Recombination within the HLA-D region. Correlation of molecular genotyping with functional data.

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Abstract
Molecular genotyping of the HLA-D/DR region in a family correlated with serologic and cellular typing data. It was further possible to predict a subtle difference in SB region-related functions from such molecular studies. A family that included an individual who inherited an HLA haplotype with a paternal recombination between HLA-B and the HLA-D/DR region was identified by classic HLA typing techniques. Segregation of HLA-D/DR region genes in this family was studied by Southern blot analysis using cDNA [complementary DNA] probes for DR.alpha., DR.beta., DC.alpha., DC.beta. and SB.beta.. Restriction enzyme fragment polymorphisms observed for every gene tested were in concordance with assigned HLA haplotypes (including the individual known to have inherited a paternal recombinant haplotype) with 1 exception: 2 HLA identical siblings were obsreved to have different SB.beta. restriction fragment patterns. Further testing revealed that 1 individual inherited a maternal HLA haplotype recombinant between the HLA-D/DR region and SB.beta.. Although both maternal SB alleles typed as SB4, allelic differences could be detected cellularly by primed lymphocytes and by the differential expression of a class II cell surface antigen using monoclonal antibody. Therefore, predicted and nonpredicted recombinant haplotypes were detected in a family by molecular genotyping.