Complexity of stimulation in MLC and the influence of matching for HLA-A and -B.

The influence of HLA-A and -B on primary mixed lymphocyte cultures (MLCs) was investigated in homozygous typing cell (HTC) experiments and by testing HLA-D/DR-identical, heterozygous individuals. Compatibility or identity for HLA-B between HLA-D-compatible or -identical responder and stimulator combinations resulted in lower MLC reactivity in many cases. Since this was especially true for haplotypes containing antigens with strong linkage disequilibrium, it was suggested that this observation was due to matching for antigens encoded by the B-D region rather than to matching for HLA-B itself. An additional influence of matching for HLA-A could not be demonstrated, possibly owing to the fact that stimulation caused by the HLA-A region is too weak to influence our results. The complexity of stimulation in MLC is discussed.