Abstract
BACKGROUND: T cell lymphopenia was a significant characteristic of severe influenza infection and it was associated with the functional changes of T cells. It is necessary to clarify the T cells characteristics of kinetic changes and their correlation with disease severity. METHODS: In a cohort of hospitalized influenza patients with varying degrees of severity, we characterized lymphocyte populations using flow cytometry. RESULTS: The numbers of cycling (Ki67(+)) T cells at the acute phase of severe influenza were higher, especially in the memory (CD45RO(+)) T cell subsets. T cells from hospitalized influenza patients also had significantly higher levels of the exhausted marker PD-1. Cycling status of T cells was associated with T cell activation during the acute phase of influenza infection. The recruitment of cycling and activated (CD38(+)HLA-DR(+)) CD8(+) T cells subset is delayed in severe influenza patients. CONCLUSIONS: The increased numbers of cycling memory (Ki67(+)CD45RO(+)) T cells subsets and delayed kinetics of activated (CD38(+)HLA-DR(+)) CD8(+) T cells, could serve as possible biological markers for disease severity.