Shared epitope and polymorphism of MICA and NKG2D encoding genes in Greek and Polish patients with rheumatoid arthritis

The present study aimed to analyse and compare the distribution of MICA (rs1051792) and NKG2D/KLRK1 (rs1154831, rs1049174, rs2255336) polymorphisms in 61 Greek and 100 Polish patients with rheumatoid arthritis in relation to the presence of the HLA-DRB1 shared epitope and clinical parameters. Genotyping of selected polymorphism was performed using real-time PCR. HLA-DRB1 shared epitope alleles segregated differently in Greek and Polish patients but in both populations were detected in over 60% of cases. The rs1051792-A variant was more common among SE-positive Polish patients (p = 0.003) while the rs1049174-G allele was more frequently observed in Greeks than in Poles (p < 0.001). Moreover, among Greek patients, the rs1051792-GG homozygotes more frequently presented with anti-CCP antibodies and rheumatoid factor (RF), while carriers of the rs1049174-G variant and rs1154831-CC homozygotes were characterized by lower disease activity scores (p < 0.05 in all cases). These results imply that, in addition to the HLA-DRB1 SE alleles, MICA and NKG2D polymorphisms may also play a role in rheumatoid arthritis.