Objective: To investigate the frequency and distribution of DRB1 and DQB1 alleles in Patients with rheumatoid arthritis (RA) and analyze the relationship between clinical response to methotrexate (MTX) and the HLA-DR and HLA-DQ genotypes in these patients.
Methods: In this case-control study, the HLA-DRB1 and HLA-DQB1 polymorphism in 91 RA patients and 91 healthy controls was done using polymerase chain reaction and sequence specific primers.
Results: There was no statistical difference in frequencies of HLA-DRB1*03, DRB1*04, DRB1*07, DRB1*10, DRB1*11, DRB1*12, DRB1*13, DRB1*14, DRB1*15 and DRB1*16 genotypes between patients and controls. However, DRB1*01 was found to be significantly more common (p=0.015) in RA patients compared to controls. HLA-DRB1*15 was more common in patients (43.5%) compared to controls (30.8%) but results were not significant. HLA-DRB1*08 and DRB1*09 were present in negligible number in patients as well as controls while HLA-DRB1*12 was conspicuously absent in controls. Similarly, DQB1*06 was also significantly more common (p = 0.01) among the patients compared to healthy control subjects, while there was no statistical difference in the frequencies of DQB1*02, DQB1*03, DQB1*04 and DQB1*05 among the cases and the controls. RA susceptibility in most patients appeared to be associated with the HLA-DRB1*01/DQB1 *06 genotype. Regarding association between HLA-DR or HLA-DQ genotype and clinical response to methotrexate (MTX), the data showed that with the exception of HLA-DRB1*03, there appears to be no association between the particular subtypes of HLA-DR and HLA-DQ. HLA-DRB1*03 was significantly-more common among non-responders to MTX alluding to the possibility that another genes responsible for MTX metabolism, might be in linkage disequilibrium with HLA-DRB1*03 in the Pakistani population, thereby making such individuals non-responsive to MTX-therapy.
Conclusion: RA susceptibility in most Pakistani patients is associated with the HLA-DRB1*01/DQB1*06 genotype. HLA-DRB1*03 was found to be significantly more common among non-responders to MTX treatment suggesting that Pakistani patients with this genotype are less likely to benefit from MTX.