Analysis of Killer Cell Immunoglobulin-like Receptor Genes and Their HLA Ligands in Iranian Patients with Ankylosing Spondylitis

Ankylosing Spondylitis (AS) is a chronic rheumatic disease which mainly involves the axial skeleton. It seems that non-HLA genes, as well as HLA-B27 gene, are linked to the etiology of the disease. Recently, it has been documented that KIRs and their HLA ligands are contributed to the Ankylosing Spondylitis. The aim of this study was to evaluate the KIR genes and their HLA ligands in Iranian AS patients and healthy individuals. The present study includes 200 AS patient samples and 200 healthy control samples. KIR genotyping was performed using the polymerase chain reaction sequence-specific primer (PCR-SSP) method to type the presence or absence of the 16 KIR genes, 6 known specific HLA class I ligands and also, two pseudogenes. Two KIR genes (KIR-2DL3 and KIR2DL5), and among the HLA ligands, two HLA ligands (HLA-C2Lys80 and HLA-B27) genes were significantly different between case and control groups. In addition, we found some interesting KIR/HLA compound genotypes, which were associated with AS susceptibility. Our results suggest that the AS patients present more activating and less inhibitory KIR genes with combination of their HLA ligands than healthy controls. Once the balance of signal transduction between activating and inhibitory receptors is disturbed, the ability of NK cells to identify and lyse the targets in immune responses will be compromised. Accordingly, imbalance of activating and inhibitory KIR genes by up-regulating the activation and losing the inhibition of KIRs signaling or combination of both might be one of the important factors which underlying the pathogenesis of AS.