Immunogenicity, antigenicity and mechanisms of tumor rejection of mineral‐oil‐induced plasmacytomas in syngeneic BALB/c mice

Abstract

Abstract Transplantation immunity studies were conducted to determine whether mineral‐oil‐induced plasmacytomas of syngeneic BALB/c mice possess tumor‐associated transplantation antigens (TATAs). In a series of experiments to determine whether TATA could be detected, it was established that the optimum immunization regimen against TATA was obtained by immunizing syngeneic hosts with an intradermal inoculation of viable plasmacytoma cells, followed by therapeutic drug‐induced tumor regression with aniline mustard. This immunization regimen induced transplantation immunity not only to the homologous tumor employed for immunization, but was effective in demonstrating some cross‐protection when mice were rechallenged with other plasmacytomas. Thus, definite cross‐reactivity of antigens was observed between some plasmacytomas, but others shown to possess TATA did not share antigens. These, therefore, may possess distinct TATA (s). Further, studies with Winn assays employing cells from BALB/c mice immune to plasmacytoma cells support the idea that cell‐mediated immune functions are responsible for syngeneic plasmacytoma rejection. Specificity studies in subsequent Winn assays demonstrated that the kill was directed against plasmacytoma cells and not against TATA (s) of an MLV‐induced Moloney leukemia and SV40 virus‐induced tumor cells. The nature of the TATA (s) detected is not known, but they probably represent new “cell‐associated” antigens acquired during malignant transformation. Finally, the selective removal of the thymus‐dependent cell component of the immune lymphocyte population with anti‐theta serum and complement eliminated the tumor‐neutralizing properties of the immune cells in the Winn assay.