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Introduction: Staphylococcus epidermidis is a commensal bacterium ubiquitously present on human skin. This species is considered as a key member of the healthy skin microbiota, involved in the defense against pathogens, modulating the immune system, and involved in wound repair. Simultaneously, S. epidermidis is the second cause of nosocomial infections and an overgrowth of S. epidermidis has been described in skin disorders such as atopic dermatitis. Diverse isolates of S. epidermidis co-exist on the skin. Elucidating the genetic and phenotypic specificities of these species in skin health and disease is key to better understand their role in various skin conditions. Additionally, the exact mechanisms by which commensals interact with host cells is partially understood. We hypothesized that S. epidermidis isolates identified from different skin origins could play distinct roles on skin differentiation and that these effects could be mediated by the aryl hydrocarbon receptor (AhR) pathway. Methods: For this purpose, a library of 12 strains originated from healthy skin (non-hyperseborrheic (NH) and hyperseborrheic (H) skin types) and disease skin (atopic (AD) skin type) was characterized at the genomic and phenotypic levels. Results and discussion: Here we showed that strains from atopic lesional skin alter the epidermis structure of a 3D reconstructed skin model whereas strains from NH healthy skin do not. All strains from NH healthy skin induced AhR/OVOL1 path and produced high quantities of indole metabolites in co-culture with NHEK; especially indole-3-aldehyde (IAld) and indole-3-lactic acid (ILA); while AD strains did not induce AhR/OVOL1 path but its inhibitor STAT6 and produced the lowest levels of indoles as compared to the other strains. As a consequence, strains from AD skin altered the differentiation markers FLG and DSG1. The results presented here, on a library of 12 strains, showed that S. epidermidis originated from NH healthy skin and atopic skin have opposite effects on the epidermal cohesion and structure and that these differences could be linked to their capacity to produce metabolites, which in turn could activate AHR pathway. Our results on a specific library of strains provide new insights into how S. epidermidis may interact with the skin to promote health or disease. [ABSTRACT FROM AUTHOR]

Complex interactions between the host and the gut microbiota govern intestinal homeostasis but remain poorly understood. Here we reveal a relationship between gut microbiota and caspase recruitment domain family member 9 (CARD9), a susceptibility gene for inflammatory bowel disease (IBD) that functions in the immune response against microorganisms. CARD9 promotes recovery from colitis by promoting interleukin (IL)-22 production, and Card9[sup.-/-] mice are more susceptible to colitis. The microbiota is altered in Card9[sup.-/-] mice, and transfer of the microbiota from Card9[sup.-/-] to wild-type, germ-free recipients increases their susceptibility to colitis. The microbiota from Card9[sup.-/-] mice fails to metabolize tryptophan into metabolites that act as aryl hydrocarbon receptor (AHR) ligands. Intestinal inflammation is attenuated after inoculation of mice with three Lactobacillus strains capable of metabolizing tryptophan or by treatment with an AHR agonist. Reduced production of AHR ligands is also observed in the microbiota from individuals with IBD, particularly in those with CARD9 risk alleles associated with IBD. Our findings reveal that host genes affect the composition and function of the gut microbiota, altering the production of microbial metabolites and intestinal inflammation., Author(s): Bruno Lamas [1, 2, 3, 4, 5, 6]; Mathias L Richard [5, 6]; Valentin Leducq [1, 2, 3, 4, 6]; Hang-Phuong Pham [7]; Marie-Laure Michel [5, 6]; Gregory Da [...]

In spite of their precipitous encounter with the environment, newborn infants cannot readily mount T helper type 1 ([T.sub.H].1) cell antibacterial and antiviral responses. Instead, they show skewing toward [T.sub.H].2 responses, which, together with immunoregulatoiy functions, are thought to limit the potential for inflammatory damage, while simultaneously permitting intestinal colonization by commensals (1-3). However, these collective capabilities account for relatively few T cells. Here we demonstrate that a major T cell effector function in human newborns is interleukin-8 (CXCL8) production, which has the potential to activate antimicrobial neutrophils and γδ T cells. CXCL8 production was provoked by antigen receptor engagement of T cells that are distinct from those few cells producing [T.sub.H]1, [T.sub.H]2 and [T.sub.H]17 cytokines, was co-stimulated by Toll-like receptor signaling, and was readily apparent in preterm babies, particularly those experiencing neonatal infections and severe pathology. By contrast, CXCL8-producing T cells were rare in adults, and no equivalent function was evident in neonatal mice. CXCL8 production counters the widely held view that T lymphocytes in very early life are intrinsically anti-inflammatory, with implications for immune monitoring, immune interventions (including vaccination) and immunopathologies. It also emphasizes qualitative distinctions between infants' and adults' immune systems., Although early survival of preterm infants has improved, late-onset septicemias or severe complications such as necrotizing enterocolitis (NEC) have increased as causes of mortality and long-term morbidity (4-6). Yet relatively [...]

Food processes use different microorganisms, from bacteria to fungi. Yeast strains have been extensively studied, especially Saccharomyces cerevisiae. However, to date, very little is known about the potential beneficial effects of molds on gut health as part of gut microbiota. We undertook a comprehensive characterization of five mold strains, Penicillium camemberti, P. nalgiovense, P. roqueforti, Fusarium domesticum, and Geotrichum candidum used in food processes, on their ability to trigger or protect intestinal inflammation using in vitro human cell models and in vivo susceptibility to sodium dextran sulfate-induced colitis. Comparison of spore adhesion to epithelial cells showed a very wide disparity in results, with F. domesticum and P. roqueforti being the two extremes, with almost no adhesion and 20% adhesion, respectively. Interaction with human immune cells showed mild pro-inflammatory properties of all Penicillium strains and no effect of the others. However, the potential anti-inflammatory abilities detected for G. candidum in vitro were not confirmed in vivo after oral gavage to mice before and during induced colitis. According to the different series of experiments carried out in this study, the impact of the spores of these molds used in food production is limited, with no specific beneficial or harmful effect on the gut. [ABSTRACT FROM AUTHOR]

Invariant natural killer T (iNKT) cells constitute a subpopulation of T cells that recognize glycolipids presented by CDld molecules. They are characterized by their prompt production of interleukin-4 (IL-4) and interferon-[gamma] (IFN-[gamma]), which enables them to modulate diverse immune responses. Recently, we enlarged this concept by identifying a distinct IL-17-producing iNKT cell subset, named iNKT17 cells. The mechanisms leading to the acquisition of this new iNKT cell activity are unknown. Herein we show that IL-17-producing iNKT cells are already present in the thymus, predominantly among a subset regarded so far as an immature stage of thymic iNKT cell development, the CD1d [tetramer.sup.pos][CD44.sup.pos][NK1.1.sup.neg][CD4.sup.neg] cells. Using EGFP reporter mice, we demonstrate that the transcription factor ROR-[gamma]t is critical for the thymic differentiation of this subset because only [ROR-[gamma]t.sup.pos] iNKT cells are capable of massively secreting IL-17. Moreover, IL-17-producing CD1d [tetramer.sup.pos][CD44.sup.pos][NK1.1.sup.neg][CD4.sup.neg] thymic iNKT cells have reached a mature differentiation stage because they fail to generate other cell subsets in fetal thymic organ culture. Conversely, thymic [ROR-[gamma][t.sup.neg] iNKT cell precursors give rise to progeny, but acquire neither ROR-[gamma]t expression nor the ability to secrete IL-17. In conclusion, our findings demonstrate an alternative thymic pathway leading to the development of iNKT17 cells that requires ROR-[gamma]t expression. thymic precursors | [alpha]-GalCer | CD1d | cytokines

In a recent Science issue, Bousbaine et al. (2022) identified β-N-acetylhexosaminidase, a conserved antigen expressed by commensals that drives expansion and differentiation of intestinal intra-epithelial cells and protects against gut inflammation. [ABSTRACT FROM AUTHOR]

Summary: Antimicrobial peptides secreted by intestinal immune and epithelial cells are important effectors of innate immunity. They play an essential role in the maintenance of intestinal homeostasis by limiting microbial epithelium interactions and preventing unnecessary microbe‐driven inflammation. Pancreatitis‐associated protein (PAP) belongs to Regenerating islet‐derived III proteins family and is a C‐type (Ca+2 dependent) lectin. PAP protein plays a protective effect presenting anti‐inflammatory properties able to reduce the severity of colitis, preserving gut barrier and epithelial inflammation. Here, we sought to determine whether PAP delivered at intestinal lumen by recombinant Lactococcus lactis strain (LL‐PAP) before and after chemically induced colitis is able to reduce the severity in two models of colitis. After construction and characterization of our recombinant strains, we tested their effects in dinitro‐benzenesulfonic‐acid (DNBS) and Dextran sulfate sodium (DSS) colitis model. After the DNBS challenge, mice treated with LL‐PAP presented less severe colitis compared with PBS and LL‐empty‐treated mice groups. After the DSS challenge, no protective effects of LL‐PAP could be detected. We determined that after 5 days administration, LL‐PAP increase butyrate producer's bacteria, especially Eubacterium plexicaudatum. Based on our findings, we hypothesize that a treatment with LL‐PAP shifts the microbiota preventing the severity of colon inflammation in DNBS colitis model. These protective roles of LL‐PAP in DNBS colitis model might be through intestinal microbiota modulation. [ABSTRACT FROM AUTHOR]

Dietary lipids favor the growth of the pathobiont Bilophila wadsworthia, but the relevance of this expansion in metabolic syndrome pathogenesis is poorly understood. Here, we showed that B. wadsworthia synergizes with high fat diet (HFD) to promote higher inflammation, intestinal barrier dysfunction and bile acid dysmetabolism, leading to higher glucose dysmetabolism and hepatic steatosis. Host-microbiota transcriptomics analysis reveal pathways, particularly butanoate metabolism, which may underlie the metabolic effects mediated by B. wadsworthia. Pharmacological suppression of B. wadsworthia-associated inflammation demonstrate the bacterium’s intrinsic capacity to induce a negative impact on glycemic control and hepatic function. Administration of the probiotic Lactobacillus rhamnosus CNCM I-3690 limits B. wadsworthia-induced immune and metabolic impairment by limiting its expansion, reducing inflammation and reinforcing intestinal barrier. Our results suggest a new avenue for interventions against western diet-driven inflammatory and metabolic diseases. [ABSTRACT FROM AUTHOR]

Invariant NKT (iNKT) cells differentiate in the thymus into three distinct lineages defined by their cytokine and transcription factor expression. Signaling lymphocyte activation molecule (SLAM)-associated protein (SAP) is essential for early stages of iNKT cell development, but its role during terminal differentiation of iNKT1, iNKT2, or iNKT17 cells remains unclear. Taking advantage of SAP-deficient mice expressing a Vα14-Jα18 TCRα transgene, we found that SAP is critical not only for IL-4 production but also for the terminal differentiation of IL-4-producing iNKT2 cells. Furthermore, without SAP, the IL-17 producing subset is expanded, while IFN-γ-producing iNKT1 differentiation is only moderately compromised. Lack of SAP reduced the expression of the transcription factors GATA-3 and promyelocytic leukemia zinc finger, but enhanced the levels of retinoic acid receptor-related orphan receptor γt. In the absence of SAP, lineage commitment was actually shifted toward the emergence of iNKT17 over iNKT2 cells. Collectively, our data unveil a new critical regulatory function for SAP in thymic iNKT cell fate decisions. [ABSTRACT FROM AUTHOR]

Naive CD4 lymphocytes undergo a polarization process in the periphery to become induced Th17 (iTh17) cells. Using retinoic acid-related orphan receptor γt (RORγt)-gfp mice, we found that RORγt and the transcription factor promyelocytic leukemia zinc finger (PLZF) are valuable new markers to identify the recently described natural Th17 (nTh17) cell population. nTh17 cells are thymically committed to promptly produce large amounts of IL-17 and IL-22. In this study, we show that, in addition to responding to TCR cross-linking, nTh17 cells secrete IL-17 and IL-22 when stimulated with IL-23 plus IL-1β, either in recombinant form or in supernatants from TLR4-activated dendritic cells. This innate-like ability of RORγt+ nTh17 cells to respond to TLR4-induced cytokines was not shared by iTh17 cells. The other distinct properties of RORγt+ nTh17 cells are their high expression of PLZF and their absence from lamina propria; iTh17 cells are found therein. RORγt+ nTh17 cells are present in the thymus of germ-free RORγt-gfp and IL-6-/- RORγt-gfp mice, indicating that these cells do not require symbiotic microbiota or IL-6 for their generation. Finally, we found that PLZF+RORγt+ nTh17 cells represent one of the primary IL-17-producing innate-like T cell populations in a TLR7 imiquimod model of psoriasis-like disorder, indicating their involvement in this kind of lesion. Collectively, our results reveal RORγt and PLZF as characteristic markers for identifying nTh17 cells and demonstrate one of their novel properties: the ability to respond promptly to TLR-dependent proinflammatory stimuli without TCR engagement, placing them as members of the innate-like T cell family. [ABSTRACT FROM AUTHOR]

Symptom occurrence at the first ingestion suggests that food allergy may result from earlier sensitization via non-oral routes. We aimed to characterize the cellular populations recruited at various mucosal and immune sites after experimental sensitization though different routes. BALB/cJ mice were exposed to a major allergenic food (peanut) mixed with cholera toxin via the intra-gastric (i.g.), respiratory, cutaneous, or intra-peritoneal (i.p.) route. We assessed sensitization and elicitation of the allergic reaction and frequencies of T cells, innate lymphoid cells (ILC), and inflammatory and dendritic cells (DC) in broncho-alveolar lavages (BAL), lungs, skin, intestine, and various lymph nodes. All cellular data were analyzed through non-supervised and supervised uni/multivariate analysis. All exposure routes, except cutaneous, induced sensitization, but intestinal allergy was induced only in i.g.- and i.p.-exposed mice. Multivariate analysis of all cellular constituents did not discriminate i.g. from control mice. Conversely, respiratory-sensitized mice constituted a distinct cluster, characterized by high local inflammation and immune cells recruitment. Those mice also evidenced changes in ILC frequencies at distant site (intestine). Despite absence of sensitization, cutaneous-exposed mice evidenced comparable changes, albeit less intense. Our study highlights that the initial route of sensitization to a food allergen influences the nature of the immune responses at various mucosal sites. Interconnections of mucosal immune systems may participate in the complexity of clinical manifestations as well as in the atopic march. [ABSTRACT FROM AUTHOR]

Invariant natural killer T (iNKT) cells are a distinct lineage of innate-like T lymphocytes and converging studies in mouse models have demonstrated the protective role of iNKT cells in the development of type 1 diabetes. Recently, a new subset of iNKT cells, producing high levels of the pro-inflammatory cytokine IL-17, has been identified (iNKT17 cells). Since this cytokine has been implicated in several autoimmune diseases, we have analyzed iNKT17 cell frequency, absolute number and phenotypes in the pancreas and lymphoid organs in non-obese diabetic (NOD) mice. The role of iNKT17 cells in the development of diabetes was investigated using transfer experiments. NOD mice exhibit a higher frequency and absolute number of iNKT17 cells in the lymphoid organs as compared with C57BL/6 mice. iNKT17 cells infiltrate the pancreas of NOD mice where they express IL-17 mRNA. Contrary to the protective role of CD4+ iNKT cells, the CD4− iNKT cell population, which contains iNKT17 cells, enhances the incidence of diabetes. Treatment with a blocking anti-IL-17 antibody prevents the exacerbation of the disease. This study reveals that different iNKT cell subsets play distinct roles in the regulation of type 1 diabetes and iNKT17 cells, which are abundant in NOD mice, exacerbate diabetes development. [ABSTRACT FROM AUTHOR]

Background: Idiopathic pulmonary fibrosis is a devastating as yet untreatable disease. We demonstrated recently the predominant role of the NLRP3 inflammasome activation and IL-1β expression in the establishment of pulmonary inflammation and fibrosis in mice. Methods: The contribution of IL-23 or IL-17 in pulmonary inflammation and fibrosis was assessed using the bleomycin model in deficient mice. Results: We show that bleomycin or IL-1β-induced lung injury leads to increased expression of early IL-23p19, and IL-17A or IL-17F expression. Early IL-23p19 and IL-17A, but not IL-17F, and IL-17RA signaling are required for inflammatory response to BLM as shown with gene deficient mice or mice treated with neutralizing antibodies. Using FACS analysis, we show a very early IL-17A and IL-17F expression by RORγt+ γδ T cells and to a lesser extent by CD4αβ+ T cells, but not by iNKT cells, 24 hrs after BLM administration. Moreover, IL-23p19 and IL-17A expressions or IL-17RA signaling are necessary to pulmonary TGFβ1 production, collagen deposition and evolution to fibrosis. Conclusions: Our findings demonstrate the existence of an early IL-1β-IL-23-IL-17A axis leading to pulmonary inflammation and fibrosis and identify innate IL-23 and IL-17A as interesting drug targets for IL-1β driven lung [ABSTRACT FROM AUTHOR]

Allergic asthma is a multifaceted syndrome consisting of eosinophil-rich airway inflammation, bronchospasm, and airway hyper-responsiveness (AHR). Using a mouse model of allergic asthma, we previously reported that invariant NKT (iNKT) cells increase the severity of this disease. Herein, we demonstrate that a single i.v. injection of α-galactosylceramide (α-GalCer), 1 h before the first airway allergen challenge of OVA-sensitized mice, abrogates elicitation of AHR, airway eosinophilia, IL-4 and IL-5 production in bronchoalveolar lavage fluid, and specific anti-OVA IgE antibodies. Further, α-GalCer administered intranasally also strongly inhibited the major symptoms of asthma in sensitized and challenged mice. α-GalCer treatment induces iNKT cell accumulation in the lungs, and shifts their cytokine profile from pro-asthmatic IL-4 to a protective IFN-γ production. The role of IFN-γ from iNKT cells in protection was shown by adoptive transfer of sorted iNKT cells from OVA-sensitized and α-GalCer-treated mice which protected immunized recipients from manifesting asthma by an IFN-γ-dependent pathway. Our findings demonstrate for the first time that α-GalCer administered locally inhibits asthma symptoms, even in predisposed asthmatic mice, through an iNKT cell- and IFN-γ-dependent pathway. See accompanying commentary: [ABSTRACT FROM AUTHOR]

Gut interleukin-17A (IL-17)-producing γδ T cells are tissue-resident cells that are involved in both host defense and regulation of intestinal inflammation. However, factors that regulate their functions are poorly understood. In this study, we find that the gut microbiota represses IL-17 production by cecal γδ T cells. Treatment with vancomycin, a Gram-positive bacterium-targeting antibiotic, leads to decreased production of short-chain fatty acids (SCFAs) by the gut microbiota. Our data reveal that these microbiota-derived metabolites, particularly propionate, reduce IL-17 and IL-22 production by intestinal γδ T cells. Propionate acts directly on γδ T cells to inhibit their production of IL-17 in a histone deacetylase-dependent manner. Moreover, the production of IL-17 by human IL-17-producing γδ T cells from patients with inflammatory bowel disease (IBD) is regulated by propionate. These data contribute to a better understanding of the mechanisms regulating gut γδ T cell functions and offer therapeutic perspectives of these cells. [Display omitted] • The gut microbiota represses IL-17 production by cecal γδ T cells • Short-chain fatty acids repress IL-17- and IL-22-producing γδ T cells • Propionate acts on γδ T cell functionalities by inhibiting histone deacetylase • Propionate represses IL-17 production by human γδ T cells from patients with IBD Dupraz et al. demonstrate that short-chain fatty acids, particularly propionate, reduce IL-17 production by mouse intestinal γδ T cells and human IL-17-producing γδ T cells from patients with inflammatory bowel disease (IBD). These microbiota-derived metabolites act directly on γδ T cells in a histone deacetylase-dependent manner. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article "Induced IL-17-Producing Invariant NKT Cells Require Activation in Presence of TGF-β and IL-1β" by M. Monteiro and colleagues that was published in the previous issue.

Introduction: Antibiotic effects on gut bacteria have been widely studied, but very little is known about the consequences of such treatments on the mycobiota, the fungal part of the microbiota and how the length of administration influences both microbiota. Here, we examined the effect of antibiotics (ATB) on the composition of bacterial and fungal microbiota and how the administration of Saccharomyces boulardii CNCM I-745 influences both microbiota., Methods: In order to get closer to the human microbiota, the mice used in this study were subjected to fecal microbiota transfer (FMT) using human feces and subsequently called human microbiotaassociated (HMA) mice. These mice were then treated with amoxicillinclavulanate antibiotics and supplemented with S. boulardii during and after ATB treatment to understand the effect of the yeast probiotic on both bacterial and fungal microbiota. Bacterial and fungal microbiota analyses were done using 16S and ITS2 rRNA amplicon-based sequencing., Results: We showed that the administration of S. boulardii during ATB treatment had very limited effect on the fungal populations on the long term, once the yeast probiotic has been cleared from the gut. Concerning bacterial microbiota, S. boulardii administration allowed a better recovery of bacterial populations after the end of the ATB treatment period. Additionally, 16S and ITS2 rRNA sequence analysis revealed that 7 additional days of S. boulardii administration (17 days in total) enhanced the return of the initial bacterial equilibrium., Discussion: In this study, we provide a comprehensive analysis of how probiotic yeast administration can influence the fungal and bacterial microbiota in a model of broad-spectrum antibiotherapy., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The original study design was initially discussed between the research group and Biocodex. The decision to submit the data for publication was approved by Biocodex., (Copyright © 2023 Spatz, Wang, Lapiere, Da Costa, Michaudel, Danne, Michel, Langella, Sokol and Richard.)

Objective: The extent to which tryptophan (Trp) metabolism alterations explain or influence the outcome of inflammatory bowel diseases (IBDs) is still unclear. However, several Trp metabolism end-products are essential to intestinal homeostasis. Here, we investigated the role of metabolites from the kynurenine pathway., Design: Targeted quantitative metabolomics was performed in two large human IBD cohorts (1069 patients with IBD). Dextran sodium sulphate-induced colitis experiments in mice were used to evaluate effects of identified metabolites. In vitro, ex vivo and in vivo experiments were used to decipher mechanisms involved. Effects on energy metabolism were evaluated by different methods including Single Cell mEtabolism by profiling Translation inHibition., Results: In mice and humans, intestinal inflammation severity negatively correlates with the amount of xanthurenic (XANA) and kynurenic (KYNA) acids. Supplementation with XANA or KYNA decreases colitis severity through effects on intestinal epithelial cells and T cells, involving Aryl hydrocarbon Receptor (AhR) activation and the rewiring of cellular energy metabolism. Furthermore, direct modulation of the endogenous tryptophan metabolism, using the recombinant enzyme aminoadipate aminotransferase (AADAT), responsible for the generation of XANA and KYNA, was protective in rodent colitis models., Conclusion: Our study identified a new mechanism linking Trp metabolism to intestinal inflammation and IBD. Bringing back XANA and KYNA has protective effects involving AhR and the rewiring of the energy metabolism in intestinal epithelial cells and CD4 + T cells. This study paves the way for new therapeutic strategies aiming at pharmacologically correcting its alterations in IBD by manipulating the endogenous metabolic pathway with AADAT., Competing Interests: Competing interests: HS report lecture fee, board membership, or consultancy from Carenity, AbbVie, Astellas, Danone, Ferring, Mayoly Spindler, MSD, Novartis, Roche, Tillots, Enterome, BiomX, Biose, Novartis,Takeda, Biocodex and is cofounder of Exeliom Biosciences., (© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

We have recently described antitumor properties of Lactobacillus casei BL23 strain in both a mouse allograft model of human papilloma virus (HPV)-induced cancer and dimethylhydrazine-associated colorectal cancer. However, the mechanisms underlying these beneficial effects are still unknown. Interestingly, in vitro cellular models show that this bacterium is able to stimulate the production of high levels of IL-2. Because this cytokine has well-known antitumor properties, we decided to explore its role in the anti-cancer effects of BL23 using the HPV-induced cancer model. We found a negative correlation between IL-2 and tumor size confirming the necessity of IL-2 to protect from tumor development. Then, we blocked IL-2 synthesis using neutralizing monoclonal antibodies in mice that were challenged with lethal levels of tumor cells; this led to a significant reduction in the protective abilities of BL23. Next, we used a genetically modified strain of Lactococcus lactis to deliver exogenous IL-2 to the system, and in doing so, we were able to partially mimic the antitumor properties of BL23. Additionally, we showed the systemic role of T-cells in tumor protection through a negative correlation between tumor size and T-cells subpopulations and an increasement of BL23-specific local Foxp3 levels in tumor-bearing mice. Finally, we observed a negative correlation between tumor size and NK+ cells, but local recruitment of NK cells and cytotoxic activity appeared specific to BL23 treatment. Taken together, our data suggest that IL-2 signaling pathway plays an important role in the anti-tumoral effects of probiotic strain L. casei BL23. These results encourage further investigation in the use of probiotic strains for potential therapeutic applications to clinical practice, in particular for the treatment of colorectal cancer. Furthermore, our approach could be extended and applied to other potential beneficial microorganisms, such as gut microbiota, in order to better understand the crosstalk between microbes and the host.

Invariant natural killer T (iNKT) cells represent a particular subset of T lymphocytes capable of producing several cytokines, which exert regulatory or effector functions, following stimulation of the T cell receptor. In this study, we investigated the influence of iNKT cells on the development of experimental anti-glomerular basement membrane glomerulonephritis (anti-GBM GN). After injection of anti-GBM serum, the number of kidney iNKT cells rapidly increased. iNKT cell-deficient mice (Jalpha18-/-) injected with anti-GBM serum demonstrated worse renal function, increased proteinuria, and greater glomerular and tubular injury compared with similarly treated wild-type mice. We did not detect significant differences in Th1/Th2 polarization in renal tissue that might have explained the severity of disease in Jalpha18-/- mice. Interestingly, expression of both TGF-beta and TGF-beta-induced (TGFBI) mRNA was higher in wild-type kidneys compared with Jalpha18-/- kidneys, suggesting a possible protective role for TGF-beta in anti-GBM GN. Administration of an anti-TGF-beta neutralizing antibody significantly enhanced the severity of disease in wild-type, but not Jalpha18-/-, mice. In conclusion, in experimental anti-GBM GN, iNKT cells attenuate disease severity and TGF-beta has a renoprotective role.

Histamine (HA) is a biogenic amine with multiple activities in the immune system. In this study we demonstrate that histamine-free histidine decarboxylase-deficient (HDC(-/-)) mice present a numerical and functional deficit in invariant NK T (iNKT) cells as evidenced by a drastic decrease of IL-4 and IFN-gamma production. This deficiency was established both by measuring cytokine levels in the serum and intracellularly among gated iNKT cells. It resulted from the lack of HA, because a single injection of this amine into HDC(-/-) mice sufficed to restore normal IL-4 and IFN-gamma production. HA-induced functional recovery was mediated mainly through the H4 histamine receptor (H4R), as assessed by its abrogation after a single injection of a selective H4R antagonist and the demonstration of a similar iNKT cell deficit in H4R(-/-) mice. Our findings identify a novel function of HA through its H4R and suggest that it might become instrumental in modulating iNKT cell functions.

Invariant natural killer T (iNKT) cells are an important source of both T helper type 1 (Th1) and Th2 cytokines, through which they can exert beneficial, as well as deleterious, effects in a variety of inflammatory diseases. This functional heterogeneity raises the question of how far phenotypically distinct subpopulations are responsible for such contrasting activities. In this study, we identify a particular set of iNKT cells that lack the NK1.1 marker (NK1.1(neg)) and secrete high amounts of interleukin (IL)-17 and low levels of interferon (IFN)-gamma and IL-4. NK1.1(neg) iNKT cells produce IL-17 upon synthetic (alpha-galactosylceramide [alpha-GalCer] or PBS-57), as well as natural (lipopolysaccharides or glycolipids derived from Sphingomonas wittichii and Borrelia burgdorferi), ligand stimulation. NK1.1(neg) iNKT cells are more frequent in the lung, which is consistent with a role in the natural immunity to inhaled antigens. Indeed, airway neutrophilia induced by alpha-GalCer or lipopolysaccharide instillation was significantly reduced in iNKT-cell-deficient Jalpha18(-/-) mice, which produced significantly less IL-17 in their bronchoalveolar lavage fluid than wild-type controls. Furthermore, airway neutrophilia was abolished by a single treatment with neutralizing monoclonal antibody against IL-17 before alpha-GalCer administration. Collectively, our findings reveal that NK1.1(neg) iNKT lymphocytes represent a new population of IL-17-producing cells that can contribute to neutrophil recruitment through preferential IL-17 secretion.

Allergic asthma is a multifaceted syndrome consisting of eosinophil-rich airway inflammation, bronchospasm, and airway hyper-responsiveness (AHR). Using a mouse model of allergic asthma, we previously reported that invariant NKT (iNKT) cells increase the severity of this disease. Herein, we demonstrate that a single i.v. injection of alpha-galactosylceramide (alpha-GalCer), 1 h before the first airway allergen challenge of OVA-sensitized mice, abrogates elicitation of AHR, airway eosinophilia, IL-4 and IL-5 production in bronchoalveolar lavage fluid, and specific anti-OVA IgE antibodies. Further, alpha-GalCer administered intranasally also strongly inhibited the major symptoms of asthma in sensitized and challenged mice. Alpha-GalCer treatment induces iNKT cell accumulation in the lungs, and shifts their cytokine profile from pro-asthmatic IL-4 to a protective IFN-gamma production. The role of IFN-gamma from iNKT cells in protection was shown by adoptive transfer of sorted iNKT cells from OVA-sensitized and alpha-GalCer-treated mice which protected immunized recipients from manifesting asthma by an IFN-gamma-dependent pathway. Our findings demonstrate for the first time that alpha-GalCer administered locally inhibits asthma symptoms, even in predisposed asthmatic mice, through an iNKT cell- and IFN-gamma-dependent pathway.