NOS2 and infection: The presence of abundant neutrophilic infiltrates in the brain of Nos2−/− mice may be due to the inability of Nos2−/− macrophages to contain the M.tb infection, as NOS2 upregulation by murine macrophages has been shown to be implicated in M.tb killing [22], which may result in the activation and recruitment of more leukocytes to the site of infection [28].