PERSISTENT CALCIUM ELEVATION CORRELATES WITH THE INDUCTION OF SURFACEIMMUNOGLOBULIN-MEDIATED B-CELL DNA-SYNTHESIS

Surface immunoglobulin (sIg)-mediated stimulation of B lymphocytes ind uces a tyrosine kinase-dependent sequence of events leading to rapid a nd large elevations in intracellular ionized calcium ([Ca2+]i). These early biochemical events do not necessarily lead to proliferation of B cells, however, and conversely, the absence of or inhibition of these events does not necessarily prevent cellular proliferation. We now sh ow by digital image analysis of single B cells that conditions which l ead to B cell proliferation are associated with low-level but persiste nt sustained or cyclic elevations in [Ca2+]i. In marked contrast, earl y and nonsustained elevations in [Ca2+]i are induced in B cells by sti muli that lead to G1 transition but fail to progress to DNA synthesis. Thus, when B cells were stimulated with mitogenic and nonmitogenic an ti-IgD antibodies, both of which induce entry of cells into G1 and ear ly calcium transients of comparable magnitude, persistent low-level ca lcium elevations were only detected in cells stimulated with the mitog enic antibody. Furthermore, persistent calcium elevations were also se en when B cells were stimulated with a multivalent dextran-anti-Ig con jugate which induced very high levels of B cell proliferation in the a bsence of detectable phosphatidylinositol 4,5-biphosphate hydrolysis o r elevations in [Ca2+]i as detected by flow cytometry. Finally, B cell s from X-linked B cell-defective mice, which do not proliferate in res ponse to anti-Ig antibody, show marked and early increases in [Ca2+]i, but do not show persistent calcium elevations. These data suggest tha t the rapid and large increases of [Ca2+]i seen in lymphocytes within seconds after antigen receptor ligation may be associated with entry i n G1, whereas low-level but persistent elevations may be the hallmark of a cell destined to synthesize DNA.