The glycolipid exoantigen derived from Chlamydia muridarum activates invariant natural killer T cells

Intestinal mucosal immunity and type 1 diabetes: Non-negligible communication between gut and pancreas

Type 1 diabetes (T1D) is a chronic autoimmune disease characterized by T cell-mediated pancreatic β cell loss, resulting in lifelong absolute insulin deficiency and hyperglycaemia. Environmental factors are recognized as a key contributor to the development of T1D, with the gut serving as a primary interface for environmental stimuli. Recent studies have revealed that the alterations in the intestinal microenvironment profoundly affect host immune responses, contributing to the aetiology and pathogenesis of T1D. However, the dominant intestinal immune cells and the underlying mechanisms remain incompletely elucidated. In this review, we provide an overview of the possible mechanisms of the intestinal mucosal system that underpin the pathogenesis of T1D, shedding light on the roles of both non-classical and classical immune cells in T1D. Our goal is to gain insights into how modulating these immune components may hold potential implications for T1D prevention and provide novel perspectives for immune-mediated therapy.

Non-targeted metabolomics analysis of fermented traditional Chinese medicine and its impact on growth performance, serum biochemistry, and intestinal microbiome of weaned lambs

Fermented traditional Chinese medicines (TCMs) have been identified as a low-cost and promising feed additive to to alleviate weaning stress in young livestock and poultry effectively. This study investigated the impact of probiotic fermentation on the metabolite content of BanQi (Radix Isatidis and Astragalus membranaceus) extract while also examined the effects of both fermented-BanQi (FBQ) and unfermented-BanQi (UBQ) on growth performance, serum biochemistry, intestinal villi, and gut microbiota in weaned lambs. This study demonstrated that compared with UBQ, FBQ contained significantly higher levels of free amino acids (e.g., phenylalanine and isoleucine), short peptides (e.g., Val-Leu-Pro-Val-Pro-Gln and Gly-Leu), and the active ingredients (e.g., vindesine and reserpine) (P < 0.05). The addition of FBQ to the diet significantly increased the final body weight and average daily gain of weaned lambs (P < 0.05). In addition, FBQ significantly increased the total protein level in the serum and the villus length of the jejunum and ileum in lambs, while significantly reduced the levels of aspartate aminotransferase (AST) and urea (P < 0.05). Sequencing of the intestinal flora showed that FBQ improved the diversity of intestinal flora and promoted the enrichment of beneficial bacteria in the lamb intestine, such as Mogibacterium and Butyrivibrio, compared to NC or UBQ groups (P < 0.05). Fermentation with Bacillus subtilis can enhance the content of free amino acids, peptides, and active ingredients in BanQi extract, making it an effective method to improve the efficacy of traditional Chinese medicine. Adding FBQ to the diet can improve the growth performance of weaned lambs, and its mechanism may be related to increasing the height of intestinal villi and increasing the diversity of intestinal flora.

Causal role of immune cells in alopecia areata: A two-sample Mendelian randomization study

BACKGROUND

Previous research has highlighted an association between alopecia areata (AA) and the collapse of hair follicle immune privilege, however, the causal linkage to specific immune cell traits remains to be elucidated. This study aimed to investigate the causal influence of immune cell traits on AA utilizing a two-sample Mendelian randomization (MR) approach.

METHODS

Leveraging GWAS summary statistics of 731 immunological traits (n = 3757) and AA data (n = 211,428), MR analyses were conducted employing inverse-variance weighted (IVW), weighted median, and MR-Egger regression methodologies. Sensitivity analyses were undertaken using Cochran's Q test, MR-Egger intercept test, and MR-PRESSO analysis. A reverse MR analysis was performed for immune cell traits identified in the initial MR analysis.

RESULTS

Our study unveiled multiple immune traits associated with AA. Protective associations were observed for CD62L- CD86+ myeloid dendritic cells (DCs), TD CD4+%CD4+ T cells, and others, with ORs ranging from 0.63 to 0.78. Conversely, traits like CD62L on CD62L+ plasmacytoid DCs, HLA-DR on CD14- CD16+ monocytes, HLA-DR on monocytes, and others, were determined to augment the risk of AA, with ORs ranging from 1.13 to 1.46. Reverse MR analysis signified a reduction in BAFF-R on IgD-CD24-B cells post-AA onset (OR: 0.97, 95% CI: 0.95-1.00), with no identified heterogeneity or horizontal pleiotropy among the instrumental variables (IVs).

CONCLUSIONS

Our findings suggests that CD62L on certain subpopulations of DCs and HLA-DR on monocytes may epitomize risk factors for AA, offering potential therapeutic targets for alleviating AA.

Pathogenic NKT cells attenuate urogenital chlamydial clearance and enhance infertility

Urogenital chlamydial infections continue to increase with over 127 million people affected annually, causing significant economic and public health pressures. While the role of traditional MHCI and II peptide presentation is well defined in chlamydial infections, the role of lipid antigens in immunity remains unclear. Natural killer (NK) T cells are important effector cells that recognize and respond to lipid antigens during infections. Chlamydial infection of antigen-presenting cells facilitates presentation of lipid on the MHCI-like protein, CD1d, which stimulates NKT cells to respond. During urogenital chlamydial infection, wild-type (WT) female mice had significantly greater chlamydial burden than CD1d-/- (NKT-deficient) mice, and had significantly greater incidence and severity of immunopathology in both primary and secondary infections. WT mice had similar vaginal lymphocytic infiltrate, but 59% more oviduct occlusion compared to CD1d-/- mice. Transcriptional array analysis of oviducts day 6 post-infection revealed WT mice had elevated levels of Ifnγ (6-fold), Tnfα (38-fold), Il6 (2.5-fold), Il1β (3-fold) and Il17a (6-fold) mRNA compared to CD1d-/- mice. In infected females, oviduct tissues had an elevated infiltration of CD4+ -invariant NKT (iNKT) cells, however, iNKT-deficient Jα18-/- mice had no significant differences in hydrosalpinx severity or incidence compared to WT controls. Lipid mass spectrometry of surface-cleaved CD1d in infected macrophages revealed an enhancement of presented lipids and cellular sequestration of sphingomyelin. Taken together, these data suggest an immunopathogenic role for non-invariant NKT cells in urogenital chlamydial infections, facilitated by lipid presentation via CD1d via infected antigen-presenting cells.

Die Kämpfe únd schláchten-the struggles and battles of innate-like effector T lymphocytes with microbes

The large majority of lymphocytes belong to the adaptive immune system, which are made up of B2 B cells and the αβ T cells; these are the effectors in an adaptive immune response. A multitudinous group of lymphoid lineage cells does not fit the conventional lymphocyte paradigm; it is the unconventional lymphocytes. Unconventional lymphocytes-here called innate/innate-like lymphocytes, include those that express rearranged antigen receptor genes and those that do not. Even though the innate/innate-like lymphocytes express rearranged, adaptive antigen-specific receptors, they behave like innate immune cells, which allows them to integrate sensory signals from the innate immune system and relay that umwelt to downstream innate and adaptive effector responses. Here, we review natural killer T cells and mucosal-associated invariant T cells-two prototypic innate-like T lymphocytes, which sense their local environment and relay that umwelt to downstream innate and adaptive effector cells to actuate an appropriate host response that confers immunity to infectious agents.

Cross Talk Between Natural Killer T and Dendritic Cells and Its Impact on T Cell Responses in Infections

Both innate and adaptive immunity is vital for host defense against infections. Dendritic cells (DCs) are critical for initiating and modulating adaptive immunity, especially for T-cell responses. Natural killer T (NKT) cells are a small population of innate-like T cells distributed in multiple organs. Many studies have suggested that the cross-talk between these two immune cells is critical for immunobiology and host defense mechanisms. Not only can DCs influence the activation/function of NKT cells, but NKT cells can feedback on DCs also, thus modulating the phenotype and function of DCs and DC subsets. This functional feedback of NKT cells on DCs, especially the preferential promoting effect on CD8α+ and CD103+ DC subsets in lymphoid and non-lymphoid tissues, significantly impacts the systemic and local adaptive CD4 and CD8 T cell responses in infections. This review focuses on the two-way interaction between NKT cells and DCs, emphasizing the importance of NKT cell feedback on DCs in bridging innate and adaptive immune responses for host defense purposes.

IL-27/IL-27R Mediates Protective Immunity against Chlamydial Infection by Suppressing Excessive Th17 Responses and Reducing Neutrophil Inflammation

IL-27, a heterodimeric cytokine of the IL-12 family, has diverse influences on the development of multiple inflammatory diseases. In this study, we identified the protective role of IL-27/IL-27R in host defense against Chlamydia muridarum respiratory infection and further investigated the immunological mechanism. Our results showed that IL-27 was involved in C. muridarum infection and that IL-27R knockout mice (WSX-1^-/- mice) suffered more severe disease, with greater body weight loss, higher chlamydial loads, and more severe inflammatory reactions in the lungs than C57BL/6 wild-type mice. There were excessive IL-17-producing CD4⁺ T cells and many more neutrophils, neutrophil-related proteins, cytokines, and chemokines in the lungs of WSX-1^-/- mice than in wild-type mice following C. muridarum infection. In addition, IL-17/IL-17A-blocking Ab treatment improved disease after C. muridarum infection in WSX-1^-/- mice. Overall, we conclude that IL-27/IL-27R mediates protective immunity during chlamydial respiratory infection in mice by suppressing excessive Th17 responses and reducing neutrophil inflammation.

The dialogue between unconventional T cells and the microbiota

The mammalian immune system is equipped with unconventional T cells that respond to microbial molecules such as glycolipids and small-molecule metabolites, which are invisible to conventional CD4 and CD8 T cells. Unconventional T cells include invariant natural killer T (iNKT) cells and mucosa-associated invariant T (MAIT) cells, which are involved in a wide range of infectious and non-infectious diseases, such as cancer and autoimmunity. In addition, their high conservation across mammals, their restriction by non-polymorphic antigen-presenting molecules, and their immediate and robust responses make these 'innate' T cells appealing targets for the development of one-size-fits-all immunotherapies. In this review, we discuss how iNKT and MAIT cells directly and indirectly detect the presence of and respond to pathogenic and commensal microbes. We also explore the current understanding of the bidirectional relationship between the microbiota and innate T cells, and how this crosstalk shapes the immune response in disease.

Endogenous IL-17A mediated neutrophil infiltration by promoting chemokines expression during chlamydial lung infection

Chlamydia is an obligate intracellular bacteria, which can infect cervix, urethra, conjunctiva, joints, lungs and so on. Neutrophils are important in host protection against microbial invasion during the early phase of infection. Here, to investigate the mechanism of IL-17A in recruiting neutrophils during Chlamydia muridarum (Cm) lung infection, we introduced IL-17A antibodies and IL-17^-/- mice to confirm the effect of IL-17A on influencing neutrophil attractants expressions. From the analysis of the data, we found that showed that Cm infection could upregulate the expression of neutrophil-related chemokines such as KC, MIP-2 and IL-6, as well as adhesion molecules including ICAM-1 and VCAM-1. With blocking endogenous IL-17A, the upregulated MIP-2 and IL-6 were decreased, which induced less neutrophil recruitment in lung. Comparing to WT mice, IL-17^-/- mice showed decreased infiltration of neutrophils in lung during the early phase of Cm infection, which were accordant with decreased chemokines, such as KC, MIP-2 and IL-6 expression. Whereas, the expression of adhesion molecules including ICAM and VCAM-1 in lungs were significantly increased in IL-17^-/- mice comparing to WT mice during Cm lung infection. The results demonstrated that IL-17A influenced neutrophil infiltration by affecting expression of chemokines and adhesion molecules during the early phase of chlamydial lung infection.

Genital tract lesions in sexually mature Göttingen minipigs during the initial stages of experimental vaginal infection with Chlamydia trachomatis serovar D

Background

Chlamydia is one of the most common sexually transmitted diseases in humans worldwide, causing chronic lesions in the reproductive tract. Due to its often asymptomatic course, there is limited knowledge about the initial changes in the genital tract following infection. This study employs a novel sexually mature minipig model to investigate the initial histopathological changes following vaginal infection with Chlamydia trachomatis serovar D.

Results

A vaginal inoculation resulted in an infection primarily affecting the lower genital tract. The histopathological changes were characterized by a subepithelial inflammation consisting of neutrophils and mononuclear cells, followed by an increase in the number of plasma cells within the sub-epithelial stroma of the vagina. Detection of Chlamydia was associated with expression of cyclooxygenase-2 and interleukin-8 by superficial epithelial cells. The infection was self-limiting, with a duration of 7 days.

Conclusion

Neutrophils, plasma cells and IL-8 have been linked with Chlamydia genital infection of unknown duration in human patients. In this study, we observe a similar pattern of local immune response/inflammation following experimental inoculation suggesting this porcine model shows promise as a model for translational chlamydia research.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-016-0793-6) contains supplementary material, which is available to authorized users.

From the Deep Sea to Everywhere: Environmental Antigens for iNKT Cells

Invariant natural killer T (iNKT) cells are a unique subset of innate T cells that share features with innate NK cells and adaptive memory T cells. The first iNKT cell antigen described was found 1993 in a marine sponge and it took over 10 years for other, bacterial antigens to be described. Given the paucity of known bacterial iNKT cell antigens, it appeared as if iNKT cells play a very specialist role in the protection against few, rare and unusual pathogenic bacteria. However, in the last few years several publications painted a very different picture, suggesting that antigens for iNKT cells are found almost ubiquitous in the environment. These environmental iNKT cell antigens can shape the distribution, phenotype and function of iNKT cells. Here, these recent findings will be reviewed and their implications for the field will be outlined.

Dynamics of NKT-Cell Responses to Chlamydial Infection

Natural killer T (NKT) cells have gained great attention owing to their critical functional roles in immunity to various pathogens. In this review, we provide an overview of the current knowledge on the role of NKT cells in host defense against and pathogenesis due to Chlamydia, which is an intracellular bacterial pathogen that poses a threat to the public health worldwide. Accumulating evidence has demonstrated that NKT cells, particularly invariant NKT (iNKT) cells, play a crucial role in host defense against chlamydial infections, especially in C. pneumoniae infection. iNKT cells can promote type-1 protective responses to C. pneumoniae by inducing enhanced production of IL-12 by dendritic cells (DCs), in particular CD8α+ DCs, which promote the differentiation of naive T cells into protective IFN-γ-producing Th1/Tc1 type CD4+/CD8+ T cells. This iNKT-cell-mediated modulation of DC function is largely dependent upon CD40–CD40L interaction, IFN-γ production, and cell-to-cell contact. In addition, iNKT cells modulate the function of natural killer cells. NKT cells may be also involved in the pathogenesis of some chlamydial diseases by inducing different patterns of cytokine production. A better understanding of NKT-cell biology will enable us to rationally design prophylactic and therapeutic tools to combat infectious diseases.

Invariant Natural Killer T Cells Promote T Cell Immunity by Modulating the Function of Lung Dendritic Cells during Chlamydia pneumoniae Infection

In this study, we examined the effect of invariant natural killer T (iNKT) cells on the function of lung dendritic cells (LDCs) in eliciting protective immunity against Chlamydia pneumoniae (Cpn) lung infection. We employed a combination of approaches including the use of iNKT cell-deficient, Jα18-knockout (KO) mice and LDC adoptive transfer. We found that iNKT cells significantly altered the number, phenotype and cytokine profile of LDCs following infection. Furthermore, coculture of T cells with LDCs from Cpn-infected wild-type (WT) and KO mice induced type-1 and type-2 responses, respectively. More importantly, upon adoptive transfer, LDCs from Cpn-infected WT mice (WT-LDCs) conferred protective immunity, whereas LDCs from KO mice (KO-LDCs) increased the severity of disease after challenge infection. Further cytokine analyses of the lung tissues and lung-draining lymph node cells showed that KO-LDC-recipient mice exhibited a type-2 cytokine production pattern, while WT-LDC recipients exhibited a type-1 cytokine profile. Taken together, our results provide in vivo evidence that iNKT cells play a critical role in modulating LDC function to generate protective T-cell immunity, particularly in a clinically relevant intracellular bacterial infection.

Activation of CD1d-restricted natural killer T cells can inhibit cancer cell proliferation during chemotherapy by promoting the immune responses in murine mesothelioma

We studied the impact of natural killer T (NKT) cell activation by alpha-galactocysylceramide (α-GalCer, α-GC) on cancer cell repopulation during chemotherapy in murine mesothelioma. The number of NKT cells was found to be increased during the development of murine mesothelioma. NKT cells specifically recognize α-GC through CD1d resulting in their activation and expansion. Tumor-bearing mice were treated with chemotherapy once weekly, and α-GC was followed after each cycle of chemotherapy. Anti-tumor effect was evaluated on wild-type (WT) and CD1d knockout (CD1dKO) mice. Cancer cell proliferation and apoptosis were evaluated by Ki67 and TUNEL immunohistochemistry. CD4(+) and CD8(+) T cell proportion and activation in tumor, spleen, draining lymph node and peripheral blood were determined by flow cytometry, and gene expression of activated T cell-related cytokines was quantified by reverse transcription PCR. NKT cells were identified by CD1d-α-GC-tetramer staining. In WT mice, tumor growth delay was achieved by cisplatin (Cis), and this effect was improved in combination with α-GC, but α-GC alone had little effect. Cancer cell proliferation during chemotherapy was significantly inhibited by α-GC, while cancer cell death was significantly upregulated. α-GC following chemotherapy resulted in NKT cell expansion and an increase of interferon-γ production in the draining lymph node, blood and spleen. Gene expression of immune-associated cytokines was upregulated. Strikingly, the percentage of inducible T cell co-stimulator(+)CD4 T cells, Th17/Tc17 cells increased in splenocytes. In CD1d KO mice, however, Cis alone was less effective and Cis + α-GC provided no additional benefit over Cis alone. α-GC alone had minimal effect in both mice. NKT activation between cycles of chemotherapy could improve the outcome of mesothelioma treatment.

[iNKT cells participate in the exacerbation of systemic candidal infection]

Candida species are one major causal microorganism of hospital acquired bloodstream infections associated with high mortality. Phagocytes like neutrophils in innate immunity and CD4 T cells in acquired immunity have a major role in host defense immune response. It has been recently found that a type of innate-like lymphocyte called NKT cells respond against various organisms but its role in candidal infection remained unknown. Thus, we analyzed the role of NKT cells in the immune response against systemic candidiasis using mice deficient of NKT cells. In vivo studies revealed that invariant NKT cells play a limited role for controlling systemic candidal infection. On the other hand, studies looking at the role of glycolipid-activated NKT cells during candidal infection revealed that candida-infected mice injected with glycolipid had shorter survival period and greater number of fungal colonies in the kidney accompanied with reduced number of neutrophils in the blood and bone marrow. Surprisingly, glycolipid-mediated exacerbation of candidal infection was absent in IFNγ deficient mice. Co-infection of candida with intestinal commensals caused exacerbated infection in which IFNγ played a critical role in impairing fungal elimination. These results suggest that the excessive IFNγ released from candida and bacterial co-infection is a critical factor in worsening candidal infection.

Invariant natural killer T cells: boon or bane in immunity to intracellular bacterial infections?

Invariant natural killer T (iNKT) cells represent a specialized subset of innate lymphocytes that recognize lipid and glycolipid antigens presented to them by nonclassical MHC-I CD1d molecules and are able to rapidly secrete copious amounts of a variety of cytokines. iNKT cells possess the ability to modulate innate as well as adaptive immune responses against various pathogens. Intracellular bacteria are one of the most clinically significant human pathogens that effectively evade the immune system and cause a myriad of diseases of public health concern globally. Emerging evidence suggests that iNKT cells can confer immunity to intracellular bacteria but also inflict pathology in certain cases. We summarize the current knowledge on the contribution of iNKT cells in the host defense against intracellular bacterial infections, with a focus on the underlying mechanisms by which these cells induce protective or pathogenic reactions including the pathways of direct action (acting on infected cells) and indirect action (modulating dendritic, NK and T cells). The rational exploitation of iNKT cells for prophylactic and therapeutic purposes awaits a profound understanding of their functional biology.

The role of invariant natural killer T cells in microbial immunity

Invariant natural killer T cells (iNKT cells) are unique lymphocytes with characteristic features, such as expression of an invariant T-cell antigen receptor (TCR) α-chain, recognition of glycolipid antigens presented by CD1d molecules, and ability to rapidly produce large amounts of cytokines, including interferon-γ (IFN-γ) and interleukin 4 (IL-4) upon TCR stimulation. Many studies have demonstrated that iNKT cells participate in immune response against diverse microbes, including bacteria, fungi, protozoan parasites, and viruses. Generally, these cells play protective roles in host defense against infections. However, in some contexts they play pathogenic roles, by inducing or augmenting inflammation. Recent reports show that iNKT cells recognize glycolipid antigens from pathogenic bacteria including Streptococcus pneumoniae, and they contribute to host defense against infection. iNKT cell responses to these microbial glycolipid antigens are highly conserved between rodents and humans, suggesting that iNKT cells are evolutionally conserved because their invariant TCR is useful in detecting certain pathogens. Furthermore, glycolipid-mediated iNKT cell activation during immunization has adjuvant activity, enhancing humoral and cell-mediated responses. Therefore, iNKT cell activation is an attractive target for developing new vaccines for infectious diseases.

Interruption of CXCL13-CXCR5 axis increases upper genital tract pathology and activation of NKT cells following chlamydial genital infection

BACKGROUND

Regulation of immune responses is critical for controlling inflammation and disruption of this process can lead to tissue damage. We reported that CXCL13 was induced in fallopian tube tissue following C. trachomatis infection. Here, we examined the influence of the CXCL13-CXCR5 axis in chlamydial genital infection.

METHODOLOGY AND PRINCIPAL FINDINGS

Disruption of the CXCL13-CXCR5 axis by injecting anti-CXCL13 Ab to BALB/c mice or using Cxcr5-/- mice increased chronic inflammation in the upper genital tract (UGT; uterine horns and oviducts) after Chlamydia muridarum genital infection (GT). Further studies in Cxcr5-/- mice showed an elevation in bacterial burden in the GT and increased numbers of neutrophils, activated DCs and activated NKT cells early after infection. After resolution, we noted increased fibrosis and the accumulation of a variety of T cells subsets (CD4-IFNγ, CD4-IL-17, CD4-IL-10 & CD8-TNFα) in the oviducts. NKT cell depletion in vitro reduced IL-17α and various cytokines and chemokines, suggesting that activated NKT cells modulate neutrophils and DCs through cytokine/chemokine secretion. Further, chlamydial glycolipids directly activated two distinct types of NKT cell hybridomas in a cell-free CD1d presentation assay and genital infection of Cd1d-/- mice showed reduced oviduct inflammation compared to WT mice. CXCR5 involvement in pathology was also noted using single-nucleotide polymorphism analysis in C. trachomatis infected women attending a sub-fertility clinic. Women who developed tubal pathology after a C. trachomatis infection had a decrease in the frequency of CXCR5 SNP +10950 T>C (rs3922).

CONCLUSIONS/SIGNIFICANCE

These experiments indicate that disruption of the CXCL13-CXCR5 axis permits increased activation of NKT cells by type I and type II glycolipids of Chlamydia muridarum and results in UGT pathology potentially through increased numbers of neutrophils and T cell subsets associated with UGT pathology. In addition, CXCR5 appears to contribute to inter-individual differences in human tubal pathology following C. trachomatis infection.

Inhibitory function of interferon on hepatocarcinogenesis

OBJECTIVE

We examined the growth-inhibitory effect and the mechanism of action of type I interferon (IFN) in human liver cancer cell lines in vitro and in vivo.

METHODS

We examined the growth-inhibitory effect of 5 types of type I IFN preparations (e.g., pegylated, nonpegylated IFN-alpha, and IFN-beta) used for the treatment of chronic hepatitis C in 13 liver cancer cell lines in vitro. After liver cancer cells were transplanted into nude mice, various doses of IFN preparations were subcutaneously administered, and the antitumor effect was examined.

RESULTS

The growth-inhibitory effect of each preparation was different, but IFN-beta expressed the strongest effects in vitro. Induction of an inhibition of cell cycle progression at the G(1), S or G(2)/M phase with or without apoptosis was the mechanism of action of IFN. IFN preparations induced a dose-dependent decrease in tumor volume and weight by inducing tumor cell apoptosis in vivo, and tumor growth was effectively suppressed even at the clinical dose for chronic hepatitis C treatment. The antitumor effect of pegylated IFN was significantly stronger than that of nonpegylated IFN.

CONCLUSION

The data suggest potential clinical application of pegylated IFN for the prevention and treatment of hepatocellular carcinoma.