Tumor-mediated immunosuppression: Prevention by inhibitors of prostaglandin synthesis

Abstract

The addition of MC16 tumor cells (a prostaglandin E 2-producing cell line induced in C57B1/6J mice by methylcholanthrene) to cultures of normal syngeneic spleen cells inhibits the antibody response of these cells to sheep red blood cells. This inhibition can be blocked by adding to the cultures prostaglandin synthetase inhibitors, such as indomethacin, flufenamic acid and aspirin. These MC16 tumor cells are also immunosuppressive in vivo . Mice bearing the syngeneic MC16 tumor become unresponsive to sheep red blood cells as the tumor grows. As in the in vitro test system, inhibitors of prostaglandin synthetases seem to block the immunosuppressive activity of MC16 cells in vivo since tumor-bearing mice, treated therapeutically with indomethacin, responded normally in their production of antibody to sheep red blood cells.