Mixed lymphocyte reactivity against normal cells by splenic lymphocytes from tumor-bearing mice : I. Studies of vigorous immune responsiveness induced in f(1) mice by parental strain tumor cells.

The establishment of an intimate connection between autoimmunity and neoplasia would require the demonstration of an experimentally induced, tumor-dependent autoimmune process. For this reason, we have studied cellular immune reactions of mice bearing a transplantable leukemia (L1210). Spleen cells from hybrid BDF(1) mice bearing the L1210 tumor (BDFt) reacted vigorously in mixed lymphocyte culture with mitomycin-treated, normal spleen cells from mice of the parental strain from which the L1210 tumor was derived (DBA/2). Spleen cells from nontumor-bearing BDF(1) mice reacted only weakly with these parental cells. The BDFt cells likewise did not respond when cultured with mitomycin-treated spleen cells from the other parental strain (C57B1/6). The vigorous mixed lymphocyte reaction (MLR) by BDFt cells against normal parental cells of the same strain as the tumor was not due to a double exposure of the reacting cells to histocompatibility antigens shared by tumor cells and normal parental cells. The response of cells from tumor-bearing F(1) mice against normal parental cells seen in these experiments suggests the possibility of the induction of an autoimmune-like process against host lymphocytes by spleen cells from leukemic mice. Theoretically such a phenomenon would considerably reduce an animal's ability to mount an immune attack against malignant cells.

Mixed lymphocyte reactivity against normal cells by splenic lymphocytes from tumor-bearing mice : ii. Studies of autoimmune-like activity in completely syngeneic and semisyngeneic systems.

A possible consequence of an antilymphocytic autoimmune process would be serious impairment of an animal's ability to destroy tumor cells. One measure of autoimmune reactivity of this type would be the demonstration of cellular immune responsiveness by cells from tumor-bearing mice against syngeneic normal cells. These experiments demonstrate that spleen cells from mice bearing a lymphocytic leukemia of identical histocompatability type as the host mounted a vigorous immune response against normal syngeneic cells in a mixed lymphocyte reaction (MLR). Moreover, ascitic cells from leukemic mice responded significantly to normal syngeneic spleen cells in MLR's. The former reactions are usually much more vigorous than the responses of normal to malignant cells. These results are discussed in terms of the relationship between autoimmunity and neoplasia. Alternative explanations necessitated by the dangers involved in the interpretation of the immunology of transplantable tumors are considered.