Lymphocyte-mediated cytolysis of allogeneic tumor cells in vitro: III. Enzyme sensitivity of target cell antigens

Abstract

Target tumor cells pretreated with high concentrations of papain or Pronase were resistant to lysis by cytotoxic T lymphocytes (CTL), whereas treatment with trypsin or neuraminidase had no protective effect. Parallel determinations of the H-2 content of target cells following enzyme treatment showed that approximately 80% of surface H-2 was removed by papain or Pronase, 40% by trypsin, and virtually none by neuraminidase treatment. Both susceptibility to lysis by CTL and content of surface H-2 after papain treatment were fully restored by 6 hr at 37 °C in nutrient medium. These findings suggest that lymphocyte-mediated cytolysis (LMC) determinants (target cell antigens bound by CTL) are sensitive to degradation by papain and Pronase but are resistant to the enzymatic action of trypsin and neuraminidase. That a similar pattern of enzyme sensitivity is shown by serologically defined H-2 antigens indicates that both functional classes, LMC and H-2, may have a structural association.