Abrogation of tumor-inhibitory MRC-OX8+ (CD8+) effector T-cell generation in rats by selective depletion of neutrophils in vivo using a monoclonal antibody.

These studies were designed to examine the role of neutrophils in transplantation immunity to syngeneic rat tumors. We have earlier reported that specific transplantation immunity to syngeneic transplanted tumors is abrogated by selective depletion of peripheral-blood neutrophils by administration of a monoclonal antibody (MAb) (RP-3) at the time of immunization with X-irradiated tumor cells. In order to elucidate the mechanisms of this phenomenon, we have now examined whether induction of the sensitized spleen cells that inhibit the growth of tumor cells is inhibited by RP-3 treatment at the time of in vivo priming with tumor-associated antigen (TAA). Neutrophils were required to induce the sensitized T cells responsible for tumor inhibition with Winn's assay. In addition, CD8+ T cells are proved to be effector cells in an assay system of tumor-growth inhibition using a diffusion chamber. Our results indicate that neutrophils are required for priming rats with TAA to induce CD8+ effector T cells in tumor inhibition.