CCL17 and Alzheimer disease: Keratinocytes are the source of cytokines including inflammatory cytokines (IL-6, IL-1α, IL-1β, IL-18, and TNF-α), immunoregulatory cytokines (IL-7, IL-12, IL-15, IL-16, and GM-CSF), and chemokines (IL-8, TARC, RANTES, and MCP-1) in AD skin.