To analyze the molecular basis for HLA-DR associations with rheumatoid arthritis(RA) in the han nationality of Chinese population.
Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) techniques were used to dertermine DRB1 alleles in 35 unrelated patients with RA and 100 healthy controls from the Han nationality.
The frequency of DR4(DRB1 * 04) was 51.4% in RA patients and 24.0% in the healthy controls(P < 0.01, RR = 3.3). There was a significant increase in the presence of the amino acid sequences QKRAA or QRRAA both in the RA patients overall compared with the healthy group(65.7% vs 30.0%, P < 0.001) and in DR4+ RA patients compared with DR4+ healthy individuals(100% vs 75.0%, P < 0.05). Substitution of residues in QKRAA, V85 and G86 appeared to correlate with relative risk for RA, among the subjects having 0-1 amino acid substitution, RA occurred in 48.8%, whereas in subjects with 2-3 amino acid changes, RA was present in only 16.7%.
These results suggest that DR4 is strongly associated with RA in the Han nationality, and the dominant effect that determines susceptibility to RA is associated with QKRAA or QRRAA as well as V85 and G86.