title: Control of cell cycle entry and progression in mitogen-stimulated human B lymphocytes.
abstract: Tonsillar B lymphocytes were stimulated to proliferate by the mitogenic combination of phorbol dibutyrate and ionomycin. Progression through the cell cycle was monitored by measurements of cellular DNA and RNA content using flow cytometry. Changes in surface expression of class II MHC antigens and CD20 antigen were also monitored as early parameters of B lymphocyte activation and cell cycle progression. The results showed that about 60% of the population synchronously entered and progressed through the cell cycle. The transition from the resting state, signaled by increased RNA content, occurred about 12 to 24 hr after stimulation; S phase entry occurred at about 36 hr. Small, variable populations of cells appeared to be unresponsive to the stimuli, either because they were "preactivated" before in vitro stimulation or were already dying. The kinetics of appearance and accumulation of several cell cycle regulated/regulatory proteins were followed by immunoblotting. The proliferating cell nuclear antigen (PCNA) cyclin A and p33cdk2 proteins were either absent or present in very low amounts in resting cells and first became detectable in increased amount beginning at about 24 hr after stimulation; increased p34cdc2 protein was not detected until about 36 hr. Increased cellular content and phosphorylation of the p110Rb protein was already obvious by 24 hr after stimulation. The effects of several immunosuppressive agents were examined using purified B cells. Both cyclosporin A and an FK506 analogue were shown to inhibit proliferation of B lymphocytes, at the low doses also inhibitory to T cells.
authors.affiliation: Department of Pediatrics, National Jewish Center for Immunology and Respiratory Medicine, Denver, Colorado 80206.
authors.forename: K
authors.initials: K
authors.lastname: Takase
authors.forename: N
authors.initials: N
authors.lastname: Terada
authors.forename: J J
authors.initials: JJ
authors.lastname: Lucas
authors.forename: E W
authors.initials: EW
authors.lastname: Gelfand
mesh_terms: D015703:Antigens, CD / Q000096:biosynthesis; D018951:Antigens, CD20; D000944:Antigens, Differentiation, B-Lymphocyte / Q000096:biosynthesis; D001402:B-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D016203:CDC2 Protein Kinase / Q000096:biosynthesis / Q000378:metabolism; D042846:CDC2-CDC28 Kinases; D002453:Cell Cycle; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases / Q000096:biosynthesis / Q000378:metabolism; D016213:Cyclins / Q000096:biosynthesis; D006684:HLA-DR Antigens / Q000096:biosynthesis; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology; D015759:Ionomycin / Q000494:pharmacology; D008213:Lymphocyte Activation; D008934:Mitogens / Q000494:pharmacology*; D014066:Palatine Tonsil / Q000166:cytology; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D010766:Phosphorylation; D018809:Proliferating Cell Nuclear Antigen / Q000096:biosynthesis; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000378:metabolism
chemical_list: D015703:Antigens, CD; D018951:Antigens, CD20; D000944:Antigens, Differentiation, B-Lymphocyte; D016213:Cyclins; D006684:HLA-DR Antigens; D007166:Immunosuppressive Agents; D008934:Mitogens; D018809:Proliferating Cell Nuclear Antigen; D016160:Retinoblastoma Protein; D015240:Phorbol 12,13-Dibutyrate; D015759:Ionomycin; D017346:Protein Serine-Threonine Kinases; D016203:CDC2 Protein Kinase; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases