Cytolytic CD8+ T Cells Recognizing CFP10 Are Recruited to the Lung after Mycobacterium tuberculosis Infection

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Abstract
Optimum immunity against Mycobacterium tuberculosis requires both CD4+ and CD8+ T cells. In contrast with CD4+ T cells, few antigens are known that elicit CD8+ T cells during infection. CD8+ T cells specific for culture filtrate protein-10 (CFP10) are found in purified protein derivative positive donors, suggesting that CFP10 primes CD8+ T cells in vivo. Using T cells from M. tuberculosis–infected mice, we identified CFP10 epitopes recognized by CD8+ T cells and CD4+ T cells. CFP10-specific T cells were detected as early as week 3 after infection and at their peak accounted for up to 30% of CD8+ T cells in the lung. IFNγ-producing CD8+ and CD4+ T cells recognizing CFP10 epitopes were preferentially recruited to the lungs of M. tuberculosis–infected mice. In vivo cytolytic activity of CD8+ T cells specific for CFP10 and TB10.3/10.4 proteins was detected in the spleen, pulmonary lymph nodes, and lungs of infected mice. The cytolytic activity persisted long term and could be detected 260 d after infection. This paper highlights the cytolytic function of antigen-specific CD8+ T cells elicited by M. tuberculosis infection and demonstrates that large numbers of CFP10-specific cytolytic CD8+ T cells are recruited to the lung after M. tuberculosis infection.