Tuberculosis (TB) is a major global public health problem causing large number of deaths, even more than any another single infection disease. Regulatory T cells (Treg) are naturally involved in suppression of the immune response; however, their role in tuberculosis is unknown. FOXP3 has been identified as a specific marker for Treg activity, and it is required for T cells development and function. To understand the mechanisms involved in the control of Th1 response during TB infection is critical to shed light into aspects that limit the excessive inflammation and lung lesions in TB. The aim of this work was to determine the frequency of regulatory T cells in patients with pulmonary and pleural tuberculosis.
Twenty four patients with pulmonary, and 10 with pleural tuberculosis were evaluated for CD4+CD25hi+ and FOXP3 expression on peripheral blood and pleural effusion. Latently infected contacts were used as control, and the percentage of Treg cells were evaluated by flow cytometry.
Patients with TB exhibit higher level of median FOXP3 than controls (2.37 vs 1.12; p = 0.0009). The level of CD4+CD25hi+ also is increased in TB group (p = 0.0051). Most remarkably, the expression of median CD4+CD25hi+ was especially more elevated in pleural effusion than blood (0.3 vs 0.02; p = 0.002). Level of median FOXP3 also is higher in pleural effusion (0.5 vs 0.1; p = 0.0020). Control group has lower level of both markers (p < 0.05).
We considered that patients with active TB would have higher frequencies of Treg than latently infected contacts, and that cells infiltrated the pleural compartment are, in fact, T regulatory as express high frequency of FOXP3. These cells are in high frequency in patients with tuberculosis suggesting important role in TB immunoregulation.
Measurement of regulatory T cells may offer a noninvasive means of improving diagnostic test to differentiate latent and acute infection with M. tuberculosis.
Denise Rodrigues, No Financial Disclosure Information; No Product/Research Disclosure Information