Predictive value of HLA-DR matching for nonreactivity in mixed lymphocyte culture (MLC) depends on matching for HLA-D.

In white members of our panel who have been repeatedly typed, close association between the HLA-D and DR specificities was observed. The typings were concordant with both haplotypes in 71% of the North American white panel. In American Indians concordance was observed in 47%, and in American black panel members in only 24%. One-way MLC reactions between individuals matched for both HLA-DR and D were very low (15.8%). MLC reactions between individuals who were DR matched but D mismatched were found to be generally strong, with a mean DNV of 72.3%. It was concluded that the HLA-DR matching predicted the outcome of mixed lymphocyte culture reactions only when the individuals tested were matched also for HLA-D.