Activation of lymphocytes by concanavalin A requires calcium ions

Mouse spleen cells were exposed to a short pulse of the mitogenic lectin concanavalin A (con A). After removal of con A mitogenesis was measured by the incorporation of tritiated thymidine into DNA. It was found: (a) the number of cells responding to con A was proportional to the time of exposure to con A; (b) exposure of cells to con A in the absence of extracellular calcium failed to initiate mitogenesis; (c) for a mitogenic effect an extracellular calcium concentration greater than 10(-5)M was required during the time that the cells were exposed to con A.