B cell infiltration is associated with the increased IL-17 and IL-22 expression in the lungs of patients with tuberculosis.

Although it has been recognized that ectopic follicle-like B cell aggregate formation is common in the lungs of patients with tuberculosis, the role of infiltrated B cells in human tuberculosis remains to be elucidated. In the present study, we showed that ectopic B cell aggregate formation was associated with containment of Mycobacterium tuberculosis. The area ratio of ectopic B cell aggregates was correlated with localized IL-17 mRNA expression and peripheral TGF-β and IL-6 mRNA expression. Depletion of B cells from pleural fluid mononuclear cells resulted in significantly diminished M. tuberculosis antigen-specific IL-17 and IL-22 production, but not in IFN-γ secretion. Therefore, ectopic lung B cell formation is important for containment of M. tuberculosis, and up-regulation of IL-17 and IL-22 responses may be an important mechanism underlying the protective role B cells in human tuberculosis.