The contribution of HLA-DQB1 coding and QBP promoter alleles to anti-Ro alone autoantibody response in systemic lupus erythematosus.

OBJECTIVE To analyse the influence of HLA-DR, DQ and corresponding DQA1 and DQB1 promoter alleles (QAP and QBP) on the anti-Ro alone autoantibody response in systemic lupus erythematosus (SLE). METHODS Sixty-five unrelated anti-La antibody-negative SLE patients, 37 of them with and 28 without anti-Ro antibodies, were included. Anti-Ro antibodies were determined by both counter-immunoelectrophoresis and enzyme-linked immunosorbent assay. Seventy-four healthy individuals were selected as controls. The patients and controls were analysed for HLA-DRB1, QAP, DQA1, QBP and DQB1 alleles by DNA typing. The allelic frequencies of anti-Ro alone-positive and anti-Ro-negative SLE patients and healthy controls were compared using the chi(2) test or Fisher's exact test as appropriate. RESULTS The DQB1*0202 allele showed a significant positive correlation with anti-Ro alone antibodies [odds ratio (OR)=16.949, P=0.0015, corrected P=0.018], while the QBP5.11 allele and the combination of DQB1*0301 and its promoter QBP3.1 were under-represented in anti-Ro-alone-positive SLE patients (P=0.01, corrected P=0.048 and corrected P=0.048 respectively). CONCLUSIONS The above-mentioned alleles may contribute to the presence or absence of anti-Ro alone autoantibodies in SLE patients.