IL2 and rheumatoid arthritis: In addition, the serum IL-2 levels of RA patients were positively correlated with Th17/Treg ratios in peripheral blood (r = 0.239, p = 0.013) (Table 5 and Figure 3(g)), while there was no significant correlation between Th17 and Treg cells in peripheral blood (p > 0.05; Table 5 and Figure 5).