Measurement of phosphatidylserine exposure during storage of platelet concentrates using the novel probe lactadherin: a comparison study with annexin V

Authors

  • Abdul-Majeed Albanyan,

    1. From the Nuffield Department of Clinical Medicine, University of Oxford, the National Blood Service, John Radcliffe Hospital, and the Oxford Haemophilia & Thrombosis Centre, Churchill Hospital, Oxford, UK; and the Protein Chemistry Laboratory, Department of Molecular Biology, University of Aarhus, Aarhus, Denmark.
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  • Michael F. Murphy,

    1. From the Nuffield Department of Clinical Medicine, University of Oxford, the National Blood Service, John Radcliffe Hospital, and the Oxford Haemophilia & Thrombosis Centre, Churchill Hospital, Oxford, UK; and the Protein Chemistry Laboratory, Department of Molecular Biology, University of Aarhus, Aarhus, Denmark.
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  • Jan T. Rasmussen,

    1. From the Nuffield Department of Clinical Medicine, University of Oxford, the National Blood Service, John Radcliffe Hospital, and the Oxford Haemophilia & Thrombosis Centre, Churchill Hospital, Oxford, UK; and the Protein Chemistry Laboratory, Department of Molecular Biology, University of Aarhus, Aarhus, Denmark.
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  • Christian W. Heegaard,

    1. From the Nuffield Department of Clinical Medicine, University of Oxford, the National Blood Service, John Radcliffe Hospital, and the Oxford Haemophilia & Thrombosis Centre, Churchill Hospital, Oxford, UK; and the Protein Chemistry Laboratory, Department of Molecular Biology, University of Aarhus, Aarhus, Denmark.
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  • Paul Harrison

    1. From the Nuffield Department of Clinical Medicine, University of Oxford, the National Blood Service, John Radcliffe Hospital, and the Oxford Haemophilia & Thrombosis Centre, Churchill Hospital, Oxford, UK; and the Protein Chemistry Laboratory, Department of Molecular Biology, University of Aarhus, Aarhus, Denmark.
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Abdul-Majeed Albanyan, Oxford Haemophilia & Thrombosis Centre, Churchill Hospital, Oxford, OX3 7LJ, UK; e-mail: abdul.albanyan@ndm.ox.ac.uk.

Abstract

BACKGROUND: Annexin V binding to platelets (PLTs) is considered the gold standard for monitoring phosphatidylserine (PS) exposure. However, recent comparison of annexin V with the new calcium-independent PS probe lactadherin revealed that annexin V requires a certain threshold of PS exposure (2%-8%) for binding to occur. The aim of this study was to compare annexin V and lactadherin labeling of PLTs in PLT concentrates (PCs).

STUDY DESIGN AND METHODS: Optimal labeling conditions for lactadherin and annexin V were established and then compared in either resting or calcium ionophore (CI)-activated PLTs from normal whole blood. Furthermore, 40 PCs (20 apheresis-derived and 20 pooled buffy coat–derived) were stored under standard blood bank conditions and PLT activation was monitored by measuring PS exposure with annexin V and lactadherin along with CD42b, CD61, and CD62P by flow cytometry on Days 1, 3, 5, and 7.

RESULTS: Lactadherin reported a higher exposure of PS than did annexin V in normal PLTs at submaximal doses of CI. PLTs from both types of concentrate, as expected, demonstrated evidence of increased activation during storage using annexin V, lactadherin, CD42b, or CD62P. However, a significantly higher percentage of PS-positive PLTs was found with lactadherin than annexin V.

CONCLUSION: PS exposure on the surface of stored PLTs has been previously underestimated due to the wide use of annexin V. Lactadherin provides a truer reflection of the degree of PS exposure and offers a new calcium-independent approach to studying PLT activation and/or apoptosis.

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