The elevated expression of LAG-3 on CD8+T cells correlates with disease severity of pulmonary TB

Objective Lymphocyte-activation gene 3 (LAG-3) plays an important role in regulating T-cell responses and inducing peripheral tolerance. Our aim in this study was to investigate the relationship between LAG-3 and active tuberculosis (ATB) and the impact of LAG-3 blockade on CD8 + T cells. Methods Flow cytometry was used to detect the expression of LAG-3 on CD4 + T and CD8 + T cells in the peripheral blood and bronchoalveolar lavage fluid from ATB patients and to explore the relationship between LAG-3 and ATB. Results The expression of LAG-3 on CD4 + T and CD8 + T cells in ATB patients was increased (P + T cells with high expression of LAG-3 were associated with sputum culture results (P + T cells and the severity of tuberculosis and found that the expression of LAG-3 on CD8 + T cells in smear-positive tuberculosis patients was significantly higher than that in sputum smear-negative tuberculosis patients (P + T cells was negatively correlated with the presence of lung lesions (P + T cells was also upregulated, and LAG-3-expressing CD8 + T cells showed reduced production of IFN-γ, decreased activation, and lower proliferation, while the function of CD8 + T cells was restored when LAG-3 signaling was blocked. Conclusions This study further explored the relationship between immune exhaustion caused by LAG-3 and immune escape of Mycobacterium tuberculosis and revealed that the elevated expression of LAG-3 on CD8 + T cells correlates with functional defects of CD8 + T cells and the severity of pulmonary TB.