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Complement System

Complement System

The complement system is a group of approximately 20 plasma proteins that strengthen the body's defenses against infections through opsonization, inflammation, and cell lysis. Opsonization involves coating pathogens with complement proteins, making them more recognizable and facilitating phagocyte engulfment. Certain complement proteins induce inflammation that attracts immune cells to the site of infection. Cell lysis involves the destruction of pathogens through the formation of a...

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Related Experiment Video

Updated: Jun 13, 2025

Real-Time, High-Throughput Microscopic Quantification of Human Neutrophil Extracellular Trap Release and Assessing the Pharmacology of Antagonists

Real-Time, High-Throughput Microscopic Quantification of Human Neutrophil Extracellular Trap Release and Assessing the Pharmacology of Antagonists

Published on: October 18, 2024

Complement-Mediated Two-Step NETosis: Serum-Induced Complement Activation and Calcium Influx Generate NADPH

Maria Maqsood¹, Samuel Suntharalingham¹, Meraj Khan²

¹Cell Biology, Research Institute, Peter Gilgan Centre for Research and Learning, The Hospital for Sick Children, Toronto, ON M5G 1X8, Canada.

International Journal of Molecular Sciences

|September 14, 2024

Summary

This summary is machine-generated.

Complement activation primes neutrophils for NETosis in serum, but requires serum-free conditions and NADPH oxidase for NET formation. This two-step process is key to understanding innate immunity.

Keywords:

NET formation NETosis P-selectin/CD11b citrullinated histone 3 complement neutrophils

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Last Updated: Jun 13, 2025

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Morphological and Compositional Analysis of Neutrophil Extracellular Traps Induced by Microbial and Chemical Stimuli

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Simplified Human Neutrophil Extracellular Traps NETs Isolation and Handling

Simplified Human Neutrophil Extracellular Traps NETs Isolation and Handling

Published on: April 16, 2015

Area of Science:

Immunology
Cell Biology

Background:

The complement system and neutrophils are vital components of innate immunity.
Neutrophil extracellular traps (NETs) are crucial for immune defense but their formation mechanisms are not fully understood.
Complement-mediated NETosis is a key area requiring further elucidation.

Purpose of the Study:

To investigate the mechanisms of complement-mediated neutrophil extracellular trap (NET) formation.
To test a proposed two-step model for NETosis involving complement activation and subsequent NET release.

Main Methods:

Utilized neutrophils from healthy donors and endothelial cells.
Employed assays such as Fluo-4AM, DHR123, and SYTOX.
Applied flow cytometry and confocal microscopy for analysis.

Main Results:

Complement activation upregulated complement regulators (CD46, CD55, CD59) and CD11b on neutrophils, enhancing endothelial cell attachment.
Complement activation induced calcium influx and histone H3 citrullination (CitH3), but CitH3 alone did not trigger NET formation.
NET formation was dependent on serum-free conditions and NADPH oxidase-driven reactive oxygen species (ROS) production.

Conclusions:

Complement-mediated NET formation is a two-step process: priming in serum followed by NET completion in serum-free conditions.
The priming step involves complement deposition, neutrophil activation, calcium influx, CitH3 formation, and endothelial cell attachment.
The completion step requires NADPH-dependent ROS production for NET release.
This understanding may identify therapeutic targets for diseases involving complement activation and NETosis.