CCL17 and Alzheimer disease: Chemokines (thymus and activation-regulated chemokine; TARC/CCL17 and macrophage-derived chemokine; MDC/CCL22) and cytokines (IL-25, IL-33, and TSLP) are also essential inflammatory mediators in the development of AD, and their expression has been reported to increase in patients with AD [9,10,11].