In one meta-analysis, which included 54 studies measuring cytokine concentrations (40 in peripheral blood and 14 in the CSF), patients with AD exhibited higher concentrations of IL-6, TNF-α, IL-1β, TGF-β, IL-12, and IL-18 in peripheral blood, and elevated levels of TGF-β in CSF, compared to healthy controls [141]. Here, IL18 is linked to Alzheimer disease.