NOS2 and infection: The surface expression of these lipids on mycobacteria masks ligands for toll-like receptors (TLRs) that are required for the induction of inducible nitric oxide synthase (iNOS)-positive M1-type microbicidal macrophages, and instead recruits iNOS-negative non-microbicidal macrophages (referred to as “permissive macrophages”) to the site of infection, thereby facilitating the intracellular Mtb survival and propagation20.