Induction of gp70-specific suppressor T-cells in mice inoculated with virus-producing tumor cells.

Inoculation of BALB/c mice with syngeneic, murine leukemia virus (MuLV)-producing (murine sarcoma virus-transformed) Balb/3T3 tumor cells resulted in diminution of alloreactivity as measured in the mixed leukocyte culture (MLC) reaction. Cells that suppressed this response were identified in the spleens of tumor-bearing mice 10--14 days after inoculation. The suppressor cells were adherent, radiosensitive T-lymphocytes of the Lyt 1-, 2, 3+ phenotype. Mice inoculated with Gross MuLV (G-MuLV)-producing tumor cells, but not those inoculated with a nonproducing subclone of the same tumor cells, developed suppressor T-cells. The T-cell-mediated suppression of the MLC could be augmented by the admixture of G-MuLV antigen, similar to that replicated by the tumor cell, but not by the admixture of a Rauscher-type MuLV antigen which lacked the cross-reactive, type-specific antigens of the G-MuLV. Furthermore, this augmented suppression could be abrogated by the addition of monoclonal anti-gp70 antibody. These findings indicated that antigen-specific suppressor T-cells were induced in response to leukemia virus antigen shed from and/or expressed on tumor cells and that the suppressive activity involved the specific recognition of the gp70 portion of the virus.