A Sensitive Immunochemical Assay for Measuring the Concentration of the Activated Protein C-protein C Inhibitor Complex in Plasma:

Karin Strandberg; Margareta Kjellberg; Richard Knebel; Hans Lilja; Johan Stenflo

doi:10.1055/s-0037-1616093

Thrombosis and Haemostasis, Inhaltsverzeichnis

Thromb Haemost 2001; 86(02): 604-610
DOI: 10.1055/s-0037-1616093

Review Article

Schattauer GmbH

A Sensitive Immunochemical Assay for Measuring the Concentration of the Activated Protein C-protein C Inhibitor Complex in Plasma:

Use of a Catcher Antibody Specific for the Complexed/Cleaved Form of the Inhibitor

Karin Strandberg^*

¹Department of Clinical Chemistry, University Hospital, Malmö, Lund University, Malmö, Sweden

,

Margareta Kjellberg^*

¹Department of Clinical Chemistry, University Hospital, Malmö, Lund University, Malmö, Sweden

,

Richard Knebel

²Department of Orthopedic Surgery, University Hospital, Malmö, Lund University, Malmö, Sweden

,

Hans Lilja

¹Department of Clinical Chemistry, University Hospital, Malmö, Lund University, Malmö, Sweden

,

Johan Stenflo

¹Department of Clinical Chemistry, University Hospital, Malmö, Lund University, Malmö, Sweden

› Institutsangaben

Abstract

Summary

Activated protein C (APC) is a serine proteinase that regulates blood coagulation. In plasma it is inhibited mainly by the protein C inhibitor (PCI). The plasma concentrations of APC-PCI complex is increased in hypercoagulative states such as deep venous thrombosis. Formation of the APC-PCI complex induces a drastic conformational change in PCI that exposes new epitopes (neoepitopes) on the molecule. We have devised a simple immunofluorometric sandwich assay for measurements of the concentrations of APC-PCI complex, employing as the catcher, a monoclonal antibody that has a high affinity (K_D ≈ 4 × 10^-11M) for a complexation-specific neoepitope that is expressed on PCI. A monoclonal antibody against protein C is employed as the tracer. The method gives a linear dose-response curve (0.06-50 πg/l), has a low detection limit (0.06 πg/l) and no crossreactivity with native PCI at physiologic plasma concentrations. We have now determined the concentration of the APC-PCI complex in healthy individuals.

Keywords

APC-PCI complex - immunochemical assay - hypercoagulability

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