Fc receptors on cultured myeloma and hybridoma cells

The specificity of the Fcγ receptors on the X63.Ag8.653 nonproducing myeloma cell line has been examined for binding to IgG1-, IgG2a-, and IgG2b-containing antigen antibody complexes. Complexes containing each of these subclasses bind, and the binding of each is inhibited by the others. Trypsin treatment did not inhibit the binding of any of these subclasses. Furthermore, the monoclonal anti-Fc receptor antibody 2.4G2 inhibits the binding of all three subclasses. These results, together with those of other investigators, suggest that there is a single FcR for IgG1, IgG2a, and IgG2b on mouseB cells which differs in its specificity from the macrophage FcγR. This is confirmed by the fact that a mutant IgG2b myeloma protein which binds to the macrophage Fcγ1/γ2b receptor does not bind to the FcγR on X63.Ag8.653.