Identification of CD244-expressing myeloid-derived suppressor cells in patients with active tuberculosis.

Development of active TB is accompanied by immune suppression and the underlining mechanisms have been explored extensively in recent years. MDSCs are a heterogeneous group of immature and progenitor myeloid cells with strong immunosuppressive ability for both natural and adaptive immunity. In our analysis of CD244 (2B4)-expressing cells in PBMCs from patients with active TB, a CD3(-)CD244(high) subpopulation was identified. A match of cell population in flow cytometry showed that nearly all CD3(-)CD244(high) cells were CD3(-)HLA-DR(-)CD11b(int)CD33(+) cells. The CD3(-)CD244(high) cell population has phenotypes of CD3(-)CD19(-)CD56(-)CD15(-)CD66b(-)CD33(+)CD11b(+)CD14(-)HLA-DR(neg/low), which was consistent with MDSCs in humans as previously reported. Patients with active TB had higher frequencies of CD3(-)CD244(high) cells as compared with healthy controls. The CD3(-)CD244(high) cell population had high levels of NOS2 expression and was negatively correlated with activation and effective molecule production of CD4(+) and CD8(+) T cells. In conclusion, CD3(-)CD244(high) cells had phenotypes of MDSCs and CD244 might be used as a marker for human CD3(-)HLA-DR(-)CD11b(int)CD33(+) MDSCs.