Fate of antibodies bound to lymphocyte surface. I.--Study with complement-dependent cytotoxicity, indirect immunofluorescence and radiolabelled antibodies.

Anti-HL-A alloantiserum, heterologous antilymphocyte globulins and anti-beta2m antisera were allowed to react to human lymphocytes in vitro. The fate of the antigen-antibody complexes formed at the cell surface has been studied by means of the lymphocytoxicity test in the presence of rabbit complement, radiolabelled antibodies and the indirect immunofluorescence technique. Those techniques demonstrated that initially bound antibodies disappear from the cell surface. This disappearance requires optimal conditions; it does not result from a mere dissociation of antibodies but likely represents partial degradation, internalization and release of antigen-antibody complexes into the extracellular medium. This phenomenon can be regarded as a reflection of the dynamic state of the cell membrane, although it differs from the redistribution of antigen-antibody complexes on the lymphocyte surface (patching and capping). Possible implications of such events are discussed in relation to triggering or blocking of lymphocyte proliferation.