Figure 2.

Enhanced survival correlates with granuloma formation. (A) Lung sections of mice infected with M. tb-3E5 stained with hematoxylin/eosin reveal typical pathology associated with experimental tuberculosis infection in mice. Multiple granulomas are seen, as well as infiltrating inflammatory cells. (B) Mice infected with M. tb-3E5 reveal a random distribution of AFB (pink bacilli) in lung tissue sections. (C) Immunohistochemistry conducted on subsequent sections reveals moderate production of iNOS in M. tb-3E5-infected mice, paralleling the presence of AFB. (D) Lung sections of mice infected with M. tb-9d8 stained with hematoxylin/eosin reveal similar gross pathology, compared with controls. (E) M. tb-9d8-infected mice reveal a concentration of bacilli within well formed granulomas. (F) Serial sections reveal that iNOS is produced similarly in cells paralleling AFB deposition. In M. tb-9d8-infected mice, however, iNOS production may function to halt bacterial dissemination throughout the tissue, by serving as a barrier to maintain containment within granuloma centers.