Concanavalin A induces Ca2+ mobilization, but only minimal inositol phospholipid breakdown in mouse B cells.

Concanavalin A (Con A) induces DNA synthesis in bulk cultures of murine T cells. In contrast, the lectin has been shown to stimulate purified B cells to leave G0, but not to proliferate. We demonstrate here that Con A induces comparable increases in intracellular Ca2+ levels in the two cell types. In B cells this appears to be due to Ca2+ influx. As expected, the lectin also provokes significant degradation of inositol phospholipids in T cells. However, it causes only minimal release of inositol phosphates in B cells. We therefore postulate that Con A may stimulate B cells by causing influx of Ca2+. In line with this, activation of B cells by the lectin is inhibited by cyclosporine, which preferentially affects stimulation of lymphocytes by Ca2+ mobilizing agents.