Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 105, Issue 31, Pages 10961-10966Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0801496105
Keywords
priming; transgenic mice
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Funding
- NIAID NIH HHS [R01AI47963, AI-55500, R01 AI047963, AI-67723, R01 AI067723, R01 AI055500, P01 AI046530, AI-46530] Funding Source: Medline
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CD4(+) T cell responses to aerosol Mycobacterium tuberculosis (Mtb) infection are characterized by the relatively delayed appearance of effector T cells in the lungs. This delay in the adaptive response is likely critical in allowing the bacteria to establish persistent infection. Because of limitations associated with the detection of low frequencies of naive T cells, it had not been possible to precisely determine when and where naive antigen-specific T cells are first activated. We have addressed this problem by using early secreted antigenic target 6 (ESAT-6)-specific transgenic CD4 T cells to monitor early T cell activation in vivo. By using an adoptive transfer approach, we directly show that T cell priming to ESAT-6 occurs only after 10 days of infection, is initially restricted to the mediastinal lymph nodes, and does not involve other lymph nodes or the lungs. Primed CD4 T cells rapidly differentiated into proliferating effector cells and ultimately acquired the ability to produce IFN-gamma and TNF-alpha ex vivo. Initiation of T cell priming was enhanced by two full days depending on the magnitude of the challenge inoculum, which suggests that antigen availability is a factor limiting the early CD4 T cell response. These data define a key period in the adaptive immune response to Mtb infection.
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