title: An immunoregulatory factor associated with spleen cells from tumor-bearing animals. III. Characterization of the factor's target cells.
abstract: An immunoregulatory factor associated with spleen cells from tumor-bearing mice was found to potentiate the generation of antibody-producing cells (APC). In an attempt to characterize the target cell of this enhancing factor (EF), its activity in mice devoid of mature T lymphocytes was tested. Levels of anti-SRBC APC were augmented when EF was injected together with SRBC to nude mice and "B" mice. In addition, EF potentiated the antibody response against the IgM-inducing T-independent pneumococcal plysacchardide SIII antigen. These results suggest that EF most probably exerts its enhancing influence directly on B lymphocytes. In a different line of experiments adoptive secondary responses were performed. Mice were immunized with SRBC as carrier or with the NIP-chicken erythrocytes (as a source of NIP-specific primed B cells) in the presence or absence of EF. Various combinations of spleen cells from the donor immunized mice were transferred in a mixture with NIP-SRBC to lethally irradiated recipient mice, EF did not exert any potentiation effect on helper function, except when primed B cells were used. In contrast, a clear activation or clone expansion of hapten-specific B cells was observed. These findings indicate that the enhancing factor from tumor-bearing animals directly affected the antigenic triggering of B lymphocytes and their subsequent proliferation and differentiation to antibody-producing cells.
mesh_terms: D000818:Animals; D000917:Antibody Formation; D000921:Antibody-Producing Cells / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology*; D004912:Erythrocytes / Q000276:immunology; D006241:Haptens; D006462:Hemolytic Plaque Technique; D008175:Lung Neoplasms / Q000276:immunology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008819:Mice, Nude; D009374:Neoplasms, Experimental / Q000276:immunology*; D013154:Spleen / Q000166:cytology / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology; D013934:Thymectomy
chemical_list: D006241:Haptens