Expression of PD-1/PD-L1 in children with tuberculosis
Objective 
To investigate the expression of programmed death 1 (PD-1) and programmed death-ligand 1 (PD-L1) at mRNA level in children (≤5 years old) with tuberculosis (TB) and to investigate their roles in the development of childhood tuberculosis. 
 
 
Methods 
Peripheral blood samples were collected from 36 children with tuberculosis(TB) and 20 healthy children (≤5 years old). The peripheral blood mononuclear cells (PBMC) were isolated from the blood samples by using lymphocyte separation liquid. Real-time fluorescence quantitative PCR was performed to measure the expression of PD-1 and PD-L1 at mRNA level. 
 
 
Results 
The expression of PD-1 and PD-L1 at transcriptional level in the peripheral blood of children with pulmonary or extrapulmonary TB were increased as compared with those in healthy children (P<0.05). A more significant increase was observed in the expression of PD-L1 at mRNA level. 
 
 
Conclusion 
This study suggested that the expression of PD-1 and PD-L1 at mRNA level were increased in the peripheral blood of children (≤5 years old) with pulmonary or extrapulmonary TB, indicating that PD-1/PD-L1 might play a very important role in the pathogenesis of childhood tuberculosis. 
 
 
Key words: 
Tuberculosis; Children; Programmed death 1; Programmed death-ligand 1