Do KIR genes impact the susceptibility to ankylosing spondylitis in Polish patients?

Abstract

Aim: Ankylosing spondylitis (AS), a chronic inflammatory arthritis, is strongly associated with HLA-B27 gene worldwide. Among immunocyte receptors reacting with HLA-B27 are killer cell immunoglobulin-like receptors (KIRs ), particularly KIR3DL1 and KIR3DL2. The KIR family includes both activating and inhibitory receptors. These may be expressed on NK cells and subtypes of T cells, which via activating/inhibitory signals regulate the activity of immunocompetent cells and potentially have an impact on inflammation and autoimmunity occurrence. However, reports on the role of KIRs in AS are controversial. Material/Methods: We examined the possible associations of KIR genes in 192 patients diagnosed with AS compared with 191 control individuals. KIR genes were typed using PCR-SSP method. Results: No single KIR gene frequency was found to differ between patients and controls. Nevertheless, the genotypes containing three genes encoding activating KIRs, as well as those characterized by ratios of activating to inhibitory KIRs close to 1:2 (0.5–0.6) were significantly less frequent in AS than in controls. On the contrary, higher ratios (0.67–1.67) were more frequent in AS in comparison to controls. Conclusions: Our results suggest a protective effect of the presence of 3 (but not more) genes encoding activating KIRs, and of a ratio of activating to inhibitory KIRs close to 1:2 (0.5–0.6) but not higher. On the other hand, higher activating to inhibitory KIR ratios seem to predispose to AS. This suggests a very narrow window for optimal ratio of activating to inhibitory KIRs.