Sperm exposure to accessory gland secretions alters the transcriptomic response of the endometrium in cattle

In a recent study from our group, mating to intact, but not vasectomised, bulls modified the endometrial transcriptome, suggesting an important role of sperm in the modulation of the uterine environment in this species. However, it is not clear whether these changes are driven by intrinsic sperm factors, or by factors of accessory gland (AG) origin that bind to sperm at ejaculation. Thus, the aim of the present study was to determine whether ejaculated sperm, which are suspended in the secretions of the AGs, elicit a different endometrial transcriptomic response than epididymal sperm, which have never been exposed to AG factors. To this end, bovine endometrial explants collected from heifers in oestrus were incubated alone (control), or with epididymal or ejaculated sperm. RNA-sequencing revealed 1912 differentially expressed genes (DEGs) between in endometrial explants exposed to epididymal sperm compared with control explants, whereas 115 DEGs genes detected between endometrial explants exposed to ejaculated sperm in comparison to control explants. In both cases, the top pathways associated with these genes included T cell regulation and NF-KB and IL17 signalling. To confirm whether AG factors were directly responsible for the dampening of the endometrial response elicited by ejaculated sperm, endometrial explants were incubated with epididymal sperm previously exposed, or not, to seminal plasma (SP). Exposure to SP abrogated the downregulation of SQSTM1 by epididymal sperm, and partially inhibited the upregulation of MYL4 and CHRM3 and downregulation of SCRIB. These data indicate that factors of AG origin modulate the interaction between sperm and the endometrium in cattle.

Epithelial MHC class II directs microbiota-specific intestinal immune homeostasis

Dysregulated immune responses to resident microbes promote pathologic inflammation, however, the mechanisms instructing commensal-specific T cells remain poorly understood. Here, we find that non-hematopoietic intestinal epithelial cells (IECs) represent the primary cells expressing major histocompatibility complex (MHC) II at the intestinal host-microbiota interface. Interestingly, epithelial MHCII and commensal-specific CD4+ T cells were concurrently induced by post-natal microbiota colonization, provoking the hypothesis that epithelial MHCII regulates local commensal-specific CD4+ T cells. While MHCII on classical antigen presenting cells directs expansion of antigen-specific CD4+ T cells, loss of IEC-intrinsic MHCII surprisingly led to elevated commensal-specific CD4+ T cells in the intestine. Further, epithelial MHCII expression actively limited accumulation of antigen-specific CD4+ T cells in adult mice. Expansion of commensal-specific Th17 cells was restricted by epithelial MHCII, and remarkably mice lacking epithelial MHCII were highly susceptible to microbiota-triggered inflammation. Collectively, these data indicate that impaired epithelial MHCII-T cell regulation within mucosal tissues alters microbiota-specific immunity and predisposes to chronic inflammation.

The Dynamics of B Cell Aging in Health and Disease

Aging is considered to be an important risk factor for several inflammatory diseases. B cells play a major role in chronic inflammatory diseases by antibody secretion, antigen presentation and T cell regulation. Different B cell subsets have been implicated in infections and multiple autoimmune diseases. Since aging decreases B cell numbers, affects B cell subsets and impairs antibody responses, the aged B cell is expected to have major impacts on the development and progression of these diseases. In this review, we summarize the role of B cells in health and disease settings, such as atherosclerotic disease. Furthermore, we provide an overview of age-related changes in B cell development and function with respect to their impact in chronic inflammatory diseases.

Characterization of human FDCs reveals regulation of T cells and antigen presentation to B cells

Stromal-derived follicular dendritic cells (FDCs) are essential for germinal centers (GCs), the site where B cells maturate their antibodies. FDCs present native antigen to B cells and maintain a CXCL13 gradient to form the B cell follicle. Yet despite their essential role, the transcriptome of human FDCs remains undefined. Using single-cell RNA sequencing and microarray, we provided the transcriptome of these enigmatic cells as a comprehensive resource. Key genes were validated by flow cytometry and microscopy. Surprisingly, marginal reticular cells (MRCs) rather than FDCs expressed B cell activating factor (BAFF). Furthermore, we found that human FDCs expressed TLR4 and can alter antigen availability in response to pathogen-associated molecular patterns (PAMPs). High expression of PD-L1 and PD-L2 on FDCs activated PD1 on T cells. In addition, we found expression of genes related to T cell regulation, such as HLA-DRA, CD40, and others. These data suggest intimate contact between human FDCs and T cells.

MERTK on mononuclear phagocytes regulates T cell antigen recognition at autoimmune and tumor sites

Understanding mechanisms of immune regulation is key to developing immunotherapies for autoimmunity and cancer. We examined the role of mononuclear phagocytes during peripheral T cell regulation in type 1 diabetes and melanoma. MERTK expression and activity in mononuclear phagocytes in the pancreatic islets promoted islet T cell regulation, resulting in reduced sensitivity of T cell scanning for cognate antigen in prediabetic islets. MERTK-dependent regulation led to reduced T cell activation and effector function at the disease site in islets and prevented rapid progression of type 1 diabetes. In human islets, MERTK-expressing cells were increased in remaining insulin-containing islets of type 1 diabetic patients, suggesting that MERTK protects islets from autoimmune destruction. MERTK also regulated T cell arrest in melanoma tumors. These data indicate that MERTK signaling in mononuclear phagocytes drives T cell regulation at inflammatory disease sites in peripheral tissues through a mechanism that reduces the sensitivity of scanning for antigen leading to reduced responsiveness to antigen.

The Inflammatory Processes Driven by Gut Microbiota

Microbiome studies have shown alterations in bacterial communities in the state of many diseases, including inflammatory bowel disease, metabolic disorders, autoimmune diseases, neurodegenerative diseases, and cancer. Chronic inflammation is a common promoter of many of these pathological processes. Shifting in the microbial diversity is also known as dysbiosis. Dysbiosis, increased detrimental bacterial products, decreased favorable microbial metabolites, interrupted tissue barriers, and bacterial translocation cause excessive immune response and inflammation. Several mechanisms play a role to maintain intestinal homeostasis by limiting bacterial translocation from the intestinal lumen into the lamina propria. Among these mechanisms, most importantly, the mucosal barrier that consists of the antimicrobial peptides, mucus, and immunoglobulin A is fundamental to protect epithelial barrier integrity to reduce the excessive immune response. Moreover, recognizing bacteria and metabolites through receptors results in T cell regulation and immune modulation, which is the keystone of the controlled immune response. This review summarizes the anti-inflammatory and pro-inflammatory mechanisms driven by gastrointestinal microbiota, and it also highlights the recent approaches, including epigenetics and precision medicine.

NKG2D Enhances Double-Negative T Cell Regulation of B Cells

Numerous studies reported a small subpopulation of TCRαβ+CD4-CD8- (double-negative) T cells that exert regulatory functions in the peripheral lymphocyte population. However, the origin of these double-negative T (DNT) cells is controversial. Some researchers reported that DNT cells originated from the thymus, and others argued that these cells are derived from peripheral immune induction. We report a possible mechanism for the induction of nonregulatory CD4+ T cells to become regulatory double-negative T (iDNT) cells in vitro. We found that immature bone marrow dendritic cells (CD86+MHC-II- DCs), rather than mature DCs (CD86+MHC-II+), induced high levels of iDNT cells. The addition of an anti-MHC-II antibody to the CD86+MHC-II+ DC group significantly increased induction. These iDNT cells promoted B cell apoptosis and inhibited B cell proliferation and plasma cell formation. A subgroup of iDNT cells expressed NKG2D. Compared to NKG2D- iDNT cells, NKG2D+ iDNT cells released more granzyme B to enhance B cell regulation. This enhancement may function via NKG2D ligands expressed on B cells following lipopolysaccharide stimulation. These results demonstrate that MHC-II impedes induction, and iDNT cells may be MHC independent. NKG2D expression on iDNT cells enhanced the regulatory function of these cells. Our findings elucidate one possible mechanism of the induction of peripheral immune tolerance and provide a potential treatment for chronic allograft rejection in the future.

PD-1 dependent expansion of Amphregulin+FOXP3+ cells is associated with oral immune dysfunction in HIV patients on therapy

Residual systemic inflammation and mucosal immune dysfunction persist in people living with HIV (PLWH) despite treatment with combined anti-retroviral therapy (cART), but the underlying immune mechanisms are poorly understood. Here we report an altered immune landscape involving upregulation of TLR- and inflammasome signaling, localized CD4+ T cell hyperactivation, and counterintuitively, an enrichment of CD4+CD25+FOXP3+ regulatory T cells (Tregs) in the oral mucosa of HIV+ patients on therapy. Using human oral tonsil cultures, we found that HIV infection causes an increase in a unique population of FOXP3+ cells expressing PD-1, IFN-γ, Amphiregulin (AREG), and IL-10. These cells persisted even in the presence of the anti-retroviral drug and underwent further expansion driven by TLR-2 ligands and IL-1β. IL-1β also promoted PD-1 upregulation in AKT1 dependent manner. PD-1 stabilized FOXP3 and AREG expression in these cells through a mechanism requiring the activation of Asparaginyl Endopeptidase (AEP). Importantly, these FOXP3+ cells were incapable of suppressing CD4+ T cells in vitro. Concurrently, HIV+ patients harbored higher levels of PD-1, IFN-γ, Amphiregulin (AREG), and IL-10 expressing FOXP3+ cells, which strongly correlated with CD4+ T cell hyperactivation, suggesting an absence of CD4+ T cell regulation in the oral mucosa. Taken together, this study provides insights into a novel mechanism of FOXP3+ cell dysregulation and reveals a critical link in the positive feedback loop of oral mucosal immune activation events in HIV+ patients on therapy.One Sentence SummaryHIV-induced immune dysfunction in lymphoid and mucosal tissues

Identification of potential proteases for abdominal aortic aneurysm by weighted gene coexpression network analysis

Proteases are involved in the degradation of the extracellular matrix (ECM), which contributes to the formation of abdominal aortic aneurysm (AAA). To identify new disease targets in addition to the results of previous microarray studies, we performed next-generation sequencing (NGS) of the whole transcriptome of Angiotensin II-treated ApoE−/− male mice (n = 4) and control mice (n = 4) to obtain differentially expressed genes (DEGs). Identified DEGs of proteases were analyzed using weighted gene coexpression network analysis (WGCNA). RT-qPCR was conducted to validate the differential expression of selected hub genes. We found that 43 DEGs were correlated with the expression of the protease profile, and most were clustered in immune response module. Among 26 hub genes, we found that Mmp16 and Mmp17 were significantly downregulated in AAA mice, while Ctsa, Ctsc, and Ctsw were upregulated. Our functional annotation analysis of genes coexpressed with the five hub genes indicated that Ctsw and Mmp17 were involved in T cell regulation and Cell adhesion molecule pathway, respectively, and that both were involved in general regulation of the cell cycle and gene expression. Overall, our data suggest that these ectopic genes are potentially crucial to AAA formation and may act as biomarkers for the diagnosis of AAA.