title: Mode of action of a supernatant activity from T-cell cultures that nonspecifically stimulates the humoral immune response.
abstract: The mode of action of "allogeneic supernatant" (the culture supernatant of a 24-hr mixedlymphocyte reaction), has been studied. This factor stimulates the response of spleen cell cultures depleted in thymus-derived lymphoid cells (T-cells) to antigens that elicit a thymus-dependent response. We used a limiting dilution analysis, in which the frequency and size of response of individual bone-marrow-derived lymphoid cells (B-cells) could be measured. In confirmation of other reports, the occurrence of B-cells responding to antigen under different conditions was shown to follow a Poisson distribution in mouse spleen cell suspensions. Allogeneic supernatant increased responses to thymus-dependent antigens, both by increasing the frequency of B-cells whose response is initiated and by increasing the numbers of antibody-forming cells obtained from each responding B-cell. Two fractions were obtained by dialysis of the supernatant. The nondialyzable fraction contained factors able to increase both the frequency of B-cells responding to sheep erythrocytes, and the size of the responding unit. The dialysate contained factors that were only able to increase the numbers of antibody-forming cells obtained per responding B-cell from B-cells whose response had already been initiated by antigen-specific T-cells. Since the nondialyzable factors were active in the absence of detectable functional T-cells, it was concluded that these factors, produced by T-cells, might represent one mechanism whereby T-cells cooperate with B-cells in the initiation or development of a humoral immune response.
mesh_terms: D000818:Animals; D000917:Antibody Formation; D000942:Antigens, Bacterial; D001402:B-Lymphocytes / Q000276:immunology*; D002478:Cells, Cultured; D004912:Erythrocytes / Q000276:immunology; D004926:Escherichia coli / Q000276:immunology; D006462:Hemolytic Plaque Technique; D007959:Lymphocyte Culture Test, Mixed; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D008815:Mice, Inbred Strains; D012756:Sheep / Q000276:immunology; D013154:Spleen / Q000166:cytology / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000942:Antigens, Bacterial