Cell-mediated suppression of tumor immunity has a non-specific component. I. Evidence from transplantation tests

Abstract

We have first demonstrated that the growth of a transplanted, 3‐methyl‐cholanthrene‐induced BALB/c sarcoma, MCA‐1425, in specifically immune syngeneic mice, was facilitated when the MCA‐1425 tumor cells were injected together with either a mixture of irradiated MCA‐1425 cells and thymus cells from mice immune to MCA‐1425 or a mixture of irradiated cells from an antigenically different BALB/c sarcoma, MCA‐1460, and thymus cells from mice immune to MCA‐1460. We then performed Winn assays to study the induction of an immune response that could prevent the outgrowth of MCA‐1425 cells in irradiated syngeneic recipients. Tumor immunity was found to be suppressed, if the mice immunized by a subcutaneous transplant of MCA‐1425 cells and used as lymphocyte donors, were injected intraperitoneally with cells from either a different sarcoma, MCA‐1460, or from 12‐day BALB/c embryos. We tentatively attribute our findings to antigen‐non‐specific suppressor effector cells and postulate that an antigen‐specific event is often involved in their induction.