Abstract
The possibility that CD4(+) T cells can act as "innate-like" cells to contain very early Mycobacterium tuberculosis dissemination and function as master helpers to sustain multiple effector functions of CD8(+) T cells and CD3(-) lymphocytes during development of adaptive immunity against primary tuberculosis (TB) has not been demonstrated. We showed that pulmonary M. tuberculosis infection of CD4-depleted macaques surprisingly led to very early extrapulmonary M. tuberculosis dissemination, whereas CD4 deficiency clearly resulted in rapid TB progression. CD4 depletion during M. tuberculosis infection revealed the ability of CD8(+) T cells to compensate and rapidly differentiate to Th17-like/Th1-like and cytotoxic-like effectors, but these effector functions were subsequently unsustainable due to CD4 deficiency. Whereas CD3(-) non-T lymphocytes in the presence of CD4(+) T cells developed predominant Th22-like and NK-like (perforin production) responses to M. tuberculosis infection, CD4 depletion abrogated these Th22-/NK-like effector functions and favored IL-17 production by CD3(-) lymphocytes. CD4-depleted macaques exhibited no or few pulmonary T effector cells constitutively producing IFN-γ, TNF-α, IL-17, IL-22, and perforin at the endpoint of more severe TB, but they presented pulmonary IL-4(+) T effectors. TB granulomas in CD4-depleted macaques contained fewer IL-22(+) and perforin(+) cells despite the presence of IL-17(+) and IL-4(+) cells. These results implicate a previously unknown innate-like ability of CD4(+) T cells to contain extrapulmonary M. tuberculosis dissemination at very early stage. Data also suggest that CD4(+) T cells are required to sustain multiple effector functions of CD8(+) T cells and CD3(-) lymphocytes and to prevent rapid TB progression during M. tuberculosis infection of nonhuman primates.