Expression and clinical significance of B and T lymphocyte attenuator on CD4+ and CD8+ T cells from patients with pulmonary tuberculosis

Background: As an immune checkpoint, upregulation of B and T lymphocyte attenuator (BTLA) contributes to T-cell exhaustion in chronic infection. However, the characteristics of BTLA on T cells of patients with pulmonary tuberculosis (PTB) are still uncovered. Aims: The aim of the study was to elucidate the dynamics and clinical significance of BTLA expression on circulating CD4(+) and CD8(+) T cells of PTB patients. Materials and Methods: BTLA expression on T cells from PTB patients with smear positivity (n = 86) and healthy controls (HCs) (n = 40) were determined using flow cytometry. Results: The levels of BTLA expression on circulating CD4(+) and CD8(+) T cells of PTB patients with smear positivity were both upregulated, compared with HC. At the same time, the levels of BTLA expression on CD4(+) and CD8(+) T cells of patients with retreatment were both higher than that of those with initial treatment and gradually upregulated along with the increase of the bacillary load in sputum. In addition, the patients with lung cavity were discovered to present higher levels of BTLA expression on CD4(+) and CD8(+) T cells than those without lung cavity. Whereas we noted that there was no correlation between the levels of BTLA expression and the positivity or negativity of anti-Mycobacterium tuberculosis antibody. Conclusions: The levels of BTLA expression were upregulated on CD4(+) and CD8(+) T cells of PTB patients and associated with disease progression. Thereby, BTLA expression on T cells may be considered as a potential clinical indicator and utilized as a therapeutic target for PTB.