Non-oscillatory free Ca2+ response of single B cells and WEHI-231 cells after cross-linking of antigen receptors with anti-immunoglobulin.

Cross-linking of surface-immunoglobulin (sIg) has been associated with IP3 production and a rise in cytoplasmic-free calcium ([Ca2+]i) in studies of populations of normal and transformed B cells. We have examined the kinetics of the induced cytoplasmic calcium rises in single, Fura-2-loaded cells, during stimulation with a variety of agonists. Our data indicate that the responses of B cells to some stimuli, such as elevated cyclic AMP, consist of repetitive calcium transients, but these Ca2+ oscillations do not occur after sIg ligation. Rather, sIg cross-linking leads to a rapid rise in cytoplasmic calcium which is followed by a sustained elevation. Most of this response seems to result from an inflow of extracellular calcium rather than from internal stores.