Abnormal Expression Pattern of the IL-2 Receptor β-Chain on CD4(+) T Cells in ANCA-Associated Vasculitis

Background/Aim. ANCA-associated vasculitis (AAV) is a small-vessel vasculitis of autoimmune origin. In addition to autoantibodies, T cells have a pivotal pathophysiological role in this disease. T-cell homeostasis and immune tolerance critically depend on IL-2 and its receptor expressed by T cells. In this study, we investigated the IL-2 receptor (IL-2r) expression on CD4(+) T cells in AAV. Methods. Thirty patients with AAV and 15 age-matched healthy controls (HC) were enrolled. T cells from peripheral blood were analysed by flow cytometry for expression of the IL-2r α- and β-chain. Results. The IL-2r α-chain was overexpressed in AAV as compared to HC (36 ± 16% versus 20 ± 9%, P < 0.005). The IL-2r-β-chain expression was significantly reduced on CD25(+) CD4(+) T-cells and CD4(+)CD25(+)FoxP3(pos) regulatory T-cells (Tregs; AAV versus HC: 48 ± 14% versus 62 ± 9%, P = 0.002 and 38 ± 18% versus 68 ± 5%, P = 0.002). Low β-chain expression in AAV was associated with relapsing disease and systemic vasculitis with renal involvement. Conclusion. The IL-2r expression pattern is abnormal in AAV. To our knowledge, we are the first to show that the β-chain expression is drastically diminished on T cells in AAV and related to a less favorable disease course. Given the indispensable function of the β-chain in IL-2 signaling of T cells, diminished expression may contribute to disturbed immune homeostasis in AAV.