The potentiation and inhibition by autologous red cells and platelets of human lymphocyte transformation induced by pokeweed mitogen concanavalin A, mercuric chloride, antigen, and mixed leucocyte culture

Abstract

Prior work on the potentiation of phytohaemagglutinin-induced human lymphocyte transformation by autologous red blood cells (RBC) and platelets prompted the present report.

Studies were performed on the effects of autologous RBC and platelets upon lymphocyte transformation induced by a variety of mitogenic stimuli, utilizing human peripheral blood lymphocytes free of RBC and platelets as the starting cell preparation. The mitogenic activity of pokeweed mitogen (PWM) is potentiated to maximum of 300% by RBC: lymphocyte ratios of 0·5–20:1. Potentiation of lymphocyte transformation induced by concanavalin A (CON-A) does not occur, but >50% inhibition is found at RBC: lymphocyte ratios of 5–10:1. The mitogenic activities of both PWM and CON-A are potentiated 200–400% by the presence of platelets in a platelet: lymphocyte ratio of 3–10:1; higher doses of platelets are consistently (PWM) or occasionally (CON-A) less stimulatory and may actually cause inhibition of lymphocyte transformation. In contrast to these phytomitogens, lymphocyte transformation induced by antigen (PPD) in optimum mitogenic doses is not potentiated by either RBC or platelets. RBC do not alter HgCl₂-induced lymphocyte transformation, but platelets cause modest potentiation. In mixed leucocyte cultures the presence of either autologous or allogeneic RBC or platelets markedly inhibits transformation (platelets > RBC).

These observations demonstrate that the presence of mitotically inert particles such as autologous RBC or platelets may profoundly affect lymphocyte transformation induced by a variety of mitogenic stimuli. Possible explanations for the mechanism of these effects are discussed. Since many methods of lymphocyte collection and preparation yield populations of lymphocytes significantly contaminated with RBC and/or platelets, comparative studies of human lymphocyte transformation in health and disease which do not remove these cellular contaminants or control their number are subject to the most tentative interpretation.