Persistent calcium elevation correlates with the induction of surface immunoglobulin-mediated B cell DNA synthesis.
Surface immunoglobulin (sIg)-mediated stimulation of B lymphocytes induces a tyrosine kinase-dependent sequence of events leading to rapid and 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 show by digital image analysis of single B cells that conditions which lead to B cell proliferation are associated with low-level but persistent sustained or cyclic elevations in [Ca2+]i. In marked contrast, early and nonsustained elevations in [Ca2+]i are induced in B cells by stimuli that lead to G1 transition but fail to progress to DNA synthesis. Thus, when B cells were stimulated with mitogenic and nonmitogenic anti-IgD antibodies, both of which induce entry of cells into G1 and early calcium transients of comparable magnitude, persistent low-level calcium elevations were only detected in cells stimulated with the mitogenic antibody. Furthermore, persistent calcium elevations were also seen when B cells were stimulated with a multivalent dextran-anti-Ig conjugate which induced very high levels of B cell proliferation in the absence of detectable phosphatidylinositol 4,5-biphosphate hydrolysis or elevations in [Ca2+]i as detected by flow cytometry. Finally, B cells from X-linked B cell-defective mice, which do not proliferate in response to anti-Ig antibody, show marked and early increases in [Ca2+]i, but do not show persistent calcium elevations. These data suggest that the rapid and large increases of [Ca2+]i seen in lymphocytes within seconds after antigen receptor ligation may be associated with entry in G1, whereas low-level but persistent elevations may be the hallmark of a cell destined to synthesize DNA.
Yamada
H
H
Immune Cell Biology Program, Naval Medical Research Institute, Bethesda, Maryland 20889-5055.
June
C H
CH
Finkelman
F
F
Brunswick
M
M
Ring
M S
MS
Lees
A
A
Mond
J J
JJ
D000818:Animals; D000888:Antibodies, Anti-Idiotypic / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D004247:DNA / Q000096:biosynthesis*; D008213:Lymphocyte Activation; D051379:Mice; D008811:Mice, Inbred DBA; D011947:Receptors, Antigen, B-Cell / Q000502:physiology*
D000888:Antibodies, Anti-Idiotypic; D011947:Receptors, Antigen, B-Cell; C039951:anti-IgD; D004247:DNA; D002118:Calcium