TNF and proliferative diabetic retinopathy: In patients with proliferative diabetic retinopathy increased vitreous concentrations of the interleukin-1beta (IL-1beta), IL-6, soluble IL-2 receptor (sIL-2R) and IL-8 were found [12], whilst the serum of same patients contained elevated levels of tumor necrosis factor-alpha (TNF-alpha), IL-6, IL-8 and sIL-2R [12,13,22].