HCAR2 and colitis: As ligands for G protein-coupled receptors (GPCRs), SCFAs activate GPR41, GPR43, and GPR109A to modulate immunity: GPR43 activation induces NLRP3 inflammasome assembly, epithelial IL-18 secretion, neutrophil recruitment, and Treg differentiation/suppression (364); GPR109A activation increases monocyte anti-inflammatory mediators and induces Tregs to prevent colitis and carcinogenesis (365).