Genetic markers of immunoglobulins and diabetes mellitus in the multiracial population of New Caledonia

GM and KM immunoglobulin allotypes, which are the markers, respectively, of the constant parts of the heavy and the light chains of the IgG1, IgG2 and IgG3 subclasses, have been analysed in diabetic mellitus patients and cont rols living in New Caledonia. We tested 40 Europeans, 256 Melanesians and 4 4 Polynesians, as well as their 340 matched controls, in order to search fo r a genetic susceptibility at those polymorphic loci. All the subjects were tested for G1M (1, 2, 3, 17), G2M (23), G3M (5, 6, 10, 11, 13, 14, 15, 16, 21, 24, 28) and KM (1) by the classical hemagglutination method. The frequ encies of GM haplotypes and KM alleles have been estimated by a maximum lik elihood method. The results are in favour of no influence of the GM and KM loci. The prevalence of diabetes mellitus varies in the populations of New Caledonia: Polynesians are at much higher risk than Melanesians or European s. The GM haplotype distribution differs among ethnic groups; so they provi de a useful marker to measure genetic admixture. The higher prevalence of d iabetes observed among New Caledonians of European origin compared to the p revalence in Europe may be explained by genetic admixture with neighbouring Pacific populations, notably Polynesians (Asian haplotypes are present at a frequency of 9.4%). So, the genetic admixture should be measured in any g enetic epidemiological study. (C) 2000 Elsevier Science Ireland Ltd. All ri ghts reserved.