Effect of different cytokines in combination with IL-15 on the expression of activating receptors in NK cells of patients with Behçet's disease.

Behçet's disease (BD) is a systemic, autoinflammatory, chronic disorder which affects various parts of the body in genetically susceptible individuals. BD has a multi-factorial etiopathogenesis which encompasses both innate and adaptive arms of immunity. NK cells, which kill virus-infected or malign cells and provide interaction between adaptive and innate immune system, are also known to involve in the pathogenesis of autoimmune/autoinflammatory diseases including BD. NK cells function in immune responses via the signals obtained from surface-expressed activating and inhibitory receptors. In this study, we aimed to explore NK cell activation status by measuring the levels of activation marker CD69 and activating receptors NKG2D, NKp30, and NKp46 as well as proliferative and cytotoxic capacities in response to stimulation with interleukin (IL)-15-combined cytokines in BD patients. CD4⁺ and CD8⁺ T cell responses were also evaluated to compare with those of NK cells. As a result, the expression of activating receptors on NK cells was demonstrated to be varied among patients with active and inactive BD and healthy controls. The proliferation levels of NK cells were elevated in BD patients, especially in inactive phase of disease compared to healthy controls. Additionally, CD107a levels of inactive BD patients were detected to be lower in comparison with healthy controls and active BD patients. These findings suggest that BD patients in active and inactive phases display different activation status of NK cells which indicate NK cells might be associated with immune attacks and remissions during the course of BD.