IL6 and Alzheimer disease: HSV-infected cells can contribute to the progression of AD and lowered synaptic density through secretion of IFN-β, IFN-γ, IL-1β, IL-6, chemokine (C–X–C motif) ligand 8 (CXCL8), TNFα, and TGFβ, the immunosuppressive cytokine [71,72,73,74], for which up-regulation is observed both in human AD brain samples, and in transgenic murine models of AD [75,76,77].