Cell-mediated immunity against malignant melanoma in monozygous twins.

brought new methods of leukocyte and tissue typing. The MLC2 reaction (3) allows the reproduction in vitro of the reaction of transplantation immunity in vivo (1) by the selective measurement of antigenic incompatibilities for the important transplantation antigens. Specific tumor cell antigens are known to be weaker than transplantation antigens. We undertook a program to determine if MLC is capable of detecting these weaker “foreign― antigens by blastoid transformation of autologous lymphocytes. The observation of the simultaneous occurrence of malignant melanoma of the skin in monozy gous brothers of a set of triplets who are reported elsewhere in detail (25) provided us with a unique experimental model with which to study this question.