SAT0163 Absolute number of peripheral cd4-cd25+foxp3+t cells decreases and restores after low-dose interleukin-2 treatment in rheumatoid arthritis
Authors: X. Jia, H. An, K. Fan, F. Li, C. Gao, X. Li
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background:</h3> Recently, several studies have suggested that abnormal quantity and function of regulatory T cells (Tregs) may play a vital role in the development of rheumatoid arthritis (RA). CD25<sup>+</sup>FOXP3<sup>+</sup> T cells include CD4<sup>+</sup> (CD4<sup>+</sup> Tregs) and CD8<sup>+</sup> cells (CD8<sup>+</sup> Tregs). Recently studies have shown that CD8<sup>+</sup> Tregs also have immunosuppressive function, similar to even stronger than CD4<sup>+</sup> Tregs, and are more sensitive to IL-2 in vivo. However, the status of CD8+Treg cells in RA is unknown. <h3>Objectives:</h3> Our study was designed to clarify the level of CD4<sup>-</sup>CD25<sup>+</sup>FOXP3<sup>+</sup> T cells in RA patients, and to investigate the role of low-dose interleukin-2 (IL-2) therapy in the regulation of CD4<sup>-</sup>CD25<sup>+</sup>FOXP3<sup>+</sup> T cells in RA patients to provide another theoretical basis besides CD4<sup>+</sup> Tregs to IL-2 therapy. <h3>Methods:</h3> Three hundred and four RA patients (diagnosis according to the 2010 ACR criteria) were enrolled; no treatment group (N = 75), DMARDs treatment group (N = 73), low dose IL-2 treatment group (50WIU/day × 5 days, subcutaneous injection) (N = 156), and healthy control group (N = 90). The absolute numbers of CD4<sup>-</sup>CD25<sup>+</sup>FOXP3<sup>+</sup> T cells in peripheral blood were detected by flow cytometry. We assumed that CD4<sup>-</sup> T cells with CD25<sup>+</sup> and FOXP3<sup>+</sup> were mostly CD8<sup>+</sup>CD25<sup>+</sup>FOXP3<sup>+</sup> Treg cells, which was CD4<sup>-</sup>CD25<sup>+</sup>FOXP3<sup>+</sup> T cells in this study. The levels of CD4<sup>-</sup>CD25<sup>+</sup>FOXP3<sup>+</sup> T cells among these groups were compared with that of health group or each other respectively, and then the statistical software SPSS 20.0 was used for analysis; <i>p</i>&lt;0.05 was considered significant. <h3>Results:</h3> As compared with the healthy group, the absolute number of CD4<sup>-</sup>CD25<sup>+</sup>FOXP3<sup>+</sup> T cells decreased significantly in the untreated RA patients [0.94(0.41,1.61) vs 1.31(0.72,2.52), P&lt;0.001] and more dramatically in DMARDs treatment patients [0.86(0.36,1.83) vs 1.31(0.72,2.52), P&lt;0.01]. After treatment with IL-2, the absolute count of CD4<sup>-</sup>CD25<sup>+</sup>FOXP3<sup>+</sup> T cells increased significantly compared with that before treatment [0.91(0.48,1.54) vs 2.10(1.12,3.56), P&lt;0.001]. <h3>Conclusions:</h3> The absolute number of CD4<sup>-</sup>CD25<sup>+</sup>FOXP3<sup>+</sup> T cells in untreated RA patients were lower than those health, implying that CD4<sup>-</sup>CD25<sup>+</sup>FOXP3<sup>+</sup> T cells deficiency was caused by disease itself but not immunosuppressive therapy, which may be an important factor in the pathogenesis of RA. The traditional DMARDs therapy did not improve this reduction. Low dose IL-2 can increase the absolute number of CD4<sup>-</sup>CD25<sup>+</sup>FOXP3<sup>+</sup> T cells in peripheral blood. We are about to detect the number of CD8<sup>+</sup>CD25<sup>+</sup>FOXP3<sup>+</sup> Treg cells accurately to verify this theory. <h3>Disclosure of Interest:</h3> None declared