Latent tuberculosis infection is associated with an increased frequency of Treg cells in the bronchoalveolar lavage

Background: A positive Interferon-γ release assay (IGRA+) after exposure to tuberculosis (TB) patients indicates a systemic immune response to M. tuberculosis (MTB). This condition defines latent infection with MTB (LTBI) and is associated with a higher risk of progression to active TB. However, only a minority of individuals has a positive IGRA-test result after exposure. Pulmonary clearance of MTB after infection may prevent a systemic immune response. In mice, pulmonary regulatory T-lymphocytes (T reg cells) can delay the clearance in early infection. In humans T reg cells are recruited to the site of infecti…