| Abstract: | In comparison to control animals the natural killer (NK) efficiency of spleen and blood lymphocyte population was reduced in three systems of tumor-bearing animals: transplanted methylcholanthrene (MC) and primary Moloney sarcoma virus (MSV) induced sarcomas in CBA mice, and athymic “nude” mice carrying grafts of human lymphoblastoid cell lines. No evidence for suppressor cells was found. After regression of the MSV tumors the activity was high again. The effect was measured on YAC - a culture line of a Moloney leukemia virus-induced lymphoma in an A mouse - which is highly sensitive to the NK effect. Against another lymphoma, RBL-5, (Rauscher leukemia virus induced in C57BL mice), the effect of control spleen cells was low while that of the MSV tumor-bearing spleen cells was high, indicative of immunization effect. With regard to the virus-induced antigens, YAC and RBL-5 cross-react. Analysis of the NK effector population indicated that anti-YAC killer cells are enriched after passage through nylon wool. This would indicate a cytotoxic role of T cells. However, treatment with anti-RBL-l.2 serum did not markedly influence the effect. On the other hand, anti-RBL-5 activity of spleens from tumor-bearing (CBA × C57BL)F1 mice decreased after removal of Thy-1.2-positive cells. YAC thus seems to be more sensitive to the NK effect, while RBL-5 to the T cell-mediated immune effect. Cytotoxic lymphocytes for YAC and RBL-5 could be isolated from MSV tumors of CBA but not of A mice in spite of the regularly occurring regression also in the latter strain. |
