title: IgG subclass expression by human B lymphocytes and plasma cells: B lymphocytes precommitted to IgG subclass can be preferentially induced by polyclonal mitogens with T cell help.
abstract: The human IgG subclasses expressed by circulating B lymphocytes, tissue plasma cells, and plasma cells generated from B cell precursors in response to the polyclonal mitogens LPS and PWM were examined by immunofluorescence using subclass-specific monoclonal antibodies. The subclass distribution observed for circulating B lymphocytes was IgG2 (48%) greater than IgG1 (40%) greater than IgG3 (8%) greater than IgG4 (1%), while the distribution among IgG plasma cells in bone marrow, blood, spleen, and tonsils was IgG1 (64%) greater than IgG2 (26%) greater than IgG3 (8%) greater than IgG4 (1%). Multiple IgG isotypes were not observed on B cells or in plasma cells. Although IgG plasma cell responses to both LPS and PWM were T cell dependent, the distributions of IgG subclasses elicited were strikingly different. In control and LPS-stimulated cultures of blood mononuclear cells, the induced plasma cells expressed the IgG subclass distribution: IgG2 greater than 80%, IgG1 less than 20%, IgG3 less than 1%, IgG4 less than 1%. In PWM-stimulated cultures, the subclass distribution, IgG1 approximately 65%, IgG2 approximately 25%, IgG3 approximately 7%, IgG4 approximately 1%, was in perfect concordance with the in vivo subclass distribution of IgG plasma cells. Selective inhibition of suppressor T cell activity by x-irradiation and mitomycin C treatment did not alter the IgG subclass distribution pattern induced by LPS and PWM. Monoclonal antibodies were used to deplete selectively the B cell precursors bearing IgG1, IgG2, or IgG3 before PWM stimulation of blood mononuclear cells. In each instance, a reduction was observed only in the subpopulation of plasma cells producing the homologous IgG subclass. The results indicate that T cells can preferentially influence the terminal differentiation of B cells that are precommitted to different IgG subclasses.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology*; D005455:Fluorescent Antibody Technique; D006412:Hematopoietic Stem Cells / Q000276:immunology; D006801:Humans; D007074:Immunoglobulin G / Q000032:analysis / Q000145:classification / Q000276:immunology*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008213:Lymphocyte Activation; D008212:Lymphocyte Depletion; D051379:Mice; D008934:Mitogens / Q000494:pharmacology; D010950:Plasma Cells / Q000276:immunology*; D011043:Pokeweed Mitogens / Q000494:pharmacology; D013601:T-Lymphocytes / Q000276:immunology / Q000528:radiation effects; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D007074:Immunoglobulin G; D008070:Lipopolysaccharides; D008934:Mitogens; D011043:Pokeweed Mitogens