Tumor-enhancing suppressor activator T cells in spleens and thymuses of tumor immune mice.

Abstract

Cells from spleens and thymuses of BALB/c mice whose Moloney sarcoma virus (MSV)-induced, primary sarcomas regressed 2-3 mo. earlier (MSV regressors) or were in the process of regressing could, when adoptively transferred to syngeneic mice given MSV at the age of 20 days, prevent natural regression of MSV sarcomas in recipient mice. Cells responsible for this tumor-enhancing effect expressed the Thy 1 marker. They were not demonstrable in thymuses of normal untreated mice or in mice that were immunized against or were bearing methylcholanthrene-induced sarcomas. Tumor-enhancing cells were not destroyed after administration of 400 rads (1 rad = 1.99 .times. 10-2 J/kg) of whole body radiation. The effect of irradiated cells was seen only in the presence of a nonirradiated T[thymus-derived]-cell population, represented in thymuses of normal control mice, with which they may interact. Studies on a transplantable, chemically induced, murine leukemia virus antigen-negative sarcoma, MCA-1460, further support the concept that relatively radioresistant thymus cells from immune mice can enhance tumor outgrowth by interacting with radiosensitive T cells present in nonimmune mice.