DQCAR 113 and DQCAR 115 in combination with HLA-DRB1 alleles are significant markers of susceptibility to rheumatoid arthritis in the Korean population

We have investigated HLA region microsatellite polymorphisms in rheumatoid arthritis (RA) which are known to be associated with HLA class II alleles i n the Korean population. Ninety patients with RA and 106 controls were empl oyed for this study, in which TAP1CA, DQCAR, D6S273, HLA-DRB1, -DQA1 and -D QB1 allele typing were performed. DQCAR 113 (RR=3.2, P<0.0002), DQCAR 115 ( RR=3.6, P<0.0001) and heterozygous DQCAR 113/115 (RR=11.2 P<0.0001) frequen cies were significantly increased in the RA group compared with the control group. The HLB-DRB1 genotypes of patients who had DQCAR 113/115 alleles we re defined as DRB1*04 and/or DRB*09. There was no significant difference:be tween RE and controls in D6S273 and TAP1CA allele frequencies. We demonstra ted that HLA-DRB1*0405 (RR=6.6, P<10(-6)), DQA1*03 (RR=5.2, P<10(-6)), Univ ersity of Korea. Se DQB1*04 (RR=3.5, P<0.002) alleles were useful markers o f susceptibility to RA. in Koreans. The frequency of HLA-DRB1*0405 was high er in DQCAR 113 allele-positive RA (68.1%) than in DQCAR 113 allele-negativ e (16.3%) and total RA (43.3%) groups, and the susceptibility risk of DQCAR 113 allele to RA was more increased in the DRB1*0405-positive group (RR=5. 5, P<0.04). On the other hand, DQCAR 115 allele was more significantly asso ciated with susceptibility to RA in HLA-DRB1*0405-negative patients (RR= 5. 1, P<0.0005), and the association between RA and HLA-DRB1*0405 was also sig nificantly associated with DQCAR 115 allele-negative patients (RR=13.2, P<0 .00001) as compared with DQCAR 115 allele-negative control groups. HLA-DRB1 *0405-DQA1*03-DQCAR113-DQB1*03 haplotype showed high relative risk value (R R=17.7, P<0.0002). In conclusion, the DQCAR allele in combination with HLA class II especially DR, is probably a useful risk marker for RA susceptibil ity in the Korean population.