Programmed death-ligand 1 correlates with acute influenza B virus infection.

Programmed Death-Ligand 1 (PD-L1) has been proven to mediate various mechanisms to induce T-cell dysfunction in influenza A virus infection. However, whether PD-L1 similarly contributes to inflammatory responses during influenza B virus (IBV) infection remains unknown. Here we investigated PD-L1 expression patterns during acute IBV infection. A total of 24 IBV-infected patients and 33 healthy controls were recruited and assigned to three age subgroups. Using flow cytometry, we assessed PD-L1 expression on circulating leukocytes and measured the concentrations of plasma cytokines. Our findings demonstrated that IBV infection induced PD-L1 expression on human dendritic cells, T-cells and monocytes. Additionally, IL-2, IL-4, IL-6, IL-10, and TNF concentrations elevated significantly, indicating the occurrence of robust inflammatory responses. Notably, age did not influence PD-L1 expression on peripheral immune cells across the three age subgroups. These results reveal that IBV infection involves the expression of PD-L1 on key immune cell populations, and PD-L1 may serve as a target in the design of new therapeutic strategies for IBV.