HLA class 2 genes in Singaporean Chinese rheumatoid arthritis.

This study analysed HLA class 1 and 2 allele associations in Singaporean Chinese patients with RA. Seventy patients (ARA definite or classical) and 80 controls were typed for HLA class 1 alleles by serology and class 2 alleles by serology and the PCR/SSO method. RA patients had higher frequencies of DRB10405 (40 vs 12.5%; corrected probability value (PC) < 0.02, relative risk (RR) = 4.7, 95% confidence limit (CL) 2.1-10.6), DRB11001 (14.3 vs 1.3%; PC = 0.06, RR = 13.2, 95% CL 1.6-105.7), DQB10401 (38.6 vs 12.5%; P = 0.006, RR = 4.4, 95% CL 1.9-10.0) and DQB10501 (20 vs 5%; PC = 0.048, RR = 4.8, 95% CL 1.5-15.2). It is concluded that Chinese RA is associated primarily with HLA DRB10405 and DRB11001 which share common amino acid sequences in the third hypervariable region of the DR beta chains shown to be associated with RA in other ethnic groups. Patients without DRB1*0405 and 1001 had a higher frequency of DRB10901, which is in linkage disequilibrium with HLA B46 in the Chinese.