The association between serum miR-155 and natural killer cells from tuberculosis patients.

Tuberculosis (TB) is still an infectious disease that greatly threatens human health, and is always refractory to the current therapeutic modalities. Accumulated evidence revealed that microRNAs (miRNAs) are closely with various pathologies, such as TB. The possibilities of miRNAs as diagnostic biomarkers and therapeutic targets have been proved. However, it is still unknown if miRNA is implicated in the TB-associated immunity. This study revealed that miR-155, which has been shown to suppress the activation of natural killer (NK) cells associated with tumors, was downregulated in serum samples of TB patients (n=90), compared with healthy controls (n=31). Cytotoxicity assays indicated that NK cells, which have been demonstrated to promote TB progression, exhibited lower cytotoxicity in high serum miR-155 TB patients (n=37). There is an inverse relationship between serum miR-155 abundance and NK cell cytotoxicity (R=-0.659, P=0.000). Further studies demonstrated that miR-155 level is inversely associated with the concentration of TNFα secreted by NK cells from TB patients (n=37, R=-0.694, P=0.000). Collectively, serum miR-155 level was shown to be negatively associated with the TB-suppressing activity of NK cells, and this miRNA can be used as a potential therapeutic agent for TB treatment.