Identification of two subtypes of HLA‐DR2 by Southern blot analysis

We studied the polymorphism of HLA-DR2 by Southern blot analysis. Genomic DNA from 12 DR2 positive unrelated individuals was digested separately with five restriction endonucleases, Bam HI, Eco RI, Eco RV, Hind III and Pvu II. Hybridizing restriction fragments were visualized using radiolabeled beta-chain cDNA probes homologous to the DR and DQ subregions of the HLA. The results in the present study demonstrate that the two subtypes of DR2, DR2.1 and DR2.2, as defined by serological and cellular (PLT) techniques can be identified by Southern blot analysis. These two subtypes were identifiable after cleaving genomic DNA with Bam HI and EcoRV. DR2.1 correlated with restriction endonuclease fragments at 2.8 kb (DR beta) and 6.6 kb (DQ beta) after Bam HI digest, while DR2.2 correlated with a 2.9 kb (DR beta) and a 2.6 kb (DQ beta) restriction fragment after Eco RV digest. In addition, inheritance of the restriction fragment lengths defining DR2.1 and DR2.2 were observed in two families. In contrast, no differences between DR2.1 and DR2.2 were observed with the restriction enzymes Eco RI, Hind III and Pvu II.