Susceptibility to insulin-dependent diabetes defined by restriction enzyme polymorphism of HLA-D region genomic DNA.

DNA fragments complementary to cloned sequences encoding HLA-D region class II antigen alpha- and beta-chains were determined by genomic blotting with DNA from HLA-typed members of 22 complete families, 12 of which had a proband with insulin-dependent diabetes mellitus (IDDM). Analysis of genotypes showed that the DNA sequences were linked to HLA-DR and permitted confirmation of recombinations in two families. Digestion with the restriction enzymes BamHI, EcoRI, and PstI and hybridization with an HLA-D region beta-chain cDNA probe confirmed a BamHI 3.7 kilobase (kb) fragment present at low frequency among diabetic individuals and a BamHI 3.2 kb fragment that was also decreased among the diabetic subjects compared with siblings (P less than 0.05) as well as nonrelated control siblings (P less than 0.02) and their parents (P less than 0.01). BamHI 12.0 kb (P less than 0.05) and 5.8 kb (P less than 0.02, P less than 0.02), EcoRI 20 kb (P less than 0.05, P less than 0.02), and PstI 6.0 kb (P less than 0.05) fragments were more frequent in diabetic individuals compared with nonrelated control siblings or their parents, respectively. Analysis of individual haplotypes revealed that HLA-DR4-containing chromosomes were heterogeneous among controls but that the diabetic individuals showed a similar pattern of restriction fragment length polymorphism. Genomic blotting of blood lymphocyte DNA with a cDNA clone encoding the chain of HLA-D region class II antigens permits detection of fragments that are strongly associated with IDDM.