IL18 and Alzheimer disease: Studies performed so far describe elevated levels of pro-inflammatory cytokines such as interleukin IL-6, IL-1β, Il-12, IL-18, transforming growth factor (TGF)-β, tumor necrosis factor (TNF)-α [107] or IL-2, CXCL10, C reactive protein, and interferon-γ [108] in the blood of AD patients, while other studies show no significant differences between AD and non-AD subjects in the peripheral levels of IL-1β, TNF-α, IL-6, or C reactive protein [109].