CD4 and retinal disorder: In the PB of T2DM patients with retinopathy or proliferative retinopathy, intracellular miR-155, and serum transforming growth factor-β (TGF-β) levels are significantly upregulated while the percentage of CD4 + CD25 + forkhead box (Fox) P3 + T-regs was lower compared to non-diabetic retinopathy and healthy control group (Fig. 4a).