Phytohemagglutinin activation of lymphocytes: quantitative comparison of different preparations

Lymphocytes from 12 normal subjects were stimulated in vitro with several concentrations of six commercial preparations of phytohemagglutinin and one column-purified preparation. All preparations produced activation profiles that were highly concentration dependent, with diminished activation at concentrations greater than the optimal concentration. The preparations differed markedly in their mitogenic capacities. Several concentrations of phytohemagglutinin should be employed when lymphocyte activation in vitro is studied as an index of cell-mediated immunity.