Antibodies, A Laboratory Manual, Second Edition, Edited by Edward A. Greenfield



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Assessment of Apoptosis (Programmed Cell Death)

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A simple multiplexed flow assay can be performed using Annexin V and propidium iodide. When cells enter apoptosis, phosphatidyl serine (PS) that is normally found on the inside of the cytoplasmic membrane is found on the extracellular surface of the membrane, thus revealing Annexin Vbinding sites. This is considered one of the early markers of apoptosis. Because binding of Annexin V to PS is calcium dependent, the buffers used for this assay must contain 1 mM calcium. The calcium dependence can also be used to test whether the Annexin V staining is specific. Thus, if the staining is performed in the presence of 1 mM EDTA, binding of Annexin V should be inhibited. The addition of propidium iodide to this stain allows subsequent stages of apoptosis and eventual cell death to be distinguished. For flow cytometry, this assay is best performed on suspension cells. Several kits that allow for assessment of as many as four measures of apoptosis by flow cytometry are commercially available.

Antibodies: A Laboratory Manual, Second edition
Antibodies: A Laboratory Manual, Second edition
Antibodies: A Laboratory Manual, Second edition

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