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

Fc alpha/mu R (CD351) is an Fc receptor for both IgA and IgM, which is abundantly expressed in the small intestine. However, the role of Fc alpha/mu R in the intestinal tissue is largely unknown. Here, we found that Fc alpha/mu R is highly expressed on follicular dendritic cells (FDCs) in Peyer's patches (PP) in the small intestine. Fc alpha/mu 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 alpha/mu 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 alpha/mu R, suggested that FDCs, but not blood cells, were responsible for the increased serum IgA concentration in Fc alpha/mu R-deficient mice. Moreover, Fc alpha/mu 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 alpha/mu R on FDCs in the F1 mice. (C) 2014 Elsevier Ltd. All rights reserved.