Unusual biochemical features and follicular dendritic cell expression of human Fcalpha/mu receptor.

The Fc receptor for IgA and IgM (Fcalpha/muR) is of particular interest because it can bind antibodies of both IgM and IgA isotypes and thus may play a pivotal role in systemic and mucosal immunity. Using IgM and IgA ligands and newly generated Fcalpha/muR specific monoclonal antibodies we have defined biochemical features and cellular distribution of the human Fcalpha/muR. Both recombinant and native forms of human Fcalpha/muR are expressed on the cell surface as remarkably stable homodimeric transmembrane glycoproteins that can bind specifically polymeric IgM or IgA.