Myeloid-derived Suppressor Cell and Non-classical Monocyte Frequencies Are Directly Related to the Immunological Status of Patients With Active Tuberculosis

Alterations of myeloid cell populations have been reported in patients with tuberculosis (TB). Since myeloid-derived suppressor cells (MDSC) and non-classical monocytes (CD14 + CD16 + ) seem to play an important role in TB, we studied the relationship between these cells and the immunological status of patients. TB patients were classified as high responders (HR-TB) or low responders (LR-TB) according to their T cell responses against a whole cell lysate of Mycobacterium tuberculosis ( Mtb -Ag). Thus, LR-TB, individuals with severe disease, display a weaker immune response to Mtb compare to HR-TB, subjects with strong immunity against the bacteria. We observed that LR-TB presented higher percentages of CD14 + CD16 + monocytes as compared to HR-TB and healthy donors (HD). Moreover, monocyte-like (M-MDSC) and polymorphonuclear-like MDSC (PMN-MDSC) were increased in TB patients as compared to HD. Furthermore, the proportion of M-MDSC of TB patients inversely correlated with the levels of IFN-γ released after Mtb -Ag stimulation. We also found that LR-TB displayed the highest levels of circulating M-MDSC. Interestingly, in LR-TB, the frequencies of non-classical monocytes and M-MDSC were restored after only three weeks of anti-TB treatment. Together, our findings show a direct relationship between the immunological status of TB patients and the levels of different circulating myeloid cell populations.