Ex-vivo characterization of regulatory T cells in pulmonary tuberculosis patients, latently infected persons, and healthy endemic controls

The findings in this study showed that the association of Treg frequency with TB disease depends on the phenotypic markers used. While the frequency of CD4+CD25+/hi T cells was higher in TB patients compared to LTBI individuals, there was no difference in the frequency of CD4+CD25+FOXP3+CD127lo Treg among TB, LTBI, or EC. However, delineation of Tregs into active and naïve subsets revealed a significant increase in FOXP3 expression in active primed Tregs (CD4+CD25+FOXP3+CD127loCD45RO+Ki-67+) of TB patients compared to LTBI and EC; and a significantly higher frequency of resting primed (CD45RO+Ki-67−) Treg in QuantiFERON negative EC compared to TB patients. After treatment completion, there was a significant decline in the frequency of active primed Treg, median (IQR) from 12.4% (9.5-21.9) of Tregs to 9.3% (7.0-12.2); P = 0.003 Wilcoxon signed rank test. We conclude that Treg subsets may be differentially regulated and expressed in TB disease, cure, and infection.