Helper and suppressor functions of panned populations of immune peritoneal T cells with reactivity to the rat mammary adenocarcinoma 13762A

The phenotype of glass-adherence-depleted tumor-immune peritoneal exudate lymphocytes (PEL) which generated anti-tumor reactivity against the rat mammary adenocarcinoma 13762A in vitro was examined by indirect panning. Monoclonal antibodies W3/25 and OX8, directed against the CD4 and CD8 differentiation antigens, respectively, were used to separate immune PEL into subsets of functionally different T cells. The panned populations of immune PEL were examined for anti-tumor reactivity in three different in vitro assays. Tumor-specific proliferation, tumor-specific induction of the helper lymphokine interleukin 2 (IL-2), and tumor-specific induction of an antiproliferative tumor-induced suppressor lymphokine (TISL) were determined. Panning experiments together with indirect immunofluorescence analysis of unpanned immune PEL indirectly indicated that a proportion of cells (15-20%) coexpressed CD4 and CD8 antigens. Strong tumor-specific proliferation and IL-2 and TISL production were generated from these double-positive cells, as determined by double-panning experiments. Significant tumor-specific proliferation and IL-2 production were produced also from CD4⁺CD8^- cells, but TISL production was minimal, and could be accounted for by contaminating CD4⁺CD8⁺ cells. CD4^-CD8⁺ cells produced negligible responses against the tumors as measured by these three assays, and no synergistic responses were demonstrated when CD4^-CD8⁺ cells were incubated together with CD4⁺CD8^- cells. These data demonstrated that CD4⁺CD8⁺ T cells exist in primed populations of rat peripheral lymphocytes, and that both helper and suppressor functions were generated from these double-positive cells.