5. Perspectives
Currently, massive evidences have shown that NOD2 is not only an intracellular PRR for MDP, but more importantly, a buffer for maintaining immune homeostasis. By binding to various molecules or undergoing different post-translational modifications, NOD2 can trigger diverse immune responses, including the secretion of pro-inflammatory cytokines, lymphocyte activation, autophagy regulation, synergistic interactions with other pattern recognition receptors, immune training, immune tolerance, etc. These diverse functions also determine that NOD2 may play different roles in acute infections, chronic infections, or autoimmune diseases. Therefore, regulating NOD2 activity is a promising strategy for the treatment of these diseases, which requires more in-depth research on the roles of NOD2 in different immune environments.