Isolation and High Throughput Flow Cytometric Apoptosis Assay of Human Neutrophils to Enable Compound Library Screening

Abstract

The study of human neutrophils in vitro is challenging due to their short half-life and propensity for activation. However, with careful handling and manipulation in the laboratory, they can be a powerful tool to investigate immune responses in health and disease. Here we describe a method for the isolation of human neutrophils from peripheral blood samples, followed by a high-throughput screen to assess the efficacy of a library of compounds in inducing neutrophil apoptosis, which may have therapeutic potential in neutrophil-driven diseases. This protocol is based on previously-published neutrophil isolation methods utilizing Dextran sedimentation of red blood cells followed by the separation of granulocytes with plasma/Percoll discontinuous gradient centrifugation. Yields of ~1 x 106 neutrophils per millilitre of blood, and purities of > 95% neutrophils are typical. Neutrophils are treated with a library of kinase inhibitors, followed by flow cytometry to assess the rate of neutrophil apoptosis. This protocol allows for the high-throughput screening of primary human immune cells to identify compounds with a potential to modify neutrophil function, and could be modified to assess other phenotypes if required.