CD4 and Alzheimer disease: We then assessed whether the CD4+ T cell levels were associated with their functional cytokines in AD patients, and the correlation analysis showed that circulating Th1, Th2, Th9, Th17, Th22, and Treg levels were positively correlated with plasma IFN-γ, IL-4, IL-9, IL-17, IL-22, and IL-35 concentrations, respectively (Figures 3(c)–3(h)).