Level of mIa expression on mitogen-stimulated murine B lymphocytes is dependent on position in cell cycle.
Using correlated flow cytometric analysis of cell surface Ia antigen expression (immunofluorescence) and cell cycle phase (pulse-width of axial light extinction), we have quantitated changes in expression of mIa antigen on murine B cells during progression through cell cycle. Our results indicate that density of mIa expressed on mitogen-stimulated B cells increases fourfold to fivefold during the transition from G0 to G1. By early S phase, mIa density has decreased by fourfold to fivefold relative to peak expression. This decrease becomes more evident by late S, G2, and M phases, when an eightfold decrease in mIa antigen density is observed relative to peak levels. This decrease results in mIa antigen expression lower than that of resting, unstimulated B cells. Therefore, maximum mIa antigen expression occurs during G0 to G1 transition and in early G1, when a requirement for I region-restricted, antigen-driven T cell help for thymus-dependent, antigen-driven B cell activation has been demonstrated.
D000818:Animals; D000954:Antigens, Surface / Q000032:analysis*; D001402:B-Lymphocytes / Q000166:cytology* / Q000276:immunology; D002453:Cell Cycle / Q000187:drug effects; D003609:Dactinomycin / Q000494:pharmacology; D005434:Flow Cytometry; D000949:Histocompatibility Antigens Class II / Q000032:analysis*; D006918:Hydroxyurea / Q000494:pharmacology; D007399:Interphase / Q000187:drug effects; D008070:Lipopolysaccharides / Q000494:pharmacology; D008213:Lymphocyte Activation; D051379:Mice; D008807:Mice, Inbred BALB C; D014747:Vinblastine / Q000494:pharmacology
D000954:Antigens, Surface; D000949:Histocompatibility Antigens Class II; D008070:Lipopolysaccharides; D003609:Dactinomycin; D014747:Vinblastine; D006918:Hydroxyurea