Microbial-induced Th17: superhero or supervillain?

Multifaceted TGF-β signaling, a master regulator: From bench-to-bedside, intricacies, and complexities

Physiological embryogenesis and adult tissue homeostasis are regulated by transforming growth factor-β (TGF-β), an evolutionarily conserved family of secreted polypeptide factors, acting in an autocrine and paracrine manner. The role of TGF-β in inflammation, fibrosis, and cancer is complex and sometimes even contradictory, exhibiting either inhibitory or promoting effects depending on the stage of the disease. Under pathological conditions, especially fibrosis and cancer, overexpressed TGF-β causes extracellular matrix deposition, epithelial-mesenchymal transition, cancer-associated fibroblast formation, and/or angiogenesis. In this review article, we have tried to dive deep into the mechanism of action of TGF-β in inflammation, fibrosis, and carcinogenesis. As TGF-β and its downstream signaling mechanism are implicated in fibrosis and carcinogenesis blocking this signaling mechanism appears to be a promising avenue. However, targeting TGF-β carries substantial risk as this pathway is implicated in multiple homeostatic processes and is also known to have tumor-suppressor functions. There is a need for careful dosing of TGF-β drugs for therapeutic use and patient selection.

Elimination of Chlamydia muridarum from the female reproductive tract is IL-12p40 dependent, but independent of Th1 and Th2 cells

Chlamydia vaccine approaches aspire to induce Th1 cells for optimal protection, despite the fact that there is no direct evidence demonstrating Th1-mediated Chlamydia clearance from the female reproductive tract (FRT). We recently reported that T-bet-deficient mice can resolve primary Chlamydia infection normally, undermining the potentially protective role of Th1 cells in Chlamydia immunity. Here, we show that T-bet-deficient mice develop robust Th17 responses and that mice deficient in Th17 cells exhibit delayed bacterial clearance, demonstrating that Chlamydia-specific Th17 cells represent an underappreciated protective population. Additionally, Th2-deficient mice competently clear cervicovaginal infection. Furthermore, we show that sensing of IFN-γ by non-hematopoietic cells is essential for Chlamydia immunity, yet bacterial clearance in the FRT does not require IFN-γ secretion by CD4 T cells. Despite the fact that Th1 cells are not necessary for Chlamydia clearance, protective immunity to Chlamydia is still dependent on MHC class-II-restricted CD4 T cells and IL-12p40. Together, these data point to IL-12p40-dependent CD4 effector maturation as essential for Chlamydia immunity, and Th17 cells to a lesser extent, yet neither Th1 nor Th2 cell development is critical. Future Chlamydia vaccination efforts will be more effective if they focus on induction of this protective CD4 T cell population.

AIEC-dependent pathogenic Th17 cell transdifferentiation in Crohn's disease is suppressed by rfaP and ybaT deletion

Mucosal enrichment of the Adherent-Invasive E. coli (AIEC) pathotype and the expansion of pathogenic IFNγ-producing Th17 (pTh17) cells have been linked to Crohn's Disease (CD) pathogenesis. However, the molecular pathways underlying the AIEC-dependent pTh17 cell transdifferentiation in CD patients remain elusive. To this aim, we created and functionally screened a transposon AIEC mutant library of 10.058 mutants to identify the virulence determinants directly implicated in triggering IL-23 production and pTh17 cell generation. pTh17 cell transdifferentiation was assessed in functional assays by co-culturing AIEC-infected human dendritic cells (DCs) with autologous conventional Th17 (cTh17) cells isolated from blood of Healthy Donors (HD) or CD patients. AIEC triggered IL-23 hypersecretion and transdifferentiation of cTh17 into pTh17 cells selectively through the interaction with CD-derived DCs. Moreover, the chronic release of IL-23 by AIEC-colonized DCs required a continuous IL-23 neutralization to significantly reduce the AIEC-dependent pTh17 cell differentiation. The multi-step screenings of the AIEC mutant's library revealed that deletion of ybaT or rfaP efficiently hinder the IL-23 hypersecretion and hampered the AIEC-dependent skewing of protective cTh17 into pathogenic IFNγ-producing pTh17 cells. Overall, our findings indicate that ybaT (inner membrane transport protein) and rfaP (LPS-core heptose kinase) represent novel and attractive candidate targets to prevent chronic intestinal inflammation in CD.

Autophagy-mediated immune system regulation in reproductive system and pregnancy-associated complications

Autophagy lysosomal degradation is the main cell mechanism in cellular, tissue and organismal homeostasis and is controlled by autophagy-related genes (ATG). Autophagy has important effects in cellular physiology, including adaptation to metabolic stress, removal of dangerous cargo (such as protein aggregates, damaged organelles, and intracellular pathogens), regeneration during differentiation and development, and prevention of genomic damage in general. Also, it has been found that autophagy is essential for pre-implantation, development, and maintaining embryo survival in mammals. Under certain conditions, autophagy may be detrimental through pro-survival effects such as cancer progression or through possible cell death-promoting effects. Hormonal changes and environmental stress can initiate autophagy in reproductive physiology. The activity of autophagy can be upregulated under conditions like a lack of nutrients, inflammation, hypoxia, and infections. In this regard the dysregulation of autophagy involved in some pregnancy complications such as preeclampsia (PE) and pregnancy loss, and has a major impact on reproductive outcomes. Therefore, we aimed to discuss the relationship between autophagy and the female reproductive system, with a special focus on the immune system, and its role in fetal and maternal health.

The transcriptional regulator Sin3A balances IL-17A and Foxp3 expression in primary CD4 T cells

The Sin3 transcriptional regulator homolog A (Sin3A) is the core member of a multiprotein chromatin-modifying complex. Its inactivation at the CD4/CD8 double-negative stage halts further thymocyte development. Among various functions, Sin3A regulates STAT3 transcriptional activity, central to the differentiation of Th17 cells active in inflammatory disorders and opportunistic infections. To further investigate the consequences of conditional Sin3A inactivation in more mature precursors and post-thymic T cell, we have generated CD4-Cre and CD4-CreER^T2 Sin3A^F/F mice. Sin3A inactivation in vivo hinders both thymocyte development and peripheral T-cell survival. In vitro, in Th17 skewing conditions, Sin3A-deficient cells proliferate and acquire memory markers and yet fail to properly upregulate Il17a, Il23r, and Il22. Instead, IL-2⁺ and FOXP3⁺ are mostly enriched for, and their inhibition partially rescues IL-17A⁺ T cells. Notably, Sin3A deletion also causes an enrichment of genes implicated in the mTORC1 signaling pathway, overt STAT3 activation, and aberrant cytoplasmic RORγt accumulation. Thus, together our data unveil a previously unappreciated role for Sin3A in shaping critical signaling events central to the acquisition of immunoregulatory T-cell phenotypes.

Pathogenicity of Salmonella During Schistosoma-Salmonella Co-infections and the Importance of the Gut Microbiota

Antibiotic inefficacy in treating bacterial infections is largely studied in the context of developing resistance mechanisms. However, little attention has been paid to combined diseases mechanisms, interspecies pathogenesis and the resulting impact on antimicrobial treatment. This review will consider the co-infections of Salmonella and Schistosoma mansoni. It summarises the protective mechanisms that the pathophysiology of the two infections confer, which leads to an antibiotic protection phenomenon. This review will elucidate the functional characteristics of the gut microbiota in the context of these co-infections, the pathogenicity of these infections in infected mice, and the efficacy of the antibiotics used in treatment of these co-infections over time. Salmonella-Schistosoma interactions and the mechanism for antibiotic protection are not well established. However, antimicrobial drug inefficacy is an existing phenomenon in these co-infections. The treatment of schistosomiasis to ensure the efficacy of antibiotic therapy for bacterial infections should be considered in co-infected patients.

Genetic and Environmental Determinants of T Helper 17 Pathogenicity in Spondyloarthropathies

In Spondyloarthropathies (SpA), a common group of immune-mediated diseases characterised by excessive inflammation of musculo-skeletal structures and extra-articular organs, T helper 17 (Th17) cells are widely considered the main drivers of the disease. Th17 are able to modulate their genes according to the immune environment: upon differentiation, they can adopt either housekeeping, anti-bacterial gene modules or inflammatory, pathogenic functions, and only the latter would mediate immune diseases, such as SpA. Experimental work aimed at characterising Th17 heterogeneity is largely performed on murine cells, for which the in vitro conditions conferring pathogenic potential have been identified and replicated. Interestingly, Th17 recognising different microorganisms are able to acquire specific cytokine signatures. An emerging area of research associates this heterogeneity to the preferential metabolic needs of the cell. In summary, the tissue environment could be determinant for the acquisition of pathogenetic features; this is particularly important at barrier sites, such as the intestine, considered one of the key target organs in SpA, and likely a site of immunological changes that initiate the disease. In this review, we briefly summarise genetic, environmental and metabolic factors that could explain how homeostatic, anti-microbial Th17 could turn into disease-causing cells in Spondyloarthritis.

Prenatal maternal infection promotes tissue-specific immunity and inflammation in offspring

The immune system has evolved in the face of microbial exposure. How maternal infection experienced at distinct developmental stages shapes the offspring immune system remains poorly understood. Here, we show that during pregnancy, maternally restricted infection can have permanent and tissue-specific impacts on offspring immunity. Mechanistically, maternal interleukin-6 produced in response to infection can directly impose epigenetic changes on fetal intestinal epithelial stem cells, leading to long-lasting impacts on intestinal immune homeostasis. As a result, offspring of previously infected dams develop enhanced protective immunity to gut infection and increased inflammation in the context of colitis. Thus, maternal infection can be coopted by the fetus to promote long-term, tissue-specific fitness, a phenomenon that may come at the cost of predisposition to inflammatory disorders.

Functional analysis of two STAT1 gain-of-function mutations in two Iranian families with autosomal dominant chronic mucocutaneous candidiasis

Candidiasis is characterized by susceptibility to recurrent or persistent infections caused by Candida spp., typically Candida albicans, of cutaneous and mucosal surfaces. In this report, function and frequency of Th17 cells as well as genetics of patients susceptible to mucocutaneous candidiasis were studied. For patients, T-cell proliferation tests in response to Candida antigen, Th17 cell proportions, and STAT1 phosphorylation were evaluated through flow cytometry. Expression of IL17A, IL17F and IL22 genes were measured by real-time quantitative PCR. At the same time, whole exome sequencing was performed for all patients. We identified two heterozygous substitutions, one: c.821G > A (p. R274Q) was found in a multiplex family with three individuals affected, the second one: c.812A > C (p. Q271P) was found in a sporadic case. Both mutations are located in the coiled-coil domain (CCD) of STAT1. The frequency of Th17 cells, IL17A, IL17F, and IL22 gene expression in patients' peripheral blood mononuclear cells (PBMCs), and T-cell proliferation to Candida antigens were significantly reduced in the patients as compared to healthy controls. An increased STAT1 phosphorylation was observed in patients' PBMCs upon interferon (IFN)-γ stimulation as compared to healthy controls. We report two different but neighboring heterozygous mutations, located in exon 10 of the STAT1 gene, in four Iranian patients with CMC, one of whom also had hypothyroidism. These mutations were associated with impaired T cell proliferation to Candida antigen, low Th17 cell proportions, and increased STAT1 phosphorylation upon IFN-γ. We suggest that interfering with STAT1 phosphorylation might be a promising way for potential therapeutic measurements for such patients.

The determinant role of IL-6 in the establishment of inflammation leading to spontaneous preterm birth

Preterm birth (PTB) and its consequences are a major public health concern as preterm delivery is the main cause of mortality and morbidity at birth. There are many causes of PTB, but inflammation is undeniably associated with the process of premature childbirth and fetal injury. At present, treatments clinically available mostly involve attempt to arrest contractions (tocolytics) but do not directly address upstream maternal inflammation on development of the fetus. One of the possible solutions may lie in the modulation of inflammatory mediators. Of the many pro-inflammatory cytokines involved in the induction of PTB, IL-6 stands out for its pleiotropic effects and its involvement in both acute and chronic inflammation. Here, we provide a detailed review of the effects of IL-6 on the timing of childbirth, its occurrence during PTB and its indissociable roles with associated fetal tissue damage.

Noncanonical STAT3 activity sustains pathogenic Th17 proliferation and cytokine response to antigen

The STAT3 signaling pathway is required for early Th17 cell development, and therapies targeting this pathway are used for autoimmune disease. However, the role of STAT3 in maintaining inflammatory effector Th17 cell function has been unexplored. Th17ΔSTAT3 mice, which delete STAT3 in effector Th17 cells, were resistant to experimental autoimmune encephalomyelitis (EAE), a murine model of MS. Th17 cell numbers declined after STAT3 deletion, corresponding to reduced cell cycle. Th17ΔSTAT3 cells had increased IL-6-mediated phosphorylation of STAT1, known to have antiproliferative functions. Th17ΔSTAT3 cells also had reduced mitochondrial membrane potential, which can regulate intracellular Ca2+. Accordingly, Th17ΔSTAT3 cells had reduced production of proinflammatory cytokines when stimulated with myelin antigen but normal production of cytokines when TCR-induced Ca2+ flux was bypassed with ionomycin. Thus, early transcriptional roles of STAT3 in developing Th17 cells are later complimented by noncanonical STAT3 functions that sustain pathogenic Th17 cell proliferation and cytokine production.

T cell fate following Salmonella infection is determined by a STING-IRF1 signaling axis in mice

The innate immune response following infection with entero-invasive bacterial species is triggered upon release of cyclic di-guanylate monophosphate (c-di-GMP) into the host cell cytosol. Bacterial c-di-GMP activates the intracellular Sensor Stimulator of Interferon Genes (STING), encoded by Tmem173 in mice. Here we identify Interferon Regulatory Factor (IRF) 1 as a critical effector of STING-mediated microbial DNA sensing that is responsible for TH17 cell generation in the mucosal immune system. We find that STING activation induces IRF1-dependent transcriptional programs in dendritic cells (DCs) that define T cell fate determination, including induction of Gasdermin D, IL-1 family member cytokines, and enzymes for eicosanoid synthesis. Our results show that IRF1-dependent transcriptional programs in DCs are a prerequisite for antigen-specific TH17 subspecification in response to microbial c-di-GMP and Salmonella typhimurium infection. Our identification of a STING-IRF1 signaling axis for adaptive host defense control will aid further understanding of infectious disease mechanisms.

Environmental Exposures and Neuropsychiatric Disorders: What Role Does the Gut-Immune-Brain Axis Play?

PURPOSE OF REVIEW

Evidence is growing that environmental exposures-including xenobiotics as well as microbes-play a role in the pathogenesis of many neuropsychiatric disorders. Underlying mechanisms are likely to be complex, involving the developmentally sensitive interplay of genetic/epigenetic, detoxification, and immune factors. Here, we review evidence supporting a role for environmental factors and disrupted gut-immune-brain axis function in some neuropsychiatric conditions.

RECENT FINDINGS

Studies suggesting the involvement of an altered microbiome in triggering CNS-directed autoimmunity and neuropsychiatric disturbances are presented as an intriguing example of the varied mechanisms by which environmentally induced gut-immune-brain axis dysfunction may contribute to adverse brain outcomes. The gut-immune-brain axis is a burgeoning frontier for investigation of neuropsychiatric illness. Future translational research to define individual responses to exogenous exposures in terms of microbiome-dependent skew of the metabolome, immunity, and brain function may serve as a lens for illumination of pathways involved in the development of CNS disease and fuel discovery of novel interventions.

Diversity in the T cell response to Chlamydia-sum are better than one

Chlamydia trachomatis is responsible for an increasing number of sexually transmitted infections in the United States and is a common cause of serious pathology in the female reproductive tract (FRT). Given the impact and incidence of these infections, the production of an effective Chlamydia vaccine is a public health priority. Mouse models of Chlamydia infection have been utilized to develop a detailed and mechanistic understanding of protective immunity in the FRT. These studies reveal that MHC class-II restricted Chlamydia-specific CD4 T cells are critical for primary bacterial clearance and provide effective protection against secondary infection in the FRT. Despite the clear importance of IFN- γ produced by CD4 Th1 cells, there are also suggestions of wider functional heterogeneity in the CD4 T cell response to Chlamydia infection. Understanding the role of this diversity in the CD4 T helper cell response in the FRT should allow a more nuanced view of CD4 T cell biology in the context of Chlamydia infection and may be critical for vaccine development. Here, we summarize our current understanding of CD4 T helper subsets in the clearance of Chlamydia and discuss some areas where knowledge needs to be further extended by additional experimentation.

Neonatal neutrophils stimulated by group B Streptococcus induce a proinflammatory T-helper cell bias

BackgroundGroup B Streptococcus (GBS) infection causes inflammatory comorbidities in newborns. While the mechanisms remain unclear, evidence suggests that impaired innate-adaptive immune interactions may be contributory. We hypothesized that GBS-stimulated neonatal neutrophils provide a milieu that may drive proinflammatory T-helper (Th) cell programming.MethodsNeutrophils were stimulated with Type III GBS (COH1); supernatants or intact neutrophils were cocultured with CD4⁺ T cells or regulatory T cells (Tregs). Resulting intracellular cytokines and nuclear transcription factors were determined by multicolor flow cytometry.ResultsGBS-stimulated neutrophils released soluble mediators that induced greater interleukin-17 (IL-17) responses in neonatal vs. adult CD4⁺ T cells in the absence of added polarizing cytokines. GBS-stimulated neonatal neutrophils also induced robust expression of the canonical nuclear transcription factors for Th1 (Tbet) and Th17 (IL-17) cells in CD4⁺ T cells. Following GBS stimulation, both intact neutrophils and neutrophil-derived mediators promoted the generation of Tregs with Th1 and Th17 characteristics.ConclusionGBS-stimulated neonatal neutrophils bias the in vitro Th differentiation program of neonatal CD4⁺ T cells and promote proinflammatory Th1 and Th17 phenotypes in Tregs. Our data suggest that developmental modifications of innate-adaptive immune cross-talk mechanisms may contribute to the inflammatory complications associated with neonatal GBS infection.

Discoidin domain receptor 1 promotes Th17 cell migration by activating the RhoA/ROCK/MAPK/ERK signaling pathway

Effector T cell migration through the tissue extracellular matrix (ECM) is an important step of the adaptive immune response and in the development of inflammatory diseases. However, the mechanisms involved in this process are still poorly understood. In this study, we addressed the role of a collagen receptor, the discoidin domain receptor 1 (DDR1), in the migration of Th17 cells. We showed that the vast majority of human Th17 cells express DDR1 and that silencing DDR1 or using the blocking recombinant receptor DDR1:Fc significantly reduced their motility and invasion in three-dimensional (3D) collagen. DDR1 promoted Th17 migration by activating RhoA/ROCK and MAPK/ERK signaling pathways. Interestingly, the RhoA/ROCK signaling module was required for MAPK/ERK activation. Finally, we showed that DDR1 is important for the recruitment of Th17 cells into the mouse dorsal air pouch containing the chemoattractant CCL20. Collectively, our results indicate that DDR1, via the activation of RhoA/ROCK/MAPK/ERK signaling axis, is a key pathway of effector T cell migration through collagen of perivascular tissues. As such, DDR1 can contribute to the development of Th17-dependent inflammatory diseases.

Salmonella Typhimurium, the major causative agent of foodborne illness inactivated by a phage lysis system provides effective protection against lethal challenge by induction of robust cell-mediated immune responses and activation of dendritic cells

Salmonella Typhimurium infection via foodborne transmission remains a major public health threat even in developed countries. Vaccines have been developed to reduce the disease burden at the pre-harvest stage, but the cell-mediated immune response against intracellular invasion of the pathogen is not sufficiently elicited by conventional killed Salmonella vaccines, which are safer than live vaccines. In this study, we developed a genetically inactivated vaccine candidate by introducing lysis plasmid pJHL454 harboring the λ phage holin-endolysin system into S. Typhimurium; we designated this vaccine JOL1950. In vitro expression of endolysin was validated by immunoblotting, and complete inactivation of JOL1950 cells was observed following 36 h of the lysis. Electron microscopic examinations by scanning electron microscopy and immunogold labeling transmission EM revealed conserved surface antigenic traits of the JOL1950 cells after lysis. An in vivo immunogenicity study in mice immunized with lysed cells showed significantly increased serum IgG, IgG1, and IgG2a levels. Further, we observed markedly increased in vitro cell proliferation and upregulation of Th1, Th2, and Th17 cytokines in the repulsed splenic T-cells of immunized mice. In dendritic cells (DCs) treated with lysed JOL1950, we observed a significant increase in dendritic cell activation, co-stimulatory molecule production, and levels of immunomodulatory cytokines. In addition, Th1 and Th17 cytokines were also released by naïve CD4⁺ T-cells pulsed with primed DCs. Lysed JOL1950 also protected against lethal challenge in immunized mice. Together, these results indicate that our vaccine candidate has great potential to induce cell-mediated immunity against S. Typhimurium by facilitating the activation of DCs.

Activation of iNKT Cells Prevents Salmonella-Enterocolitis and Salmonella-Induced Reactive Arthritis by Downregulating IL-17-Producing γδT Cells

Reactive arthritis (ReA) is an inflammatory condition of the joints that arises following an infection. Salmonella enterocolitis is one of the most common infections leading to ReA. Although the pathogenesis remains unclear, it is known that IL-17 plays a pivotal role in the development of ReA. IL-17-producers cells are mainly Th17, iNKT, and γδT lymphocytes. It is known that iNKT cells regulate the development of Th17 lineage. Whether iNKT cells also regulate γδT lymphocytes differentiation is unknown. We found that iNKT cells play a protective role in ReA. BALB/c Jα18^−/− mice suffered a severe Salmonella enterocolitis, a 3.5-fold increase in IL-17 expression and aggravated inflammation of the synovial membrane. On the other hand, activation of iNKT cells with α-GalCer abrogated IL-17 response to Salmonella enterocolitis and prevented intestinal and joint tissue damage. Moreover, the anti-inflammatory effect of α-GalCer was related to a drop in the proportion of IL-17-producing γδT lymphocytes (IL17-γδTcells) rather than to a decrease in Th17 cells. In summary, we here show that iNKT cells play a protective role against Salmonella-enterocolitis and Salmonella-induced ReA by downregulating IL17-γδTcells.

Simultaneous Subcutaneous and Intranasal Administration of a CAF01-Adjuvanted Chlamydia Vaccine Elicits Elevated IgA and Protective Th1/Th17 Responses in the Genital Tract

The selection of any specific immunization route is critical when defining future vaccine strategies against a genital infection like Chlamydia trachomatis (C.t.). An optimal Chlamydia vaccine needs to elicit mucosal immunity comprising both neutralizing IgA/IgG antibodies and strong Th1/Th17 responses. A strategic tool to modulate this immune profile and mucosal localization of vaccine responses is to combine parenteral and mucosal immunizations routes. In this study, we investigate whether this strategy can be adapted into a two-visit strategy by simultaneous subcutaneous (SC) and nasal immunization. Using a subunit vaccine composed of C.t. antigens (Ags) adjuvanted with CAF01, a Th1/Th17 promoting adjuvant, we comparatively evaluated Ag-specific B and T cell responses and efficacy in mice following SC and simultaneous SC and nasal immunization (SIM). We found similar peripheral responses with regard to interferon gamma and IL-17 producing Ag-specific splenocytes and IgG serum levels in both vaccine strategies but in addition, the SIM protocol also led to Ag-specific IgA responses and increased B and CD4⁺ T cells in the lung parenchyma, and in lower numbers also in the genital tract (GT). Following vaginal infection with C.t., we observed that SIM immunization gave rise to an early IgA response and IgA-secreting plasma cells in the GT in contrast to SC immunization, but we were not able to detect more rapid recruitment of mucosal T cells. Interestingly, although SIM vaccination in general improved mucosal immunity we observed no improved efficacy against genital infection compared to SC, a finding that warrants for further investigation. In conclusion, we demonstrate a novel vaccination strategy that combines systemic and mucosal immunity in a two-visit strategy.

Augmented Th17-type immune responses in preterm neonates exposed to histologic chorioamnionitis

BACKGROUND

Histologic chorioamnionitis (HCA) is a placental inflammatory disorder that frequently precedes preterm delivery. HCA increases risk for long-standing inflammatory injury and may influence immune programming, particularly in preterm (PT) neonates. We hypothesized that HCA exposure is associated with an increased circulating frequency of proinflammatory, Th17-type responses.

METHODS

Placental cord blood was collected from HCA-exposed or control neonates (23-41 wk gestation). Frequencies of Th17 and T regulatory (Treg) cells and assessments of Th17-type features in CD4 and Treg cells were determined by flow cytometric analysis.

RESULTS

Cord blood samples from 31 PT and 17 term neonates were analyzed by flow cytometry. A diagnosis of HCA in extremely PT (EPT, GA ≤ 30 wk) gestations was associated with the highest cord blood frequencies of progenitor (pTh17, CD4⁺CD161⁺) and mature (mTh17, CD4⁺CD161⁺CCR6⁺) Th17 cells. Preterm neonates exposed to HCA also exhibited elevated cord blood frequencies of IL-17⁺ Treg cells, as well as T cells with effector memory phenotype (TEM) that coexpressed Th17-type surface antigens.

CONCLUSION

Th17-type responses are amplified in preterm neonates exposed to HCA. We speculate that a Th17 bias may potentiate the inflammatory responses and related morbidity observed in preterm neonates whose immune systems have been "primed" by HCA exposure.

BATF2 inhibits immunopathological Th17 responses by suppressing Il23a expression during Trypanosoma cruzi infection

Inappropriate IL-17 responses are implicated in chronic tissue inflammation. IL-23 contributes to Trypanosoma cruzi-specific IL-17 production, but the molecular mechanisms underlying regulation of the IL-23-IL-17 axis during T. cruzi infection are poorly understood. Here, we demonstrate a novel function of BATF2 as a negative regulator of Il23a in innate immune cells. IL-17, but not IFN-γ, was more highly produced by CD4⁺ T cells from spleens and livers of T. cruzi-infected Batf2^-/- mice than by those of wild-type mice. In this context, Batf2^-/- mice showed severe multiorgan pathology despite reduced parasite burden. T. cruzi-induced IL-23 production was increased in Batf2^-/- innate immune cells. The T. cruzi-induced enhanced Th17 response was abrogated in Batf2^-/-Il23a^-/- mice. The interaction of BATF2 with c-JUN prevented c-JUN-ATF-2 complex formation, inhibiting Il23a expression. These results demonstrate that IFN-γ-inducible BATF2 in innate immune cells controls Th17-mediated immunopathology by suppressing IL-23 production during T. cruzi infection.

CD73 is expressed by inflammatory Th17 cells in experimental autoimmune encephalomyelitis but does not limit differentiation or pathogenesis

CD73 works together with CD39 to convert extracellular ATP to immunoregulatory adenosine, thus inhibiting inflammation. TGFβ-mediated CD73 expression on 'regulatory' Th17 cells limits their ability to eradicate tumors, similar to the immunosuppressive mechanism described for CD73 on Tregs. However, CD73 is also expressed on Th17 cells thought to be inflammatory in Crohn's disease. CD73 has previously been reported to contribute to inflammation in the central nervous system (CNS). In experimental autoimmune encephalomyelitis (EAE), we found that inflammatory cytokine-producing Th17 cells showed increased CD73 expression as disease progressed. We therefore hypothesized that CD73 could be important for limiting the expansion or pathogenic function of Th17 cells in autoimmune inflammation of the CNS. Surprisingly, EAE development was not enhanced or inhibited by CD73 deficiency; there was correspondingly no difference in induction of Th17-associated cytokines IL-17, IFNγ or GM-CSF or recruitment of either inflammatory or regulatory cells to the central nervous system. We confirmed that CD73 was similarly not required for differentiation of Th17 cells in vitro. These data show that while CD73 expression is regulated during EAE, this enzyme is not absolutely required to either promote or limit Th17 cell expansion or EAE severity.

Cardiovascular and Metabolic Diseases Comorbid with Psoriasis: Beyond the Skin

A close association of systemic inflammation with cardiovascular diseases and metabolic syndrome is recently a popular topic in medicine. Psoriasis is a chronic inflammatory skin disease with a prevalence of approximately 0.1-0.5% in Asians. It is characterized by widespread scaly erythematous macules that cause significant physical and psychological burdens for the affected individuals. The accelerated inflammation driven by the TNF-α/IL-23/IL-17A axis is now known to be the major mechanism in the development of psoriasis. Psoriasis is not a mere skin disease; it is significantly associated with cardiovascular diseases and metabolic syndrome, which suggests that the chronic skin inflammation extends the systemic inflammation beyond the skin. In this article, we review the epidemiological and pathological aspects of psoriasis and its comorbidities.

Are Th17 Cells Playing a Role in Immunity to Dermatophytosis?

Despite their superficial localization in the skin, pathogenic dermatophytes can induce a complex but still misunderstood immune response in their hosts. The cell-mediated immunity (CMI) is correlated with both clinical recovery and protection against reinfection, and CD4+ T lymphocytes have been recognized as a crucial component of the immune defense against dermatophytes. Before the discovery of the Th17 pathway, CMI was considered to be only dependent of Th1 cells, and thus most studies on the immunology of dermatophytosis have focused on the Th1 pathway. Nevertheless, the fine comparative analysis of available scientific data on immunology of dermatophytosis in one hand and on the Th17 pathway mechanisms involved in opportunistic mucosal fungal infections in the other hand reveals that some key elements of the Th17 pathway can be activated by dermatophytes. Stimulation of the Th17 pathway could occur through the activation of some C-type lectin-like receptors and inflammasome in antigen-presenting cells. The Th17 cells could go back to the affected skin and by the production of signature cytokines could induce the effector mechanisms like the recruitment of polymorphonuclear neutrophils and the synthesis of antimicrobial peptides. In conclusion, besides the Th1 pathway, which is important to the immune response against dermatophytes, there are also growing evidences for the involvement of the Th17 pathway.

Upregulation of duck interleukin-17A during Riemerella anatipestifer infection

Although IL-17 cytokines play critical roles in host defense immunity, dysregulated expression of these cytokines is associated with inflammation and autoimmune diseases. Riemerella anatipestifer is the most important infectious bacterium in the duck industry. Interestingly, not all avian species are equally susceptible to R. anatipestifer infection. This paper reports the first description of mortality rate, bacterial burden, and expression profiles of immune-related genes between ducks and chickens infected with R. anatipestifer. Ducks exhibited increased susceptibility to R. anatipestifer infection compared to chickens, as determined by mortality rate and bacterial burden. Comparative expression analyses of immune-related genes in R. anatipestifer-infected tissues obtained from both species revealed that TLR3, TLR7, IL-2, IL-4, and IFN-γ transcript levels were higher in chickens, whereas TLR4 and IL-17A transcript levels were higher in ducks. Marked increases in expression of IL-17A and IL-6, but not TGF-β, were associated with Th17 cell differentiation in duck splenic lymphocytes, but not in chicken splenic lymphocytes, stimulated with R. anatipestifer. Moreover, upregulation of IL-1β, IL-6, and IL-17A mRNA expressions, but not TGF-β, was confirmed in the liver and spleen of ducks infected with R. anatipestifer, indicating that IL-17A is strongly associated with Riemerella infection in ducks.

Cross-reactive multifunctional CD4+ T cell responses against Salmonella enterica serovars Typhi, Paratyphi A and Paratyphi B in humans following immunization with live oral typhoid vaccine Ty21a

The live oral typhoid vaccine Ty21a elicits predominantly CD8+, as well as CD4+ T cells mediated immune responses. Clinical field studies showed that Ty21a is moderately effective against S. Typhi and S. Paratyphi B, but not S. Paratyphi A infections. In this study we describe the in depth characterization of S. Typhi, S. Paratyphi A and S. Paratyphi B cross-reactive CD4+ T cell responses elicited following immunization with Ty21a. PBMC samples were collected from 16 healthy volunteers before and 42/84days after Ty21a immunization and stimulated ex-vivo with Salmonella-infected targets. Multiparametric flow cytometry was used to detect the vaccine elicited Salmonella-specific responses in T effector/memory (T_EM) and CD45RA+ T effector/memory (T_EMRA) CD4+ cell subsets, by measuring CD4+ multifunctional (MF) cells that concomitantly produced IFN-γ, TNF-α, IL-2, MIP-1β, IL-17A and/or expressed CD107a. Post-vaccination increases in S. Typhi-specific MF cells were observed in CD4+ T_EM and T_EMRA subsets which predominantly produced IFN-γ and/or TNF-α, while IL-2 was produced by a smaller cell subset. A small proportion of those MF cells also produced MIP-1β, IL-17A and expressed CD107a (a marker associated with cytotoxicity). Approximately one third of these specific MF cells have the potential to migrate to the gut mucosa, as evidenced by co-expression of the gut-homing molecule integrin α₄β₇. In contrast to our previous observations with CD8+ T cells, MF CD4+ T cell responses to the different Salmonella serovars evaluated were similar in magnitude and characteristics. We conclude that although induction of cross-reactive CD4+ MF effector T cells suggest a possible role in Salmonella-immunity, these responses are unlikely to provide an immunological basis for the observed efficacy of Ty21a against S. Typhi and S. Paratyphi B, but not to S. Paratyphi A.

Overview of cytokines and nitric oxide involvement in immuno-pathogenesis of inflammatory bowel diseases

Inflammatory bowel diseases (IBDs), including Crohn’s disease and ulcerative colitis are complex disorders with undetermined etiology. Several hypotheses suggest that IBDs result from an abnormal immune response against endogenous flora and luminal antigens in genetically susceptible individuals. The dysfunction of the mucosal immune response is implicated in the pathogenesis of IBD. The balance between pro-inflammatory cytokines [tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-8, and IL-17A], anti-inflammatory cytokines (IL-4 and IL-13), and immunoregulatory cytokines (IL-10 and transforming growth factors β) is disturbed. Moreover, evidence from animal and clinical studies demonstrate a positive correlation between an increased concentration of nitric oxide (NO) and the severity of the disease. Interestingly, proinflammatory cytokines are involved in the up-regulation of inducible oxide synthase (iNOS) expression in IBD. However, anti-inflammatory and immunoregulatory cytokines are responsible for the negative regulation of iNOS. A positive correlation between NO production and increased pro-inflammatory cytokine levels (TNF-α, IL-6, IL-17, IL-12, and interferon-γ) were reported in patients with IBD. This review focuses on the role of cytokines in intestinal inflammation and their relationship with NO in IBD.

The Role of Interleukin-23 in the Early Development of Emphysema in HIV1(+) Smokers

Rationale. Matrix metalloproteinase-9 (MMP-9) expression is upregulated in alveolar macrophages (AM) of HIV1⁺ smokers who develop emphysema. Knowing that lung epithelial lining fluid (ELF) of HIV1⁺ smokers contains increased levels of inflammatory cytokines compared to HIV1⁻ smokers, we hypothesized that upregulation of lung cytokines in HIV1⁺ smokers may be functionally related to increased MMP-9 expression. Methods. Cytokine arrays evaluated cytokine protein levels in ELF obtained from 5 groups of individuals: HIV1⁻ healthy nonsmokers, HIV1⁻ healthy smokers, HIV1⁻ smokers with low diffusing capacity (DL_CO), HIV1⁺ nonsmokers, and HIV1⁺ smokers with low DL_CO. Results. Increased levels of the Th17 related cytokine IL-23 were found in HIV1⁻ smokers with low DL_CO and HIV1⁺ smokers and nonsmokers. Relative IL-23 gene expression was increased in AM of HIV1⁺ individuals, with greater expression in AM of HIV1⁺ smokers with low DL_CO. Infection with HIV1 in vitro induced IL-23 expression in normal AM. IL-23 stimulation of AM/lymphocyte cocultures in vitro induced upregulation of MMP-9. Lung T lymphocytes express receptor IL-23R and interact with AM in order to upregulate MMP-9. Conclusion. This mechanism may contribute to the increased tissue destruction in the lungs of HIV1⁺ smokers and suggests that Th17 related inflammation may play a role.

Mechanisms of Cholera Toxin in the Modulation of TH17 Responses

Numerous studies have shown that TH17 cells and their signature cytokine IL-17A are critical to host defense against various bacterial and fungal infections. The protective responses mediated by TH17 cells and IL-17A include the recruitment of neutrophils, release of antimicrobial peptides and chemokines, and enhanced tight junction of epithelial cells. Due to the importance of TH17 cells in infections, efforts have been made to develop TH17-based vaccines. The goal of vaccination is to establish a protective immunological memory. Most currently approved vaccines are antibody-based and have limited protection against stereotypically different strains. Studies show that T-cell-based vaccines may overcome this limitation and protect hosts against infection of different strains. Two main strategies are used to develop TH17 vaccines: identification of TH17-specific antigens and TH17-skewing adjuvants. Studies have revealed that cholera toxin (CT) induces a potent Th17 response following vaccination. Antigen vaccination along with CT induces a robust TH17 response, which is sometimes accompanied by TH1 responses. Due to the toxicity of CT, it is hard to apply CT in a clinical setting. Thus, understanding how CT modulates TH17 responses may lead to the development of successful TH17-based vaccines.

Th1 and Th17 Cells in Tuberculosis: Protection, Pathology, and Biomarkers

The outcome of Mycobacterium tuberculosis (Mtb) infection ranges from a complete pathogen clearance through asymptomatic latent infection (LTBI) to active tuberculosis (TB) disease. It is now understood that LTBI and active TB represent a continuous spectrum of states with different degrees of pathogen “activity,” host pathology, and immune reactivity. Therefore, it is important to differentiate LTBI and active TB and identify active TB stages. CD4⁺ T cells play critical role during Mtb infection by mediating protection, contributing to inflammation, and regulating immune response. Th1 and Th17 cells are the main effector CD4⁺ T cells during TB. Th1 cells have been shown to contribute to TB protection by secreting IFN-γ and activating antimycobacterial action in macrophages. Th17 induce neutrophilic inflammation, mediate tissue damage, and thus have been implicated in TB pathology. In recent years new findings have accumulated that alter our view on the role of Th1 and Th17 cells during Mtb infection. This review discusses these new results and how they can be implemented for TB diagnosis and monitoring.

TIR Domain-Containing Adapter-Inducing Beta Interferon (TRIF) Mediates Immunological Memory against Bacterial Pathogens

Induction of adaptive immunity leads to the establishment of immunological memory; however, how innate immunity regulates memory T cell function remains obscure. Here we show a previously undefined mechanism in which innate and adaptive immunity are linked by TIR domain-containing adapter-inducing beta interferon (TRIF) during establishment and reactivation of memory T cells against Gram-negative enteropathogens. Absence of TRIF in macrophages (Mϕs) but not dendritic cells led to a predominant generation of CD4(+) central memory T cells that express IL-17 during enteric bacterial infection in mice. TRIF-dependent type I interferon (IFN) signaling in T cells was essential to Th1 lineage differentiation and reactivation of memory T cells. TRIF activated memory T cells to facilitate local neutrophil influx and enhance bacterial elimination. These results highlight the importance of TRIF as a mediator of the innate and adaptive immune interactions in achieving the protective properties of memory immunity against Gram-negative bacteria and suggest TRIF as a potential therapeutic target.

Optimal clearance of Sporothrix schenckii requires an intact Th17 response in a mouse model of systemic infection

The discovery of Th17 cells, along with many other Th cell subsets in the recent years, has expanded the Th1/Th2 paradigm that had persisted since its proposition by Mosmann in 1986. Defined by the characteristic expression of the transcription factor retinoic-related orphan receptor γt (RORγt) and production of IL-17A (IL-17), Th17 cells are powerful inducers of tissue inflammation with a recognized role against extracellular bacteria and fungi. Despite this, the interest in their study came from the pivotal role they play in the development and maintenance of major chronic inflammatory conditions such as multiple sclerosis, rheumatoid arthritis and Crohn's disease, hence they have been the target of promising new anti-Th17 therapies. Accordingly, the identification of opportunistic pathogens whose clearance relies on the Th17 response is of huge prophylactic importance. As shown here for the first time, this applies to Sporothrix schenckii, a thermo-dimorphic fungus and the causative agent of sporotrichosis. Our results show that both Th17 and Th1/Th17 mixed cells are developed during the S. schenckii systemic mice infection, which also leads to augmented production of IL-17 and IL-22. Also, by using an antibody-mediated IL-23 depletion model, we further demonstrate that optimal fungal clearance, but not survival, depends on an intact Th17 response.

Breast-fed and bottle-fed infant rhesus macaques develop distinct gut microbiotas and immune systems

Diet has a strong influence on the intestinal microbiota in both humans and animal models. It is well established that microbial colonization is required for normal development of the immune system and that specific microbial constituents prompt the differentiation or expansion of certain immune cell subsets. Nonetheless, it has been unclear how profoundly diet might shape the primate immune system or how durable the influence might be. We show that breast-fed and bottle-fed infant rhesus macaques develop markedly different immune systems, which remain different 6 months after weaning when the animals begin receiving identical diets. In particular, breast-fed infants develop robust populations of memory T cells as well as T helper 17 (TH17) cells within the memory pool, whereas bottle-fed infants do not. These findings may partly explain the variation in human susceptibility to conditions with an immune basis, as well as the variable protection against certain infectious diseases.

Aggregatibacter actinomycetemcomitans induces Th17 cells in atherosclerotic lesions

Th17 cells have been linked to the pathogenesis of several chronic inflammatory and autoimmune diseases. However, the role of Th17 cells and IL-17 in atherosclerosis remains poorly understood. We previously reported that Aggregatibacter actinomycetemcomitans (Aa) bacteremia accelerated atherosclerosis accompanied by inflammation in apolipoprotein E-deficient spontaneously hyperlipidemic (Apoe(shl)) mice. In this study, we investigated whether Aa promotes the Th17 inducing pathway in Aa-challenged Apoe(shl) mice. Mice were intravenously injected with live Aa HK1651 or vehicles. Time-course analysis of splenic IL-17(+)CD4(+) cell frequencies, the proximal aorta lesion area, serum IL-17, IL-6, TGF-β and IL-1β levels, the mRNA expression of Th17-related molecules such as IL-1β, IL-6, IL17RA, STAT3, IL-21, IL-23, TGF-β and RORγt, Th17-related microRNA levels and the levels of AIM-2, Mincle and NLRP3 were examined. Challenge with Aa time dependently induced tropism of Th17 cells in the spleen and increase in atheromatous lesions in the aortic sinus of Apoe(shl) mice. Serum IL-17, IL-6, TGF-β and IL-1β levels were significantly enhanced by Aa. The gene expression of IL-1β, IL-6, IL-17RA, IL-21, IL-23, TGF-β, STAT3, RORγt, AIM-2, Mincle and NLRP3 was also time dependently stimulated in the aorta of Aa-challenged mice. Furthermore, Aa challenge significantly increased the expression of miR-146b and miR-155 in the aorta. Based on the results, it seems that Aa stimulates Th17 induction that affects the progression of Aa-accelerated atherosclerosis.

IL-17A-mediated protection against Acanthamoeba keratitis

Acanthamoeba keratitis (AK) is a very painful and vision-impairing infection of the cornea that is difficult to treat. Although past studies have indicated a critical role of neutrophils and macrophages in AK, the relative contribution of the proinflammatory cytokine, IL-17A, that is essential for migration, activation, and function of these cells into the cornea is poorly defined. Moreover, the role of the adaptive immune response, particularly the contribution of CD4(+) T cell subsets, Th17 and regulatory T cells , in AK is yet to be understood. In this report, using a mouse corneal intrastromal injection-induced AK model, we show that Acanthamoeba infection induces a strong CD4(+) T effector and regulatory T cell response in the cornea and local draining lymph nodes. We also demonstrate that corneal Acanthamoeba infection induces IL-17A expression and that IL-17A is critical for host protection against severe AK pathology. Accordingly, IL-17A neutralization in Acanthamoeba-infected wild-type mice or Acanthamoeba infection of mice lacking IL-17A resulted in a significantly increased corneal AK pathology, increased migration of inflammatory cells at the site of inflammation, and a significant increase in the effector CD4(+) T cell response in draining lymph nodes. Thus, in sharp contrast with other corneal infections such as herpes and Pseudomonas aeruginosa keratitis where IL-17A exacerbates corneal pathology and inflammation, the findings presented in this article suggest that IL-17A production after Acanthamoeba infection plays an important role in host protection against invading parasites.

Schizophrenia and the gut-brain axis

Several risk factors for the development of schizophrenia can be linked through a common pathway in the intestinal tract. It is now increasingly recognized that bidirectional communication exists between the brain and the gut that uses neural, hormonal, and immunological routes. An increased incidence of gastrointestinal (GI) barrier dysfunction, food antigen sensitivity, inflammation, and the metabolic syndrome is seen in schizophrenia. These findings may be influenced by the composition of the gut microbiota. A significant subgroup of patients may benefit from the initiation of a gluten and casein-free diet. Antimicrobials and probiotics have therapeutic potential for reducing the metabolic dysfunction and immune dysregulation seen in patients with schizophrenia.

Development and survival of Th17 cells within the intestines: the influence of microbiome- and diet-derived signals

Th17 cells have emerged as important mediators of host defense and homeostasis at barrier sites, particularly the intestines, where the greatest number and diversity of the microbiota reside. A critical balance exists between protection of the host from its own microbiota and pathogens and the development of immune-mediated disease. Breaches of local innate immune defenses provide critical stimuli for the induction of Th17 cell development, and additional cues within these tissues promote Th17 cell survival and/or plasticity. Normally, this results in eradication of the microbial threat and restitution of homeostasis. When dysregulated, however, Th17 cells can cause a range of immune-mediated diseases, whether directed against Ags derived from the microbiota, such as in inflammatory bowel disease, or against self-Ags in a range of autoimmune diseases. This review highlights recent discoveries that provide new insights into ways in which environmental signals impact Th17 cell development and function in the intestines.

Augmentation of lymphocytes activation and T cell modulation by the extracts from some Euphorbia species

CONTEXT

Euphorbia is an important Euphorbiaceae genus that is traditionally being used for various infections, inflammation, and cancer.

OBJECTIVE

The present study investigated the possible in vitro immunomodulatory effect of three species of Euphorbia genus including Euphorbia microciadia Boiss, Euphorbia osyridea Boiss, and Euphorbia heteradenia Jaub. & Sp. on lymphocyte activation and cytokine secretion.

MATERIALS AND METHODS

Human lymphocytes were cultured in the presence of various concentrations (0.1-200 µg/ml) of the butanol/hexane extracts of the plants in the presence or absence of phytohemmagglutinin (PHA). The activation of lymphocytes after 48 h was determined by a proliferation assay. The release of T cell cytokines was studied to determine the dominant T cell subsets involved in the immune response.

RESULTS

All three plant extracts increased the proliferation of PHA-treated lymphocytes (maximum; 132% of control). Extract treatment of lymphocytes in the absence of PHA resulted in an increased proliferation of the cells indicating their lymphocyte mitogenic activity (maximum at 10 µg/ml E. microciadia extract; 494.5 ± 42.2% of control, p < 0.01). The extracts of E. microciadia and E. osyridea could increase IL-4 and IL-10 secretion but not IFN-γ production showing their capacity to deviate immune response toward a Th2 pattern. Euphorbia heteradenia did not change the release of IL-4 and IFN-γ cytokines but increased IL-10 production. The three extracts stimulated lymphocytes to produce IL-17 which showed their possible effects on Th17 cells activation.

CONCLUSION

The studied extracts had the ability to modulate T cell responses suggesting their possible beneficial effects on immune host defense.

Defective IL-17- and IL-22-dependent mucosal host response to Candida albicans determines susceptibility to oral candidiasis in mice expressing the HIV-1 transgene

BACKGROUND

The tissue-signaling cytokines IL-17 and IL-22 are critical to host defense against oral Candida albicans infection, by their induction of oral antimicrobial peptide expression and recruitment of neutrophils. Mucosal Th17 cells which produce these cytokines are preferentially depleted in HIV-infected patients. Here, we tested the hypothesis that defective IL-17- and IL-22-dependent host responses to C. albicans determine the phenotype of susceptibility to oropharyngeal candidiasis (OPC) in transgenic (Tg) mice expressing HIV-1.

RESULTS

Naïve CD4+ T-cells and the differentiated Th1, Th2, Th17, Th1Th17 and Treg lineages were all profoundly depleted in cervical lymph nodes (CLNs) of these Tg mice. However, naive CD4+ cells from Tg mice maintained the capacity to differentiate into these lineages in response to polarizing cytokines in vitro. Expression of Il17, Il22, S100a8 and Ccl20 was enhanced in oral mucosal tissue of non-Tg, but not of Tg mice, after oral infection with C. albicans. Treatment of infected Tg mice with the combination of IL-17 and IL-22, but not IL-17 or Il-22 alone, significantly reduced oral burdens of C. albicans and abundance of Candida hyphae in the epithelium of tongues of infected Tg mice, and restored the ability of the Tg mice to up-regulate expression of S100a8 and Ccl20 in response to C. albicans infection.

CONCLUSIONS

These findings demonstrate that defective IL-17- and IL-22-dependent induction of innate mucosal immunity to C. albicans is central to the phenotype of susceptibility to OPC in these HIV transgenic mice.

Salmonella enterica in the Chicken: How it has Helped Our Understanding of Immunology in a Non-Biomedical Model Species

Salmonella infection of the chicken is important both as a source of foodborne human salmonellosis and as a source of disease in the chicken itself. Vaccination and other control strategies require an understanding of the immune response and as such have been important in understanding both mucosal immunity and more generally the response to bacterial infection. In this review, we discuss the contribution the study of avian salmonellosis has made to understanding innate immunity including the function of phagocytic cells, pattern recognition receptors, and defensins. The mucosal response to Salmonella infection and its regulation and the contribution this makes in protection against infection and persistence within the gut and future directions in better understanding the role of TH17 and Tregs in this response. Finally, we discuss the role of the immune system and its modulation in persistent infection and infection of the reproductive tract. We also outline key areas of research required to fully understand the interaction between the chicken immune system and Salmonella and how infection is maintained in the absence of substantive gastrointestinal disease.

Inflammation and vitamin D: the infection connection

INTRODUCTION

Inflammation is believed to be a contributing factor to many chronic diseases. The influence of vitamin D deficiency on inflammation is being explored but studies have not demonstrated a causative effect.

METHODS

Low serum 25(OH)D is also found in healthy persons exposed to adequate sunlight. Despite increased vitamin D supplementation inflammatory diseases are increasing. The current method of determining vitamin D status may be at fault. The level of 25(OH)D does not always reflect the level of 1,25(OH)2D. Assessment of both metabolites often reveals elevated 1,25(OH)2D, indicating abnormal vitamin D endocrine function.

FINDINGS

This article reviews vitamin D's influence on the immune system, examines the myths regarding vitamin D photosynthesis, discusses ways to accurately assess vitamin D status, describes the risks of supplementation, explains the effect of persistent infection on vitamin D metabolism and presents a novel immunotherapy which provides evidence of an infection connection to inflammation.

CONCLUSION

Some authorities now believe that low 25(OH)D is a consequence of chronic inflammation rather than the cause. Research points to a bacterial etiology pathogenesis for an inflammatory disease process which results in high 1,25(OH)2D and low 25(OH)D. Immunotherapy, directed at eradicating persistent intracellular pathogens, corrects dysregulated vitamin D metabolism and resolves inflammatory symptoms.

Candida albicans and cancer: Can this yeast induce cancer development or progression?

There is currently increasing concern about the relation between microbial infections and cancer. More and more studies support the view that there is an association, above all, when the causal agents are bacteria or viruses. This review adds to this, summarizing evidence that the opportunistic fungus Candida albicans increases the risk of carcinogenesis and metastasis. Until recent years, Candida spp. had fundamentally been linked to cancerous processes as it is an opportunist pathogen that takes advantage of the immunosuppressed state of patients particularly due to chemotherapy. In contrast, the most recent findings demonstrate that C. albicans is capable of promoting cancer by several mechanisms, as described in the review: production of carcinogenic byproducts, triggering of inflammation, induction of Th17 response and molecular mimicry. We underline the need not only to control this type of infection during cancer treatment, especially given the major role of this yeast species in nosocomial infections, but also to find new therapeutic approaches to avoid the pro-tumor effect of this fungal species.

CD4+ T cell subset differentiation and avidity setpoint are dictated by the interplay of cytokine and antigen mediated signals

CD4(+) T cell differentiation has been shown to be regulated by the cytokine milieu present during activation as well as peptide MHC levels. However, the extent to which these two important regulatory signals work in concert to shape CD4(+) T cell function has not been investigated. Using a murine OT-II transgenic TCR model of in vitro differentiation, we demonstrate that the ability of CD4(+) T cells to commit to a distinct lineage, i.e. Th1 vs. Th2 vs. Th17, is restricted by the amount of peptide antigen present in the stimulating environment. In addition, whether cells succumb to inhibitory effects associated with high dose antigen is dependent on the array of cytokine signals encountered. Specifically, stimulation with high dose antigen in Th1 or Th17 conditions promoted efficient generation of functional cells, while Th2 polarizing conditions did not. Finally, we found that the peptide sensitivity of an effector cell was determined by the combined actions of cytokine and peptide level, with Th1 cells exhibiting the highest avidity, followed by Th17 and Th2 cells. Together, these data show that the interplay of antigen and cytokine signals shape both the differentiation fate and avidity setpoint of CD4(+) T cells.

Exposure to Bacillus anthracis capsule results in suppression of human monocyte-derived dendritic cells

The antiphagocytic capsule of Bacillus anthracis is a major virulence factor. We hypothesized that it may also mediate virulence through inhibition of the host's immune responses. During an infection, the capsule exists attached to the bacterial surface but also free in the host tissues. We sought to examine the impact of free capsule by assessing its effects on human monocytes and immature dendritic cells (iDCs). Human monocytes were differentiated into iDCs by interleukin-4 (IL-4) and granulocyte-macrophage colony-stimulating factor (GM-CSF) over 7 days in the presence of capsule derived from wild-type encapsulated B. anthracis Ames (WT) or a control preparation from an isogenic B. anthracis Ames strain that produces only 2% of the capsule of the WT (capA mutant). WT capsule consistently induced release of IL-8 and IL-6 while the capA mutant control preparation elicited either no response or only a minimal release of IL-8. iDCs that were differentiated in the presence of WT capsule had increased side scatter (SSC), a measure of cellular complexity, when assessed by flow cytometry. iDCs differentiated in the presence of WT capsule also matured less well in response to subsequent B. anthracis peptidoglycan (Ba PGN) exposure, with reduced upregulation of the chemokine receptor CCR7, reduced CCR7-dependent chemotaxis, and reduced release of certain cytokines. Exposure of naive differentiated control iDCs to WT capsule did not alter cell surface marker expression but did elicit IL-8. These results indicate that free capsule may contribute to the pathogenesis of anthrax by suppressing the responses of immune cells and interfering with the maturation of iDCs.