HISTOCOMPATIBILITY ANTIGENS CAUSING STIMULATION IN MIXED LYMPHOCYTE CULTURE INTERACTIONS ANTIGENIC IDENTITY OR SIMILARITY BETWEEN INDIVIDUALS

Abstract

Specific eliminations of human histocompatibility antigen-reactive cells were accomplished by incubating mixed lymphocyte cultures initially with ³H-thymidine of high specific activity. The cells remaining after hot pulse treatment were stimulated by various allogeneic cells. Responding cells were insensitive to restimulation by the original cell donor. On the other hand, the response with secondary stimulation by other cell donors was dependent upon the HL-A and mixed lymphocyte culture (MLC) relationship between the initial and restimulating cell donor. If they were HL-A-identical siblings, no restimulation response was observed. If they were HL-A-incompatible unrelated subjects, a positive response was elicited which, in most cases, was comparable to control values. However, if they were HL-A-identical unrelated subjects, a reduced secondary stimulation response was almost always seen, and the amount of reduction was, in turn, dependent upon the MLC responses between the initial and restimulating cell donors in combinations with each other. The results indicate that sharing or similarity of histocompatibility antigens important for MLC stimulation occurs more often in HL-A-identical unrelated persons than in randomly selected subjects. Nonrandom association between HL-A and MLC loci products could be an explanation for this observation.