Abstract
Regulation of specific immune responses following exposure to M. tuberculosis in humans and the role of regulatory T (Treg) cells in immune control of latent infection with M. tuberculosis are incompletely understood.
Latent infection was assayed by an Interferon-γ Release Assay (IGRA) in health care workers regularly exposed to tuberculosis patients and in household TB contacts in Germany. Immunophenotypes of bronchoalveolar lavage mononuclear cells and peripheral blood mononuclear cells (PBMC) were analysed by fluorescence activated cell sorting.
All tuberculosis contacts with latent infection (n=15) had increased (p<0.0001) frequencies of CD4+CD25+CD127- Treg cells (median 2.12%, InterQuartile Range -IQR- 1.63–3.01) among bronchoalveolar lavage (BAL) mononuclear cells compared to contacts (n= 25) with negative IGRA results (0.68%, IQR 0.32–0.96) No differences were seen when PBMC immunophenotypes of IGRA positive and negative TB contacts were compared (IGRA+: median 9.6%, IQR 5.9–10.1; IGRA-: median 7.7%, IQR 4.6–11.3; p=0.47). Five of 25 contacts with negative blood IGRA showed a positive IGRA from BAL cells, possibly indicating a limited local immune response.
In Germany, latent infection with M. tuberculosis, as defined by a positive M. tuberculosis-specific IGRA response on cells from the peripheral blood, is characterized by an increased frequency of Treg cells in the BAL.
- Bronchoalveolar lavage
- health care workers
- latent tuberculosis infection
- regulatory T cells
- tuberculosis
- tuberculosis exposure
- ERS