Expression of T-helper-associated cytokines in patients with type 2 diabetes mellitus with retinopathy

Purpose: Recent studies showed that immunological mechanisms were involved in the pathogenesis of diabetic retinopathy (DR). T-helper (Th) cells play an important role in chronic inflammatory disorders and autoimmune diseases. Whether Th cells participate in the pathogenesis of DR remains unclear. Methods: To evaluate the role of Th cells in the pathogenesis of type 2 diabetes mellitus with retinopathy, the concentrations of interferon (IFN)-γ, interleukin (IL)-1β, IL-2, IL-4, IL-5, IL-6, IL-9, IL-10, IL-12 p70, IL-13, IL-17A, IL-22, and tumor necrosis factor (TNF)-α in the serum of 29 patients with type 2 diabetes mellitus and 30 normal controls were measured with FlowCytomix Technology. IL-22 levels in unstimulated and stimulated peripheral blood mononuclear cells (PBMCs) were examined with enzyme-linked immunosorbent assay. Results: We found that the mean IL-22 serum levels were slightly lower in diabetic patients than in normal controls. The IL-22 level of PBMCs was significantly elevated in patients with proliferative diabetic retinopathy compared with the level in patients with non-proliferative diabetic retinopathy, patients with non-DR, and healthy controls. Additionally, the IL-22 serum and PBMC levels were positively correlated with the duration of diabetes. Serum levels of other associated cytokines showed no significant change in diabetic patients compared to controls. Conclusions: These results indicate a possible role of Th22 cells in DR, and IL-22 may be involved more in the pathogenesis of proliferative diabetic retinopathy than in other stages of DR.