Invitro Stimulation Of Human Lymphocytes With Heterologous Antilymphocyte Sera - Evidence For A Specific Antigenic Receptor Mechanism

Heterologous antiserum prepared against human lymphocytes (ALS) 2 has been shown to stimulate lymphocyte proliferation in vitro , as measured by 3 H-thymidine incorporation into DNA (1). This reaction is assumed to follow binding of the ALS to the lymphocyte plasma membrane, an event which triggers cell division (2). We have observed that ALS prepared against human thymus or thymus-derived (T) lymphocytes stimulated proliferation of lymphocytes in vitro , whereas ALS prepared against human cultured lymphoid cell lines which originated from bone marrow-derived (B) lymphocytes did not or did so poorly in spite of the fact that both ALS bound equally well to lymphocyte plasma membranes. This observation suggests that binding of ALS to lymphocytes per se is not a sufficient stimulus to induce proliferation.