Issues

Control of infection with virulent, but not avirulent, Mycobacterium tuberculosis (Mtb) in mice requires T helper type 1 (Th1)-induced synthesis of inducible nitric oxide synthase (NOS2) by infected macrophages at sites of infection. Shown (right) are macrophages in a lung lesion of a wild-type mouse stained brown for NOS2 by immunocytochemistry, and containing acid fast virulent Mtb bacilli stained red by acid fast staining. At sites of Mtb infection in the lungs NOS2 gene-deleted mice (left) NOS2-positive macrophages are absent, and the lesions are massively populated by infected neutrophils in different stages of degeneration. See related article by Jung et al., pp. 991-998.