Tu165 - Heterogeneous Regulation of IL-10 Expression in B-cell Subsets

Nicholas Vonniessen – Research Institute of the McGill University Health Centre, Department of Pediatrics and Experimental Medicine, Faculty of Medicine, McGill University, Montreal, Canada; Wei Zhao – Research Institute of the McGill University Health Centre, Department of Pediatrics and Experimental Medicine, Faculty of Medicine, McGill University, Montreal, Canada; Bruce Mazer – Research Institute of the McGill University Health Centre, Department of Pediatrics and Experimental Medicine, Faculty of Medicine, McGill University, Montreal, Canada

Abstract Text: Regulatory B-cells (Bregs) are a heterogeneous cell subset of growing interest with the capacity to supress inflammatory responses. The most studied class of Bregs are those defined by the expression of interleukin-10 (IL-10), however B-cell subsets which express IL-10 and their mechanism of IL-10 induction remains unclear. Toll-like receptor activation is known to induce IL-10 expression in both mouse and human B-cells, with CpG – a TLR9 agonist – commonly used to induce Bregs in vitro. In this study, we use CpG to induce and study IL-10 regulation across mouse B-cell subsets, identify signalling pathways crucial for IL-10 expression, and explore transcriptomic relationships between IL-10+ B-cells derived from multiple B-cell subsets. Using primary cells from IL-10-reporter mice, we have found that mouse B-cell subsets differ in their capacity to express IL-10 in response to CpG stimulation. Splenic marginal zone (40% IL-10+) and splenic B1 cells (50% IL-10+), and peritoneal B1 cells (70% IL-10+) exhibit the greatest IL-10 competence compared to follicular B (10% IL-10+) and peritoneal B2 (25% IL-10+) subsets after 48 hours. Peritoneal B-cells were capable of upregulating IL-10 expression more rapidly than splenic B-cells, and IL-10 induction in splenic B-cells was p38 dependent. Breg gene expression significantly differed based on the originating subset. Our results show that cell-intrinsic heterogeneity contributes to Breg heterogeneity in behaviour and phenotype, significantly influencing IL-10-competence. This work highlights the necessity of deconvoluting heterogeneous cell responses to better understand mechanisms of gene regulation due to the significant differences between lymphoid and circulating B-cell populations.