Non-identity of the triggering of activation of lymphocytes by anti-immunoglobulin and by antigen

Goat anti-rabbit immunoglobulins trigger DNA synthesis in lymph node cell populations. Premature removal of anti-immunoglobulin at three hours or even as late as the 31st hour of a 48 hour culture period resulted in a markedly diminished response. In contrast, within three hours after addition of antigen to cells its removal was without effect on the extent of activation. Similar results were obtained by using the delayed addition of competing ligands. More importantly, removal of anti-immunoglobulin from purified B cells at three hours resulted in virtually complete inhibition of activation whereas removal of antigen at three hours was without effect. Possible mechanisms to account for the difference in triggering of B cells are discussed.