Dendritic Cells Are Decreased in Blood and Accumulated in Granuloma in Tuberculosis

Immunity against tuberculosis consists of innate and adaptive immune responses. In this study, we investigated the dynamics of dendritic cells (DC), which are known to elicit a variety of immune responses, in patients with tuberculosis. CD11c+ peripheral blood DC were decreased in patients with tuberculosis. Immunohistochemical analyses demonstrated that a number of fascin+, CD11c+, HLA-DR+ DC were infiltrating the lymphocyte areas of the tuberculous granulomas (tubercles). Immunohistochemical analyses also demonstrated that interferon-γ-producing Th1 cells were increased in the tubercles of the patients, indicating the presence of Th1 polarization at least in the context of inflammatory tissues. In vitro coculture of autologous naive T cells with CD11c+ or CD11c− DC pretreated with Bacillus Calmette Guérin augmented the production of Th1 cells. These findings suggested that the trafficking of DC from the peripheral blood into the tubercles causes a dominant Th1 balance and thus plays an essential role in the immunity against tuberculosis.