NOD2 and bacterial infectious disease: The identification of the wall dipeptide (MDP), present in the cell wall of mycobacteria, by NOD2, leads to the stimulation of inflammatory responses to deal with bacterial infection, such as the expression of IL-32. In people with leprosy, this cytokine acts in the defense against M. leprae. It indicates that in vivo, the MDP structure of M. leprae does not significantly influence the activation of immunity. M. leprae MDP, in addition to IL-32, it also induced the expression of IL-1β, IL-6, TNF-α and IL-12p40 by monocytes, as well as acting in the differentiation of dendritic cells.