Comparative Studies on the Mechanisms of Nonspecific, Con A-Dependent Cytolysis and Specific T Cell-Mediated Cytolysis

Abstract

Several groups have shown that lymphocyte populations rich in previously differentiated, alloimmune cytolytic T cells nonspecifically lyse syngeneic tumor target cells in the presence of concanavalin A (Con A). We have carried out studies comparing the mechanism of this nonspecific, Con A-dependent cytolysis to that of specific T cell-mediated cytolysis of allogeneic targets. Nonspecific, Con A-dependent cytolysis was experimentally resolved into three successive steps — adhesion formation, programming for lysis, and killer cell-independent lysis — by use of techniques previously developed for studying these steps in specific T cell-mediated cytolysis. The formation of nonspecific, Con A-dependent adhesions proceeded more slowly and was more temperature sensitive than specific adhesion formation. Mg⁺⁺ in the absence of appreciable Ca⁺⁺ was sufficient to support optimal adhesion formation in both systems. The kinetics of programming for lysis at 37°C were similar in the two systems; however nonspecific, Con A-dependent programming for lysis was approximately 2- to 3-fold more temperature sensitive than specific programming for lysis in the temperature range 37 to 22°C. Programming for lysis was strongly Ca⁺⁺ dependent in both systems. Nonspecific programming for lysis occurred within 20 min after the application of Con A, suggesting that Con A causes the expression of a preformed cytolytic mechanism, and that no Con A-induced differentiation is necessary. A number of known inhibitors of specific T cell-mediated cytolysis including cytochalasin B, DMSO, lidocaine, dibutyryl cyclic AMP, and colchicine were found also to inhibit nonspecific, Con A-dependent cytolysis. Thus, Con A does not bypass any steps inhibited by these agents. Antibody to target cell H-2 inhibited specific cytolysis but not nonspecific, Con A-dependent cytolysis. Overall, the results are compatible with the hypothesis that cytolysis in these two systems proceeds via similar mechanisms.