title: Depressed antibody responses to a thymus-dependent antigen in toxoplasmosis.
abstract: The immunodepressive effect of Toxoplasma gondii infection in mice was studied, using sheep erythrocytes (SRBC) as the testing antigen and serum hemagglutinins, hemolysins, and both direct and indirect splenic plaque-forming cells (PFC) to SRBC as assays. In the primary antibody response, immunoglobulin M (IgM), hemagglutinins, and hemolysins and both IgM- and IgG-secreting PFC were depressed in animals immunized after infection. Maximum immunodepression occurred during the first 3 weeks of Toxoplasma infection. When the secondary antibody response was studied, results varied. Mice immunized with SRBC after being infected with T. gondii had a depression in both IgM and IgG PFC. Mice immunized with SRBC before being infected with T. gondii and then given a challenge dose of SRBC had a delay, but no an actual depression, in IgG hemagglutinins and hemolysins and IgG-secreting PFC. These studies show that the immunodepression associated with Toxoplasma infection is complicated, and they provide no definitive explanation for the mechanism.
mesh_terms: D000818:Animals; D000917:Antibody Formation; D000937:Antigen-Antibody Reactions; D006388:Hemagglutinins / Q000032:analysis; D006460:Hemolysin Proteins / Q000032:analysis; D006462:Hemolytic Plaque Technique; D007156:Immunologic Memory; D007165:Immunosuppression Therapy; D008297:Male; D051379:Mice; D013950:Thymus Gland / Q000276:immunology*; D014122:Toxoplasma / Q000276:immunology*; D014123:Toxoplasmosis / Q000276:immunology*
chemical_list: D006388:Hemagglutinins; D006460:Hemolysin Proteins