Project description:We set up to characterize the global transcriptome of splenic follicular (FO) B cells from control wild type (Wt) and Igha-deficient (IgAKO) mice with the aim of gaining new insights into how translocated gut antigens may impair IgG production to vaccines in the absence of IgA. Splenic Marginal zone (MZ) B cells were also included in this study, as IgA deficiency impaired IgG responses to T-independent immunogens as well.
2024-01-01 | GSE173361 | GEO
Project description:Spink4 modulates gut microbiota to interfere IgA production
Project description:Immunoglobulin A (IgA) most predominant antibody isotype at mucosal surfaces and is regulated by both T cell-dependent (TD) and independent (TI) mechanisms. In the TD pathway, T follicular helper (TFH) cells provide help to B cells to generate high-affinity antibodies. T follicular regulatory (TFR) cells fine-tune antibody responses, but precisely how these cellsregulate microbiota-directed IgA at mucosal sites has been unclear. Here, we used a TFR-deficient mouse model (Foxp3Cre Bcl6fl/fl; Bcl6FC) in which the gut microbiota develops in the absence of TFR cells, while the broader regulatory T cell compartment remains intact. While Bcl6FC mice showed similar levels of IgA-coated commensal bacteria to wild-type mice in the naïve state, following oral immunization, Bcl6FC mice exhibited a durable increase in IgA-coated commensal bacteria in feces and small intestine, without changes in overall community composition or epithelial barrier permeability. IgA-seq analysis of Bcl6FC mice revealed an increased diversity of IgA-coated taxa, both in naïve and orally immunized mice. IgA coating index analysis, a measure of IgA affinity, identified higher IgA binding to multiple taxa in Bcl6C mice compared to control mice. Consistent with these findings, sera from immunized Bcl6FC mice showed increased IgA binding to Alloprevotella and Klebsiella species but not to E. coli or Group A/B Streptococcus compared to control mice. B cell receptor repertoire sequencing demonstrated divergent patterns of somatic hypermutation (SMH) for IgA and IgG, where TFR cells repressed IgA SMH but enhanced IgG somatic hypermutation. Mechanistically, suppression of commensal-directed IgA required TFR-derived IL-10 but was independent of CTLA-4. IL-10 directly inhibited TGF-β-driven IgA class switching of B cells in vitro. Together, our data identify TFR cells as critical gatekeepers of mucosal IgA responses, constraining commensal-specific IgA responses through a novel IL-10-dependent pathway. Our findings haveimportant implications for regulation of the microbiome by TFR cells and IgA.
Project description:Immunoglobulin A (IgA)-producing plasma cells derived from conventional B cells in the gut play an important role in maintaining the homeostasis of gut flora. Both T cell-dependent and T cell-independent IgA class switching occurs in the lymphoid structures in the gut, whose formation depends on lymphoid tissue inducers (LTis), a subset of innate lymphoid cells (ILCs). However, our knowledge on the functions of ILCs, the innate counter parts of CD4 T helper cells, in promoting IgA production is still limited. By cell adoptive transfer and utilizing a unique mouse strain, we demonstrated that the generation of IgA-producing plasma cells from B cells in the gut occurred efficiently in the absence of both T cells and ILCs and without engaging TGFβ signaling. Nevertheless, B cell recruitment and/or retention in the gut required NKp46-CCR6+ LTis. Therefore, while ILCs contribute to the accumulation of B cells in the gut through inducing lymphoid structure formation, they are not essential for the T cell-independent generation of IgA-producing plasma cells.
Project description:IgA+ Plasma Cells were sort-purified from the small intestinal lamina prorpia of C57BL/6 mice at four Zeitgeber time points (ZT0, 6, 12 and 18). RNA extracted from these samples was subjected to bulk RNA seq to identify time of day differences in IgA+ PC gene expression.
Project description:Immunoglobulin A (IgA) is essential for mucosal immunity and is implicated in autoimmune diseases like IgA nephropathy (IgAN). Certain pathogenic and commensal bacteria produce IgA proteases (IgAPs) that selectively cleave IgA, potentially aiding bacterial colonization and offering therapeutic avenues for IgAN. Here, we investigate the substrate specificity of M64 family peptidases, focusing on the IgAP ThomasA from Thomasclavelia ramosa and BF3526 from Bacteroides fragilis. Structural, biochemical, and mutagenesis data demonstrate that ThomasA cleaves IgA through exclusive recognition of the Fab region—a mechanism distinct from other antibody-specific peptidases, which typically require engagement of the Fc region. In contrast, X-ray crystal structures of BF3526 in complex with substrate and product peptides, together with enzymology assays, show that this enzyme targets the N-terminus of predigested proteins. These findings reveal divergent substrate recognition strategies within the M64 family and provide structural insight into their conserved catalytic mechanism. Together, they enhance our understanding of bacterial adaptation and support the rational design of enzymes for IgA-mediated autoimmune diseases. The LC-MS data associated with the project is included in the current dataset.
Project description:Determine whether IgA B cells are derived from IgE B cells during allergy; understand whether IgE and IgA B cells induced during allergy share clonal relationships in the gut.
Project description:Determine whether IgA B cells are derived from IgE B cells during allergy; understand whether IgE and IgA B cells induced during allergy share clonal relationships in the gut.