title: Suppression of tumor-specific cell-mediated cytotoxicity by immunoregulatory alpha-globulin and by immunoregulatory alpha-globulin-like peptides from cancer patients.
abstract: The suppression of tumor-specific cell-mediated cytotoxicity by human immunoregulatory alpha-globulin (IRA), by a peptide fraction derived from IRA, and by IRA-like peptides from the serum of cancer patients was studied in a syngeneic murine tumor-host system. Splenic lymphocytes from tumor-immunized mice were cytotoxic specific tumor cells in vitro as measured by the [125]-iododeoxyuridine release microcytotoxicity assay. However, this effect was significantly depressed if 1.25 to 5 mg of IRA per ml were added to the cultures. Pooled lyophilized normal human serum protein was inactive. IRA peptide and IRA-like peptide fractions from cancer patients were also highly suppressive of cell-mediated cytotoxicity at much lower concentrations (0.05 to 0.5 mg/ml). Control human serum peptide, which failed to inhibit the induction of hemolytic plaque-forming cells in sheep erythrocyte-injected mice, had no effect on cell-mediated cytotoxicity. IRA and IRA-like peptide fractions were not cytotoxic to the effector lymphocytes or to the target cells at the concentrations used.
mesh_terms: D000510:Alpha-Globulins / Q000276:immunology* / Q000494:pharmacology; D000818:Animals; D000951:Antigens, Neoplasm; D003601:Cytotoxicity Tests, Immunologic; D005260:Female; D006462:Hemolytic Plaque Technique; D006801:Humans; D007111:Immunity, Cellular; D007165:Immunosuppression Therapy; D066298:In Vitro Techniques; D051379:Mice; D008809:Mice, Inbred C3H; D009369:Neoplasms / Q000276:immunology*; D010455:Peptides / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology
chemical_list: D000510:Alpha-Globulins; D000951:Antigens, Neoplasm; D010455:Peptides