Journal of visualized experiments : JoVEMay 29, 2023

Measuring Neutrophil DNA-Protein Complexes Released During Immune Response Using an Improved Test

Updated Jan 17, 2026

Abstract

Plasma concentrations of MPO-DNA and NE-DNA were significantly higher in 16 patients with COVID-19 than in healthy controls.

Neutrophils release NETs in response to certain stimuli, forming web-like structures composed of DNA and proteins.
A modified sandwich enzyme-linked immunosorbent assay measures specific components of NETs, namely MPO-DNA and NE-DNA complexes.
The assay demonstrated good linearity and high precision in measuring NET components.
Significantly elevated levels of MPO-DNA and NE-DNA in COVID-19 patients with acute respiratory distress syndrome suggest increased NET formation.

Simplified

Certain stimuli, such as microorganisms, cause neutrophils to release neutrophil extracellular traps (NETs), which are basically web-like structures composed of DNA with granule proteins, such as myeloperoxidase (MPO) and neutrophil elastase (NE), and cytoplasmic and cytoskeletal proteins. Although interest in NETs has increased recently, no sensitive, reliable assay method is available for measuring NETs in clinical settings. This article describes a modified sandwich enzyme-linked immunosorbent assay to quantitatively measure two components of circulating NETs, MPO-DNA and NE-DNA complexes, which are specific components of NETs and are released into the extracellular space as breakdown products of NETs. The assay uses specific monoclonal antibodies for MPO or NE as the capture antibodies and a DNA-specific detection antibody. MPO or NE binds to one site of the capture antibody during the initial incubation of samples containing MPO-DNA or NE-DNA complexes. This assay shows good linearity and high inter-assay and intra-assay precision. We used it in 16 patients with COVID-19 with accompanying acute respiratory distress syndrome and found that the plasma concentrations of MPO-DNA and NE-DNA were significantly higher than in the plasma obtained from healthy controls. This detection assay is a reliable, highly sensitive, and useful method for investigating the characteristics of NETs in human plasma and culture supernatants.

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Measuring Neutrophil DNA-Protein Complexes Released During Immune Response Using an Improved Test

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