TNF and Alzheimer disease: Among the neurochemical changes in AD, IFN-γ, TNF-α, IL-1β, IL-2, and IL-8 are elevated along with lower levels of tryptophan and increased kynurenine levels in serum samples from AD patients (Widner et al., 1999; Alsadany et al., 2013; Niranjan, 2013).