Modulation of human B-lymphocyte receptors for IgG does not affect HLA-DR antigens

Receptors for the Fc portion of immunoglobulin G (Fc gamma R) on the surface of human peripheral T cells can be modulated on contact with antigen-antibody immune complexes (IgG-IC). Our results demonstrate that the Fc gamma R present on the surface of human B cells are also modulated on exposure to IgG-IC. Furthermore, the expression of HLA-DR molecules is not affected by the IgG-IC induced disappearance of Fc gamma R. In fact, the percentage of HLA-DR-positive cells and the relative amount of HLA-DR molecules on individual B cells analysed by flow microfluorometry was shown not to be influenced by Fc gamma R modulation. Moreover, pretreatment of cells with monoclonal antibodies directed against non-polymorphic determinants of HLA-DR antigens did not prevent the binding of IgG-coated ox erythrocytes. These results argue against a structural relationship between Fc gamma R and HLA-DR molecules on the surface of the B-cell populations investigated here.