Background The association of rheumatoid arthritis (RA) with HLA-DRB1 alleles sharing sequences in the third hypervariable region has been reported in several investigations, but genetic analyses suggest the possible involvement of other HLA class II genes in conferring susceptibility.
Objectives We have investigated the distribution of HLA-DQB1-DRB1 polymorphism in 87 RA patients from southern Croatia and 141 healthy controls. RA patients were predominantly females (83 females vs 5 males).
Methods All patients and controls were tested for HLA class II alleles (DRB1, DQA1, and DQB1) by PCR-SSP method.
Results Distribution of predisposing DRB1 alleles according to the shared epitope (SE) model showed that 11 patients were homozygous for the predisposing alleles. Additional 48 patients carried one of the SE predisposing alleles (*0101, *1001, *0401, *0404, *0405, *0408). Distribution of DQB1 alleles among patients with SE-positive DRB1 alleles revealed that all DRB1*0101 and *1001 patients were DQB1*0501 positive. Among twenty patients with SE-positive DRB1*04 alleles, three different DQB1 alleles were observed (DQB1*0301, *0302 and *0201). Remaining 26 patients with SE-negative DRB1 alleles were additionally analysed for the presence of DQB1*0301, *0302 and *0201 alleles. All eight patients with SE negative DRB1*04 alleles (DRB1*0402, *0403, *0407) were DQB1*0302 positive. Among the remaining non DRB1*04 patients, 16 were either DQB1*0301 or *0201 and only two patients did not carry neither DQB1*0301 nor *0201.
Conclusion These data suggest that in patients with SE negative DRB1 alleles, DQB1*0301, *0302 and *0201 alleles should be considered as a genes contributing to the RA predisposition. DQB1*0301, *0302 and *0201 alleles should be considered as a genes contributing to the RA predisposition.