Expression and secretion of IL-4 is induced by neuroinflammatory insults in activated immune cells and damaged neurons and IL-4-activated microglia produce a series of mediators, including neurotrophic factors, matrix remodeling, and proteolytic enzymes that help reduce neuroinflammation and promote tissue repair, as shown in experimental models of neurodegenerative diseases [18, 21, 30–32]. This evidence concerns the gene IL4 and neurodegenerative disease.