CCL17 and Alzheimer disease: Keratinocytes in skin lesions from AD patients can produce thymus and activation-regulated chemokine (TARC)/CCL17 and macrophage-derived chemokine (MDC)/CCL22, which are chemoattractive for T-helper (Th) 2 cells [4], and when these cells infiltrate skin lesions, they release various inflammatory cytokines, such as interleukin (IL)-4, IL-5, IL-10, and IL-13.