Lymphoid function of the tuberculous granuloma

Induced lymphoid structures associated with pulmonary granulomas have been observed during TB in both humans and mice and could orchestrate host defense. In order to determine whether granulomas perform lymphoid functions, mice lacking secondary lymphoid organs (SLOs) were infected with Mycobacterium tuberculosis (MTB). As in wild type mice (WT), granulomas developed, MTB was controlled, and antigen-specific T cell responses including T central memory (TCM) cells were generated in the complete absence of SLOs. Moreover, T cell activation correlated with granuloma formation in these mice and TCM cells accumulated in lungs and participated in protection against secondary MTB infection. Lung granulomas may therefore represent tertiary lymphoid organs (TLOs) capable of priming robust T cell responses and mediating host defense during chronic MTB at the site of infection. 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.