EFFECTOR AND SUPPRESSOR LYMPHOID-CELLS IN TUMOR-BEARING GUINEA-PIGS

The immune reaction of guinea pigs against their growing tumors was studied. Strain 13 guinea pigs were killed 2 wk after s.c. implantation of the transplantable methylcholanthrene-induced sarcoma (MC-D), when the tumor was 2-3 cm in diameter. Spleen, lymph node, bone-marrow and peripheral blood leukocytes (PBL), and subsets of spleen cells and PBL were mixed with lethal doses (105) of tumor cells and inoculated s.c. into normal recipients. Spleen, lymph node and bone-marrow cells enhanced or did not influence tumor growth, while PBL exerted a strong inhibitory effect. Normal spleen and normal PBL did not affect tumor growth. The spleen cells of tumor-bearing animals were separated on nylon wool columns. The 1st fraction containing T [thymus-derived] cells was responsible for tumor enhancement, the 2nd fraction containing predominantly non-T (Ia+) cells inhibited tumor growth. Adherent cells had no effect. After removal of T cells from the spleens with a specific rabbit antiserum or of non-T cells plus a minor portion of T cells with an anti-Ia serum (produced in strain 2 guinea pigs), the remaining cell population had, respectively, an inhibitory or an enhancing effect on tumor growth. Removal of T or Ia+ cells from PBL eliminated their anti-tumor effect. The major portion of splenic T cells formed EA [erythrocyte-antibody] rosettes. EA rosette-positive cells were restricted to a minor portion of peripheral T lymphocytes. Splenic and peripheral T cells from tumor-bearing animals were different functionally and according to their surface markers. Fc+ T cells may be suppressors which are triggered by immune complexes.