title: In vitro plaque-forming cell responses induced by Streptococcus pneumoniae in humans.
abstract: When peripheral blood lymphocytes (PBL) were stimulated in vitro with the rough form of type 2 Streptococcus pneumoniae R36a, the resulting plaque-forming cells (PFC) did not produce antibodies directed against phosphorylcholine, a major antigenic determinant of the cell wall C-polysaccharide. Instead, R36a stimulated polyclonal PFC in PBL and splenic lymphocytes. We compared the polyclonal responses stimulated by R36a with those induced by two well-characterized polyclonal activators (PA), Staphylococcus aureus Cowan I and pokeweed mitogen (PWM). We found that R36a was a poor mitogen for PBL, whereas the other two PA were potent mitogens; that the predominant isotype produced in response to all three PA was IgM; that adherent cells strongly inhibited the polyclonal PFC response to both R36a and Staph. aureus but not PWM; and that T cells were necessary for induction of polyclonal antibody-secreting cells by all three stimuli.
mesh_terms: D000328:Adult; D000907:Antibodies, Bacterial / Q000096:biosynthesis*; D000921:Antibody-Producing Cells / Q000276:immunology*; D004247:DNA / Q000096:biosynthesis; D006462:Hemolytic Plaque Technique; D006801:Humans; D007143:Immunoglobulin Heavy Chains / Q000096:biosynthesis; D008213:Lymphocyte Activation; D009000:Monocytes / Q000276:immunology; D011043:Pokeweed Mitogens / Q000494:pharmacology; D011135:Polysaccharides, Bacterial / Q000276:immunology; D013211:Staphylococcus aureus / Q000276:immunology; D013296:Streptococcus pneumoniae / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology; D000511:alpha-Macroglobulins / Q000276:immunology
chemical_list: D000907:Antibodies, Bacterial; D007143:Immunoglobulin Heavy Chains; D011043:Pokeweed Mitogens; D011135:Polysaccharides, Bacterial; D000511:alpha-Macroglobulins; C032306:polyclonal B cell activator; C027158:polysaccharide C-substance (Streptococcus); D004247:DNA