HLA‐D Region RFLPs Indicate That Susceptibility to Insulin‐dependent Diabetes in South India is Located in the HLA‐DQ Region

Abstract

Recently close markers for insulin‐dependent diabetes mellitus in Western ‘Caucasoid’ subjects have been defined from DQ region (both α and β genes) restriction fragment length polymorphisms. In order to define the genetic contribution to insulin‐dependent diabetes mellitus in an Indian population we have analysed 58 unrelated Dravidian (South Indian) insulin‐dependent diabetic patients and 43 controls. In insulin‐dependent diabetes an increased frequency of the Taq 1 DQβ restriction fragment length polymorphisms designated T2omega/T6 (relative risk = 10.6), and of homozygotes for Taq 1 DQα 4.6 kb (relative risk = 11), was found in the patients. The highest relative risk for insulin‐dependent diabetes mellitus was obtained by comparing patients and control subjects who either (a) co‐inherited DQT2omega/T6 with certain DQα restriction fragment length polymorphisms or (b) were DQα 4.6 kb homozygotes, the combination of (a) and (b) accounting for 55.5% of insulin‐dependent diabetes mellitus subjects and none of the controls (relative risk = 101; 95% confidence limits 93–109).