Fig. 3. Functions of NOD2 during mycobacterial infection.Macrophages/monocytes phagocytose mycobacteria, which are digested into MDP following fusion of phagosomes and lysosomes. Nod2 recognizes MDP and produces effectors (TNF, IL-1β, IL-6, IL-12, IL-32, type I IFNs, NO) via the RIP2-NF-κB/MAPK/IRF5 pathway. MDP-dependent IL-32 induces the rapid differentiation of monocytes into DCs. NOD2-dependent autophagy reduces the survival of hidden mycobacteria in MSCs. The NOD2 and TLR4 signaling pathways enhance T-cell initiation in DCs. BCG vaccines enhance bactericidal efficacy through NOD2-trained immunity.