HLA class II polymorphism in patients with type 1 diabetes mellitus from a Brazilian racially admixtured population.

BACKGROUND Several studies have demonstrated a fundamental role for the histocompatibility antigens (ie, human leukocyte antigens or HLA) in the susceptibility of, or protection to, type 1 diabetes mellitus (T1DM). However, this has not been adequately studied in racially admixtured populations. OBJECTIVES To assess the frequency of HLA class II (DQA1, DQB1 and DRB1) associated to susceptibility or protection toT1DM in a Brazilian racially admixtured with diabetes. METHODS Cross-sectional study. The HLA genotyping was performed by a polymerase chain reaction hybridization assay. The racial groups were categorized by self-report and phenotype. The results are expressed as means and standard deviations of the mean, proportions and frequencies. The chi2 and Fisher exact tests were used for the inferential statistics. RESULTS The study population comprised 55 children and adolescents with T1DM. The phenotypic racial group classification demonstrated that, 60% were Mulattoes, 25.5% Whites, 12.7% Blacks and 1.8% from Indian ancestry. The T1DM's susceptibility was associated with an increased frequency of the HLA of risk (-DRB1*0401, -DRB1*0402, DQA1*03, -DQA1*05, -DQB1*02 e -DQB1*0302); and a small frequency of protective alleles (-DRB1*0404, -DRB1*0407, -DQA1*0201, -DQB1*0602, -DQB*0603 e -DQB1*0604) in all subjects. We found a greater frequency of the HLA-DRB1*0302 among Whites when compared to Blacks. CONCLUSIONS This study demonstrates that the frequency and distribution of the susceptibility and protective HLA alleles were similar to studies performed in the Brazilian Southeast and in North Americans and European Caucasians, suggesting that the genetic basis of T1DM has a common origin being little modified by racial characteristics.