LINKAGE BETWEEN RHEUMATOID-ARTHRITIS SUSCEPTIBILITY AND THE PRESENCE OF HLA-DR4 AND DR-BETA ALLELIC 3RD HYPERVARIABLE REGION SEQUENCES IN SOUTHERN CHINESE PERSONS

Objective. To analyze HLA-DR and DQ associations with rheumatoid arthritis (RA) in patients from southern China. Methods. In 66 patients and 45 controls, restriction fragment length polymorphism studies were performed using DRB, DQA, and DQB probes, and DRB allele-specific typing of polymerase chain reaction-amplified DRB DNA. Results. The frequency of HLA-DR4 was significantly increased among RA patients (42.4% versus 17.8%). Increased frequencies of the DQA3 allele (77.8% versus 48.9%) and the DQBI*0302 allele (71.0% versus 46.3%), which are in linkage disequilibrium with DR4, were also found. Oligonucleotide typing showed that the amino acid sequence LLEQRRAA, spanning amino acid positions 67-74 of the DR-beta-molecule, was found in 19 of 49 patients and 5 of 32 controls. The main DR4 allelic subtypes found in the population were DRBI*0404 and DRB1*0405, both of which carried the sequence. There was no difference in subtype distribution between patients and controls. Conclusion. Chinese RA patients have an increased frequency of HLA-DR4 alleles which possess the same DRB third allelic hypervariable sequence shown to be associated with susceptibility in Caucasian RA patients.