CCL17 and Alzheimer disease: D-tryptophan is a metabolite of Bifidobacteria, Lactobacillus and Lactococcus, strongly induces the production of anti-inflammatory factor IL-10 and reduces the secretion of IFN‐γ,IL‐12, and IL‐5 in LPS‐induced KM‐H2 (a human Hodgkin’s disease cell line) cultures, and suppress the expression of the crucial chemokine CCL17 responsible for recruitment of Th2 cells in AD skin lesions (77, 141).