Regulatory B10 cells within the peritoneal cavity delay colitis onset by altering local T cell-specific IFNγ production (166.1)

Abstract B cells mediate multiple functions that influence immune and inflammatory responses. A rare subset of splenic CD1dhiCD5+ B cells with capacity to produce IL-10 (B10 cells) has been found to regulate T cell responses, inflammation and autoimmunity. Relative to the spleen, higher frequencies of B cells produce IL-10 in the peritoneal cavity (PC) upon a combined in vitro LPS, PMA and Ionomycin stimulation for 5 hours. In this study, the phenotypic and functional characteristics of IL10-competent B10 cells within the PC (PC B10 cells) were characterized. PC B10 cells share several phenotypic markers with splenic B10 cells, and were found within the phenotypically defined B1a (46%), B1b (28%) and B2 (5%) subsets. Adoptive transfer of PC B10 cells significantly delayed disease onset and severity in both the IL10-/- mouse model of spontaneous colitis and the model of induced colitis through transfer of CD4+CD25-CD45RBhi into Rag-/- mice. Overall, when PC B10 cells were transferred i.p. into both disease model recipient mice, the number of activated and IFNγ-producing CD4+ cells significantly decreased in the PC and mesenteric lymph nodes. Thereby, PC B10 cells significantly modulate T cell pathogenicity during colitis.