FIRST REPORT OF RECOMBINATION BETWEEN THE HLA-DR AND HLA-DQ LOCI WITHIN A FAMILY

Although unusual associations of HLA-DR and HLA-DQ alleles seen in anc estral haplotypes have indicated that recombination between these gene s occurred in the past, an actual crossover event between DR and DQ ha s never been shown within a family. In a study of families with Graves ' disease we have identified an individual from a three generation fam ily who inherited a maternal haplotype that is the result of a recombi national event between the HLA-DR and the HLA-DQ loci on her chromosom es. Family members were typed for HLA class I by the lymphocyte microc ytotoxicity test and for HLA class II by polymerase chain reaction (PC R) with sequence-specific primers or with sequence-specific oligonucle otide probes after PCR. Based on linkage disequilibrium it is likely t hat the recombinant haplotype is present in the proband rather than hi s brother. This haplotype was subsequently inherited by one of the pro band's sons. The data presented support the conclusion that the recomb inant haplotype resulted from a crossover event between the mother's D RB1 and DQA1 genes. Thus, recombination between the HLA-DR and HLA-DQ genes has been demonstrated within this family; a recombination event not previously described. (C) American Society for Histocompatibility and Immunogenetics, 1997. Published by Elsevier Science Inc.