Involvement of Fcα/μR (CD351) in autoantibody production.

Antibody exerts various immune responses via binding to Fc receptors expressed on immune cells. Although several reports have demonstrated that IgM prevents autoantibody production, the role of IgM Fc receptors is largely unknown. To analyze the involvement of Fcα/μR (CD351), an Fc receptor for IgM and IgA expressed on B cells and follicular dendritic cells (FDCs), in IgM-mediated suppression of autoantibody production, we generated mice deficient in Fcα/μR on the background of MRL/MpJ-Fas(lpr/lpr) (Fcamr(-/-)Fas(lpr/lpr)) mice.

Isolation and characterization of naïve follicular dendritic cells.

Follicular dendritic cells (FDC) are specialized antigen-presenting cells to cognate B cells in the follicle of the lymphoid tissues. FDC also support survival and proliferation of the B cells, leading to the germinal center formation. FDC therefore play a central role in humoral immune responses.

Requirement of the cytoplasmic portion for dimer formation of Fcalpha/micro receptor expressed on cell surface.

Fcalpha/mu receptor (Fcalpha/muR), an Fc receptor for IgA and IgM, is the only Fc receptor for IgM identified on hematopoietic cells in human and rodents and for IgA in rodents. Fcalpha/microR is a type 1 transmembrane protein containing one immunoglobulin-like domain in the extracellular portion. Both human and mouse Fcalpha/microR mediate endocytosis of the ligands IgA and IgM, for which the cytoplasmic portion of Fcalpha/microR is responsible.