GENETIC STUDIES ON THE MIXED LEUKOCYTE REACTION.

When leukocytes from pairs of unrelated human subjects are mixed and cultured for several days, blast-like cells appear that are capable of DNA synthesis and mitosis. This reaction can be estimated quantitatively by measuring the uptake of tritiated thymidine in the cultures. In experiments with 15 sibling pairs, the leukocytes of most individuals reacted less strongly with those of their siblings than with those of an unrelated subject.