Activation of B lymphocytes by locally concentrated concanavalin A

B lymphocytes are not stimulated by soluble concanavalin A (Con A). However, Con A cross‐linked at the bottom of tissue culture petri dishes could activate DNA synthesis in B cells. Addition of free Con A to such cultures inhibited the proliferative response to insoluble Con A. T lymphocytes were not activated by locally concentrated Con A, although they responded to soluble Con A. In the presence of both soluble and cross‐linked Con A there was a shift in the dose response curve to soluble Con A, the magnitude of which varied with the concentration of cross‐linked Con A.