title: Antigen-specific purification of blocking factors from sera of mice with chemically induced tumors.
abstract: Serum from mice with growing tumors can prevent ("block") the destruction of tumor cells by immune lymphocytes, as measured in a microcytotoxicity assay. Factors responsible for this blocking activity were purified by binding to immune adsorbents that had been prepared from antibodies obtained by immunizing BALB/c mice to the homologous tumors. Two transplantable BALB/c sarcoma lines with individually different tumor-specific transplantation antigens were studied in parallel. The original tumor-specific blocking activity was recovered by elution of the immune adsorbents; that is, (i) eluates blocked the reduction of surviving tumor cell targets by immune lymphocytes only if the tumor specificity, and (ii) immune adsorbent columns prepared from tumor-immune sera recognized the purified blocking fractions in a tumor-specific fashion, indicating that a portion of the humoral response in the immune mice was directed against a factor that was individually distinct for each tumor. Absorption of eluates with the homologous tumor cells removed their blocking activity, indicating that the blocking factors have antigen-binding properties. Blocking activity in the purified fractions resided in molecules presumptively identified as glycoproteins by affinity chromatography on concanavalin A-Sepharose.
mesh_terms: D000818:Animals; D000951:Antigens, Neoplasm; D002846:Chromatography, Affinity; D003208:Concanavalin A / Q000378:metabolism; D003602:Cytotoxicity, Immunologic; D000939:Epitopes; D006023:Glycoproteins / Q000302:isolation & purification*; D007104:Immune Adherence Reaction; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008970:Molecular Weight; D009374:Neoplasms, Experimental / Q000276:immunology*
chemical_list: D000951:Antigens, Neoplasm; D000939:Epitopes; D006023:Glycoproteins; C020163:blocking factor; D003208:Concanavalin A