Protective & risk DR phenotypes in Asian Indian patients with rheumatoid arthritis.

This study of 168 north Indian patients with rheumatoid arthritis (RA) confirms the significant association of susceptibility to RA with DR4 specificity (P less than 0.0001). This association was observed equally in familial as well as sporadic patients. The HLA-DR2 and DR5 alleles were identified to be conferring protection in RA, DR5 being reduced significantly in the non-familial patients only. None of the other DR antigens revealed any association with RA in this population, including the DR4 negative group of patients. An analysis of the DR phenotypes in patients and controls revealed that DR4 in combination with DR1 provided the highest relative risk (71.9) followed by DR4, DR4 (RR = 4.1). These results demonstrate that susceptibility to RA is not due to a single HLA specificity but the effect of a group of related epitopes occurring in common among subtypes of DR4 as well as in some DR1 alleles.