Functional macrophages and gastrointestinal disorders

Figure 2 Current views about intestinal macrophages. (1) LP-resident CD169⁺ MΦ reside at the bottom-end of the LP microenvironment, far away from the epithelium-LP border. CD169⁺ MΦ recruit inflammatory monocytes by producing CCL8. CD109⁺ MΦ can be considered as a "conservation corps" in the intestine because they likely respond to the collapse of frontline defense; (2) M₂ MΦ are MHCII⁺, producing IL-10 and expressing CD163, CD206 and lectin receptors. They do not produce proinflammatory mediators with signals of stimulation. In addition, they produce tissue-repairing factors, such as VEGF, actin and metalloproteinases; and (3) GPBAR1 is essential to maintain intestinal immune homeostasis by regulating M₁/M₂ MΦ. BAR501 is a small-molecule stimulus for GPBAR1. It contributes to this regulative process, depending on the production control of IL-10. Exposure to BAR501 leads to increased expression of IL-10, TGF-β mRNA and the percentage of CD4⁺/Foxp3⁺ cells. IL: Interleukin; LP: Lamina propria; MΦ: Macrophages; TGF: Tumor growth factor; VEGF: Vascular endothelial growth factor.