Associations of HLA-DRB1 alleles with anti-citrullinated protein antibody-positive and anti-citrullinated protein antibody-negative rheumatoid arthritis in northern east part of Turkey

Abstract

The aim of this study was to investigate the associations between human leukocyte antigen (HLA)-DRB1 alleles with genetic susceptibility to rheumatoid arthritis (RA) and production of antibodies against cyclic citrullinated peptide (anti-CCP antibody) and rheumatoid factor (RF) in Turkish RA patients. We studied 291 RA patients and 253 controls. Genotyping was performed by polymerase chain reaction with sequence-specific oligonucleotide probes hybridization method. Serum levels of anti-CCP antibody, IgM-RF and high sensitive C-reactive protein titers were measured by commercial kits using immunological methods. We found that HLA-DRB1*04 and *09 alleles were associated in anti-CCP+ and anti-CCP+ RA patients (P < 0.0001 and P < 0.001, respectively), while DRB1*01 and *04 were determined to be higher in RF+ RA patients (P < 0.001 and P < 0.0001, respectively). Moreover, DRB1*11 and DRB1*13 alleles were determined to be lower in RF and anti-CCP/RF+ RA patients (P < 0.001 for both). HLA-DRB1*04 was identified as a common responsible allele for susceptibility to the disease in anti-CCP, RF and anti-CCP/RF- RA patients (P = 0.0018, P = 0.0004 and P = 0.0023, respectively). HLA-DRB1*13 allele alone was found to be protective against to anti-CCP+ and RF- RA (P = 0.0003 and P = 0.006, respectively). On the contrary, there was no protective allele in anti-CCP/RF- RA as well as anti-CCP- RA patients. This study indicates that associate and protective HLA-DRB1 allele distributions are different in autoantibody (anti-CCP or RF or anti-CCP/RF)+ RA and autoantibody- RA patients, with exceptions of DRB1*04 and DRB1*13.