HCAR2 and Autoimmunity: It has been shown to exert beneficial functions in the maintenance of systemic regulation of host immune response by increasing anti-inflammatory factors, downregulating autoimmunity-related factors, and developing regulatory T (Treg) cells via G-protein-coupled receptors (GPCRs) (e.g., GPR41, GPR43, and GPR109A) (58, –, 61).