CD4 and type 2 diabetes mellitus: Compared with the controls, T2DM patients had significantly increased levels of serum IL-6 (SMD, 1.28; 95% CI, 0.73 to 1.83; p < 0.001) (Figure 2), TGF-β (SMD, 2.88; 95% CI, 2.37 to 3.40; p < 0.001) (Figure 3), and TNF-α (SMD, 1.56; 95% CI, 1.10 to 2.02; p < 0.001) (Figure 4) but significantly decreased the percentage of CD4+CD25+Foxp3+Treg (SMD, −0.47; 95% CI, −0.72 to −0.23; p < 0.001) (Figure 5) and the level of serum IL-10 (SMD, −1.37; 95% CI, −2.32 to −0.42; p = 0.005) (Figure 6).