Kinetics of inhibition of mitogen-induced proliferation of human lymphocytes by alpha 2-macroglobulin in serum-free medium.

The effect of alpha 2-macroglobulin (alpha 2M) on the ability of human lymphocytes to proliferate in response to stimuli by 3 mitogens, concanavalin A, phytohaemagglutinin and pokeweed mitogen was investigated in in vitro lymphocyte cultures in serum-free medium. The following experiments were performed: 1. lymphocytes were treated with alpha 2M prior to stimulation with the mitogens; 2. alpha 2M and mitogens were added simultaneously to the lymphocyte cultures; and 3. alpha 2M was added to the lymphocyte cultures after they were stimulated with the mitogens. In all cases, alpha 2M was found to inhibit mitogen induced proliferation of the lymphocytes as evaluated by (6-3H)-thymidine uptake of the cells. The mechanisms involved in the inhibition of lymphocyte proliferation by alpha 2M are discussed.