 is also found on dendritic cells, astrocytes, and microglial cells in the brain. CCR3 plays an important role in the pathology of acute and chronic inflammatory conditions such as allergic rhinitis, asthma, and airway hyperresponsiveness (AHR), and seasonal conjunctivitis. CCR3 mediates recruitment of eosinophils, basophils, and Th2 lymphocytes to the site of inflammation. CCR3 in and/or on mast cells also mediates trafficking of progenitors, selective programming of mast cell phenotype and effector function, and differentiation and selective development of mast cells to different subtypes. Therefore, CCR3 constitutes an attractive target for therapeutic intervention.

Interleukin-5 (IL-5) is a cytokine secreted principally by activated helper T cells of the T-helper-2 (Th2) subset. IL-5 is a short chain helical bundle cytokine structurally similar to IL-3, IL-4, and granulocyte-macrophage colony-stimulating factor. The IL-5 gene is tightly linked with the IL-4 and IL-13 genes in a Th2 cytokine gene cluster on chromosome 5q, and the expression of these genes is coordinately regulated. The biology of IL-5 has been best studied in the context of asthma in humans and allergic airway inflammation in mouse models. IL-5 directly mediates eosinophilic inflammation by stimulating the differentiation, proliferation, recruitment, survival, and activity of eosinophils. Eosinophils release granule proteins and leukotrienes that are hypothesized to contribute to airway hyperreactivity and epithelial damage in allergic asthma. However, recent studies indicate that the immunopathogenic role of IL-5 and eosinophils in asthma is not clear.

Mast cells and basophils develop from pluripotential stem cells in the bone marrow. Mast cells migrate into tissue, where they mature into resident tissue mast cells. In contrast, basophils are resident in the circulation and migrate into tissue as part of an allergic response. Following activation, both cell types can degranulate, releasing preformed mediators from their granules and synthesizing lipid mediators and cytokines. Mast cell and basophil degranulation is classically mediated by cross-linking of IgE bound to the high-affinity IgE receptor, but there is increasing recognition that several mechanisms can result in degranulation of these cells. Mast cells have an important role in the immune response to infections, and both mast cells and basophils play a pivotal role in the allergic response and are implicated in the pathogenesis of a number of respiratory diseases, particularly asthma and allergic rhinitis.

This chapter reviews the role of mucosal effector cells, including eosinophils, mast cells, and Th2-type cells, in the development of allergic reactions in the gastrointestinal tract. Mucosal eosinophils, mast cells, and T cells play a critical role in the development of gastrointestinal allergic reactions. They have also elucidated the complex cell-to-cell interactions involved in the induction and regulation of mucosal cell-mediated allergic diseases. Eosinophils are multifunctional leukocytes involved in the pathogenesis of allergic disorders. Aberrant eosinophil accumulation in the gastrointestinal tissues is often associated with serious clinical symptoms such as—gastric dysmotility, malabsorption, cachexia, or diarrhea. Eosinophils can potentially initiate antigen-specific immune responses by mimicking antigen-presenting cells. In this regard, eosinophils express major histocompatibility (MHC) class II and costimulatory molecules, such as CD40, CD80, and CD86. Mast cells are the main effector cells in the development of IgE-mediated allergic responses. The pathologic processes of mucosal allergic reactions are known to be mediated by T helper (Th)2-type cells, which preferentially produce IgE-enhancing cytokines such as interleukin (IL)-4 and IL-13.

This chapter deals with interleukin-5, which is the highly conserved member of a group of evolutionary related cytokines which are associated with eosinophilia. It plays an essential role in promoting growth, differentiation, survival, and activation of eosinophils. Thus, it is important to understand the mechanisms of IL-5 regulation, and its activities on eosinophils. To date, most studies have focused on the regulation of the IL-5 gene. While many findings have been made, the complete mechanism of IL-5 regulation has yet to be understood. More studies on the IL-5 gene, protein, and receptor are needed to provide a better understanding of its functions and how it may be specifically regulated for the therapeutic purposes.

Publisher Summary The transcriptional regulation of IL-4, IL-5 and GM-CSF is a very complex process involving interactions between different cisacting elements and transcription factors. It is important to note that NF-AT appears to be required for the efficient activation of all of these genes in T cells. This is interesting because NF-AT is also essential for the activation of IL-2, a Thl cytokine. The NFAT complex is a family of related proteins (NFAT-1, -2, -3, -4) and it will be interesting to identify the role of each NF-AT family member in the co-ordinated expression of these cytokines, especially in the light of the results from the NFATp knock-out mouse showing that IL-2 is expressed normally. Similarly, elucidation of the functions of the palindromic elements has been recently described, and identification of the factors that bind to them, are central to determining the mechanisms that control the expression of these cytokines.

Publisher Summary This chapter quantitatively evaluates interleukin 5 (IL-5) gene expressions in the bronchoalveolar lavage (BAL) cells of patients with asthma. For this purpose, a method has been used that was sensitive, accurate, rapid, and easy to execute. Quantitative polymerase chain reaction (PCR) following the transcription of messenger RNA (mRNA) to complementary DNA (cDNA) is a sensitive method for evaluating cytokine mRNA expression in cells. There are two general methods of quantitative PCR: competitive and noncompetitive. Considerable emphasis has been paid to the competitive method of quantitative PCR because this method is internally controlled and is thought to have the ability to reduce tube-to-tube variation of PCR products. In contrast to the competitive method, noncompetitive method is relatively simple and rapid. However, the accuracy of the noncompetitive method, relative to the competitive method (the gold standard method) is not known. The two methods of quantitative PCR utilizing three test molecules and two reference molecules are compared in the chapter. Experimental data indicate that the values obtained by the noncompetitive method of quantitating IL-5 cDNA levels are comparable to those of the competitive method of quantitative PCR.

Publisher Summary This chapter summarizes the recent progress made in the discovery of modulators of cytokine function with the emphasis on the activity of small molecules and also discusses the clinical use of specific biologicals such as antibodies, soluble receptors, or recombinant cytokines. Interleukin 1 (IL-1), which plays a central role in both inflammatory and immunological responses and has been implicated in a wide range of human diseases, exis,ts in two different forms, IL-1α and IL-1β. Interleukin 2 (IL-2) plays an integral role in the clonal expansion of T-lymphocytes after antigen stimulation. In addition, it stimulates the growth and differentiation of a variety of other lymphocytes, including B cells, natural killer cells, and lymphokine-activated killer cells. The efficacy of IL-2 has been investigated in a number of cancerous states. Interleukin 3 is a 23 kDa glycoprotein, whose general function is to induce proliferation of early hematopoietic progenitor cells. Interleukin 4 is a 20 kDa peptide, which plays a key role in B-cell growth, and is the sole cytokine responsible for initiation of IgE synthesis, implicating it in allergic diseases and parasitic infections. Its immunoregulatory functions and potential application in cancer therapy have been reviewed. Interleukin 5 plays a key role in eosinophil and B-cell proliferation and differentiation. Interleukin 6 is a major mediator of the acute phase response to infection or injury. Interleukin 7 is a 25 kDa protein derived from stromal cells. It stimulates the proliferation of pre-B cells, thymocytes, and mature T cells. Interleukin 8 is a monocyte-derived chemotactic factor for neutrophils. Tumor necrosis factor-α plays a central role in host defense mechanisms and has been implicated in shock, chronic inflammation, and other autoimmune diseases. These studies can provide not only the pharmacological tools but also the future drugs for the treatment of immunological, inflammatory, and oncological diseases.

Interleukin 6 (BSF-2/26kD protein/IFN-s 2/HPGF/HSF) is a multifunctional cytokine produced by both lymphoid and non-lymphoid cells. Both high and low affinity IL-6 specific receptors were identified and the cDNA encoding IL-6-R was cloned. The data showed that IL-6 receptor is a member of the immunoglobulin superfamily. IL-6 was demonstrated to be an essential factor for immunoglobulin production by B cells. The results suggested that the deregulation is involved in the pathogenesis of autoimmne diseases and the oncogenesis of multiple myeloma.

Human mature eosinophils have been cultured for up to 2 weeks by coculture with endothelial cells, or by culture in enriched medium supplemented with interleukin 3, interleukin 5, granulocyte/macrophage colony-stimulating factor, or the serum of a patient with the idiopathic hypereosinophilic syndrome. Compared to the freshly isolated eosinophils, the cultured eosinophils underwent phenotypic changes characterized by enhanced calcium ionophore-induced leukotriene C4 generation, enhanced cytotoxicity for antibody-coated larvae of Schistosoma mansoni and hypodensity as defined by sedimentation analysis. These findings and an integrated view of the regulation of eosinophil post-mitotic phenotype are presented.