EFFECTS OF PURIFIED MITOGENIC PROTEINS (PA-1 AND PA-2) FROM POKEWEED ON HUMAN T-LYMPHOCYTES AND B-LYMPHOCYTES INVITRO

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  • 1 January 1976
    • journal article
    • research article
    • Vol. 26  (1) , 108-117
Abstract
Purified proteins (Pa-1 and Pa-2) from pokeweed were compared with commercial pokeweed mitogen (PWM-G) and other mitogens in their ability to stimulate human lymphocytes. Using cultures of T [thymus-derived] and B [bone marrow-derived] cells separated from tonsil lymphocytes, thymidine uptake, blast transformation and immunoglobulin (Ig) synthesis were measured. IgM and IgG was measured in supernates of stimulated cultures by radioimmunoassay. Pa-1, Pa-2 and PWM-G were potent mitogens for unseparated tonsil lymphocytes or nylon column purified T cells. Pa-2 was active at lower concentrations than Pa-1, and PWM-G was less potent than the purified mitogens. These 3 mitogens all stimulated unseparated lymphocytes to secrete large quantities of Ig (20-100 .mu.g/ml) during 7 days in culture. With increasing amounts of mitogens severe decreases in Ig synthesis were observed at day 6, even with doses which were still optimal for stimulation of thymidine uptake at days 3 and 6. With purified B cells (< 2% T cells) Pa-1 was the best mitogen for thymidine incorporation. The secretory response was very variable. In some experiments, B cells did not secrete Ig in response to mitogens; in other, Pa-1 was clearly more effective at stimulating secretion than Pa-2 or PWM-G, and in some experiments B cells were stimulated by all 3. In 1 experiment, Pa-1 stimulated prolymphocytic leukemia cells to blast transformation and the secretion of IgM. Pa-1, Pa-2 and PWM-G are much better activators of Ig synthesis in human cultures than either PHA [phytohemagglutinin] or [Serratia marcescens] LPS [lipopolysaccharide] and Pa-1 is the most reliable B-cell stimulant of the three.