2.4G2, a monoclonal antibody to macrophage Fc gamma receptors, reacts with murine T cell Fc gamma receptors and IgG-binding factors.

In order to determine whether T cell Fc gamma receptors (Fc gamma R) and IgG-binding factors (IgG-BF) are structurally related, we searched for common antigens on these molecules. We found that the anti-macrophage Fc gamma 1/gamma 2bR monoclonal antibody 2.4G2 binds to similar determinant(s) on the macrophage-like J774 cells and on the Fc gamma R+ hybridoma T cells T2D4. On the T cell membrane, these determinants are associated with Fc gamma 1/gamma 2bR. They are absent on Fc gamma R- hybridoma T cells or the FcR- BW5147 thymoma cells. 2.4G2-reactive molecules were also detected in soluble material either extracted or released in the supernatant of Fc gamma R+ hybridoma T cells. 2.4G2-reactive molecules released in the supernatant of T2D4 cells could be absorbed on Sepharose beads coupled to rabbit IgG and they were recovered by acid elution. Conversely, Sepharose beads coupled to 2.4G2 retained molecules which had affinity for rabbit IgG, which suppressed an in vitro antibody response and which had the same molecular weight as IgG-BF. These results indicate that T cell Fc gamma R and IgG-BF share common epitopes and that 2.4G2 can serve as an anti-IgG-BF antibody.