Human peripheral neutrophils express functional IL-21 receptors.

Neutrophils play key roles in the inflammatory response. The IL-21 cytokine and receptor system is known to be involved in various inflammatory diseases. However, the direct action of IL-21 on neutrophils has not been reported. Here, we show that human neutrophils in peripheral blood express functional IL-21 receptors (IL-21Rs). Expression of the IL-21Rα chain (IL-21Rα) was reduced following various treatments to remove red blood cells, including hypotonic shock, ammonium chloride-mediated lysis, and Percoll density centrifugation. Thus, we utilized whole blood flow cytometric assays to investigate the neutrophil responses to IL-21. IL-21 upregulated the surface expression of CD11b and CD16 on neutrophils and augmented the neutrophils' phagocytic ability. Our data indicated that IL-21 has the potential to enhance the neutrophil functions.