TNF and type 1 diabetes mellitus: Furthermore, IFN-γ is expressed locally in the CNS65 and activated microglia in the diabetic brain exhibit enhanced IFN-γ expression.66 Activated microglia produce TNF in experimental DR.67 Evidence in support of systemic production of relevant cytokines comes from the observation that there are high serum levels of IFN-γ and TNF in T1D subjects with DR.47, –49