NOD2 and Alzheimer disease: Stimulation with S. aureus-associated NOD2 ligand MDP can induce the release of inflammatory cytokine IL-6 and chemokine CXCL8 via activating mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) and NF-κB pathways in the co-culture of human dermal fibroblasts and human eosinophils, which are the principal effector cells in allergic inflammation commonly found in the skin biopsies of AD patients, but such stimulating effects were not observed in human basophils [16].