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Increased serum IgA in Fc/R-deficient mice on the (129 x C57BL/6) F1 genetic background

Kurita, N;Honda, S;Shibuya, A;

Fc/R (CD351) is an Fc receptor for both IgA and IgM, which is abundantly expressed in the small intestine. However, the role of Fc/R in the intestinal tissue is largely unknown. Here, we found that Fc/R is highly expressed on follicular dendritic cells (FDCs) in Peyer’s patches (PP) in the small intestine. Fc/R-deficient mice on the (129 x C57BL/6) F1 background showed increased serum, but not fecal, IgA level in response to gut-oriented antigens. IgA(+) B cells were increased in PP, but not in the lamina propria, of Fc/R-deficient mice, which was attenuated after reduction of commensal microbiota by oral treatment with antibiotics. Analyses of bone marrow chimeric mice, in which either FDCs or blood cells or both lack the expression of Fc/R, suggested that FDCs, but not blood cells, were responsible for the increased serum IgA concentration in Fc/R-deficient mice. Moreover, Fc/R-deficient mice showed enhanced germinal center formation against commensal microbiota in PP. Thus, serum IgA production against gut-oriented antigens is negatively regulated by Fc/R on FDCs in the F1 mice.