IL4 and Alzheimer disease: Experiments on full-thickness human skin equivalents to determine whether skin inflammation affects epidermal lipid biosynthesis showed that treatment with a cocktail of IL-4, IL-13, and IL-31 resulted in significantly lower mRNA levels of genes encoding ELOVL1, acid SMase and β-GCase, which are involved in lipid chain elongation and ceramide synthesis, suggesting a direct role of TH2 cytokines on lipid biosynthesis and alterations in AD [33].