RFLP of the HLA-DQα region: a diallelic DXα polymorphism, not linked to DR and DQ specificities

Abstract

HLA-DQ.alpha.DNA polymorphism was studied by Southern blot analysis in a panel of 117 individuals, consisting of 56 randomly selected and 61 HLA-DR homozygous individuals. Hybridizing fragments representing DQ.alpha. genes correlate with DR specificities owing to linkage disequilibrium between DQ and Dr. Two fragments representing DX.alpha. genes were identified with the restriction enzymes PvuLL and TaqI and a DQ.alpha. cDNA probe. The two fragments of PvuII-DQ.alpha. hybridization (a 7200 and a 7000 basepair fragment) and the two of TaqI-DQ.alpha. (2200 and 1900 basepairs) have an identical distribution in the panel, and reveal gene frequencies of 49.1% and 50.9%; they behave as alleles of the putative DX.ALPHA. locus. The panel study shows that the DX.alpha. fragments are not linked with the DR or DQ specificites but segregate along with HLA as shown in family studies.