Context: Disease Modifying Anti-Rheumatic Drugs (DMARDs) are aimed to interfere with rheumatoid arthritis (RA) progression and reduce the joint damage; however, not all patients respond alike. Killer-cell immunoglobulin-like receptors (KIR) and their ligands, human leucocyte antigen class I (HLA-I), have been associated with RA pathology; therefore, KIR and HLA genes may influence the treatment response. Materials and methods: We evaluated the association of KIR genotype and their ligands HLA-C genes with the response to DMARDs in RA patients. We included 69 patients diagnosed with RA and 82 healthy individuals as the reference group. KIR and HLA-C genotyping was performed using SSP-PCR. RA patients were assessed at baseline and under treatment at 6 and 12 months; subsequently classified as responders and non-responders in each time period. We evaluated the association between DMARD response and genes using statistical analysis by using Fisher exact test with Bonferroni correction; results were regarded as statistically significant at p < 0.05. Results: Significant difference was observed in gene frequencies of patients and the reference group, KIR2DL2 was associated with RA (p = 0.031, OR = 2.119). We also observed an association between KIR2DS2 and the response to methotrexate (MTX), moreover, the combination KIR2DL2+/KIR2DS2+ was more frequent in responders to MTX (p = 0.043). Discussion and conclusions: In our results, responders and non-responders to DMARDs showed KIR2DS2 and KIR2DL2 different gene frequencies, therefore, these genes could be used as response predictors to DMARDs treatment. Thus, these genes were also associated with disease severity, as well as the treatment response possibly by the immunoregulatory function of NK cells.

Background: Psoriatic Arthritis (PsA) is a seronegative spondyloarthropathy frequently associated with psoriasis. Studies have shown different members of the KIR (Killer Immunoglobulin-like Receptor) gene family may act as potential susceptibility factors; however, data have been inconsistent or with a reduced sample size. Therefore, the objective of this investigation was to determine associations between KIR genes and PsA susceptibility a meta-analysis approach. Methods: We performed a systemic search on PubMed, Scopus, and Web of Science to identify association studies linking KIR genes with PsA susceptibility. The search cut-off was May 2019. Odds Ratio (OR), 95% Confidence Intervals (95% CI), and forest plots were obtained for each KIR gene. Publication bias was evaluated by Begg and Egger linear regression tests. Results: Five articles were included in this meta-analysis. The KIR2DL2, 2DS1, 2DS2, and 2DS3 genes were positively associated with susceptibility to PsA (OR = 1.269, p = .003; OR = 1.392, p < .001; OR = 1.279, p = .002; and OR = 1.230, p = .038, respectively). In Caucasians, positive association with susceptibility to PsA were maintained by KIR2DL2, 2DS1, and 2DS2 genes (OR = 1.257, p = .005; OR = 1.535, p = .003; and OR = 1.267, p = .004, respectively). Conclusion: These associations suggest that KIR2DL2, 2DS1, 2DS2, and 2DS3 genes are susceptibility factors for PsA.