Concerning the negative regulation of IBD, lack of Axl and MER signaling upregulates the production of proinflammatory mediators, such as nitric oxide synthase 2 (Nos2), IL-6, IL-17α, TNF, and IL-12p35, and reduces negative regulators, such as IL-10, TGF-β, and resistin-like molecule-α (RELM-α), of inflammation by suppressing alternative M2 macrophage in intestinal lamina propria of DSS-induced colitis18. This evidence concerns the gene NOS2 and inflammatory bowel disease.