Cellular natural killing against thymocytes.

Cell-mediated immunity in vivo results in allograft destruction, in graft versus host reactions following bone marrow transplantation, in delayed type hypersensitivity responses to mycobacteria and other antigens, in autoimmune or autoaggressive diseases and in immunity to tumors, allogeneic or syngeneic.1.2 Natural cellular immunity-also known as cellular natural killing (CNK)-has been described recently in man-5 and in mice." The possible role of both CNK and cell-mediated immunity through "sensitization" process is one of the current topics in both clinical and basic immunology. Especially, the nature of target cells in relation to CNK is presently subject to extensive research. In the previous paper, we first demonstrated CNK against 'normal' cells, using human thymocytes as target cells.10 In this article we studied CNK against human thymocytes more in detail from the aspect of individual difference in CNK activity. CNK against autologous and xenogeneic thymoc yytes was also examined in addition to cytotoxicity against allogeneic thymocytes.