HLA-DQw alloantigens and pulmonary dysfunction in rheumatoid arthritis.

HLA-DR4 and keratoconjunctivitis sicca (secondary Sjögren's syndrome) are associated with abnormal pulmonary function in patients with rheumatoid arthritis. Since recent investigations have found that much of the genomic polymorphism of the HLA-DR4 haplotype comes from the closely linked DQw allele, we reanalyzed this set of data to evaluate the relationship between the DQw allotypes and pulmonary function in rheumatoid arthritis. Using a step-wise regression analysis, we found that the presence of DQw1 was a stronger predictor of an abnormal forced vital capacity (FVC), forced expiratory volume in one second (FEV1), and carbon monoxide diffusing capacity (D) than the presence of DR4, keratoconjunctivitis sicca, smoking status, or any other clinical parameter. DQw1-positive patients had a mean (+/- SD) percent of predicted FEV1, FVC, and D of 84.2 (+/- 19.8), 88.0 (+/- 17.9) and 85.6 (+/- 20.9) percent, respectively, all significantly lower than DQw-1 negative patients (p = 0.02, 0.02, and 0.03). Smokers with the heterozygous phenotype, DQw1/DQw3, tended to have obstructive disease of the airways, with a mean (+/- SD) FEV1 of 80.1 +/- 24.4 percent of predicted, compared to 95.7 +/- 12.1 percent of predicted in DQw1/DQw3-negative individuals (p = 0.03). Patients who had a DQw2 allele were more likely to have normal pulmonary function. We conclude that the HLA-DQw1 allotype is a strong predictor of abnormal pulmonary function and that it may identify smoking subjects with rheumatoid arthritis subjects who are prone to develop obstruction of airflow.