Crosslinking by ligands to surface immunoglobulin triggers mobilization of intracellular ⁴⁵Ca²⁺ in B lymphocytes

Detailed studies of steady-state ion fluxes in murine lymphocytes were used to examine for possible ionic changes generated by surface Ig, the antigen receptor of B lymphocytes. When bound by ligands, surface Ig triggered the mobilization and release of ⁴⁵Ca²⁺ from the cell interior by a transmembrane process requiring crosslinking of the bound receptors. This ionic event was unique for two reasons: it did not occur when other common lymphocyte surface macromolecules were bound with rabbit anti-lymphocyte antibodies; and it was not accompanied by a general perturbation of lymphocyte ionic properties such as a change in ⁴²K⁺ fluxes nor did it depend on the presence of extracellular ions. Capping of surface Ig shares the same time sequence, dose response, requirement for crosslinking, and lack of dependence on extracellular ions. These correlations suggest that mobilization of intracellular Ca²⁺ may represent an early ionic signal for the contractile activation of lymphocytes that generates capping of surface Ig.