CD4(+)FoxP3(+) T regulatory cells in drug-susceptible and multidrug-resistant tuberculosis

Regulatory T cells (Treg) increase in active tuberculosis (TB). However, whether Treg-mediated immune suppression affect the susceptibility to active TB or development of multidrug-resistant (MDR) TB is not yet clear. We compared circulatory Treg frequencies in drug susceptible (DS) and MDR TB before and after anti-TB treatment. Circulatory Treg frequencies were measured in blood samples from 33 DS TB, 7 mycobacterial culture-positive active MDR TB, 16 stable MDR TB who had been culture negative for at least 6 months, and 14 healthy controls before and after treatment. Treg frequency was measured by flow cytometry using cell-surface marker CD4 and intracellular marker FoxP3. Treg frequency was higher in DS TB and active MDR TB patients than in healthy controls (p < 0.05), with no significant difference between the former. Treg frequency was higher in patients with sputum acid-fast bacilli smear-positive TB than in patients with smear-negative TB, but the increase did not correlate with the radiologic extent of TB or presence of a cavity. After successful treatment, Treg decreased to control levels in DS TB and MDR TB patents. The pattern of change, in which Treg frequency increased during active infection and normalized to control levels after successful treatment, was similar in DS and MDR TB patients.