A serine protease inhibitor induces necrosis of infected macrophages within granulomas during activation of tuberculosis. Mus musculus

Granulomas function in humans during tuberculosis by focusing production of host antimicrobial factors against the causative bacterial agent Mycobacterium tuberculosis to contain infection. We show that mice unable to produce nitric oxide –itself an important antimicrobial molecule- demonstrate functional granulomas in the lung able to control infection after dermal infection. Disease in the lung was activated by administration of neutralising antibody against either TNF-α, which disrupted granuloma integrity, or INF-γ, which resulted in development of caseous necrosis within granulomas reminiscent of active human tuberculosis. In the latter case, the serpin protease inhibitor serpinb3a and its target protease, cathepsin G are highly expressed in cells local to necrotic regions in granulomas and serpinb3a induces necrosis of infected macrophages independently of cathepsin G binding. Therefore a single host protein is capable of inducing necrosis and bacterial growth during intracellular infection. Overall design: Microarray experiments were performed as dual-color hybridizations on Agilent mouse whole genome catalog 44K arrays. To compensate for dye-specific effects, a dye-reversal color-swap was applied.