Immune rejection of tumor cells: in vivo significance of anti-tumor in vitro immune reactions.

The mechanism of immune tumor rejection remains poorly understood. The respective roles of antibodies, macrophages, cytolytic T cells (CTL) and that of "K" cells or any other cell which could be involved in antibody dependant cell mediated cytotoxicity are still unknown. It is probable that the CTL play some role in tumor rejection but the "in vivo" relevance of the other, "in vitro" detected phenomena, is less clear. The correlations between "in vivo" tumor rejection and "in vitro" detected reactions are very difficult to establish, specially for the following two reasons: a) the different methods used in vitro do not explore identical phenomena ; b) some of them provide both specific and non-specific reactions.