The generation of haemolytic plaque-forming cells from human tonsils.

At low cell numbers (2 X 10(6) cells/culture) good numbers of plaque-forming cells (PFC) were obtained in response to stimulation by pokeweed mitogen (PWM). Maximum PFC were obtained with the Marbrook chamber using 2 X 10(6) cells/culture, stimulating cells with a 1:50 dilution of PWM and harvesting after 6--7 days. 20 different experiments using standard conditions gave a geometric mean of 646 PFC/10(6) initial cells. All PFC detected were IgM.