Figure 3.

Cytokine secretion does not differ between matrix metalloproteinase 1 (MMP-1)–expressing mice and wild-type (WT) mice, but collagen is absent in regions of caseous necrosis. A–F, Concentrations of tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β), interleukin 12 (IL-12), interferon γ (IFN-γ), monocyte chemotactic protein 1 (MCP-1), and IFN-γ–inducible protein 10 (IP-10) were measured in mouse lung homogenates at 22 weeks after infection by Luminex array. Mycobacterium tuberculosis infection upregulated each of these proinflammatory mediators in all infected mice, but there were no significant differences related to the genotype of the mice. Open bars denote uninfected mice, and filled bars denote M. tuberculosis–infected mice. Mean values ± standard errors of the mean are shown. G–I, Total collagen was analyzed by Picrosirius red staining. In wild-type mice (G) and matrix metalloproteinase 9 (MMP-9)–expressing mice (I), alveolar wall collagen remained intact in regions of macrophage infiltration. However, in MMP-1–expressing mice, collagen was destroyed and colocalized with regions of caseous necrosis (H). Data are representative of 5 mice per group infected in 3 independent experiments. Scale bars, 50 µm. Abbreviation: NS, not significant.