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Related Concept Videos

Complement System01:27

Complement System

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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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Selectins01:25

Selectins

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Cell adhesion is  an essential aspect of multicellularity. While stable cell interactions usually occur between cells of the same type, transient cell interactions occur between cells of different tissue types, such as between neutrophils and endothelial cells. Selectins are one class of cell adhesion molecules (CAMs) that bind carbohydrate ligands to form transient cell adhesion. They are rod-like proteins with a long extracellular part of variable length ending with the lectin domain,...
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Simple proteins and protein complexes contain only amino acids. In contrast, many other proteins, called conjugated proteins, covalently bond with non-protein moieties.
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Signaling cascades usually lack linearity. Multiple pathways interact and regulate one another, allowing cells to integrate and respond to diverse environmental stimuli.
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Receptor-mediated Endocytosis01:39

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Overview
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Receptor-mediated Endocytosis01:20

Receptor-mediated Endocytosis

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Receptor-mediated endocytosis is when bulk amounts of specific molecules are imported into a cell after binding to cell surface receptors. The molecules bound to these receptors are taken into the cell through inward folding of the cell surface membrane, which is eventually pinched off into a vesicle within the cell. Structural proteins, such as clathrin, coat the budding vesicle.
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Related Experiment Video

Updated: Oct 27, 2025

Author Spotlight: Advancing Antiviral Strategies Through Novel Immunocapture and Mass Spectrometry Techniques
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Author Spotlight: Advancing Antiviral Strategies Through Novel Immunocapture and Mass Spectrometry Techniques

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Lectin Pathway Mediates Complement Activation by SARS-CoV-2 Proteins.

Youssif M Ali1,2, Matteo Ferrari1, Nicholas J Lynch1

  • 1Department of Veterinary Medicine, School of Biological Sciences, University of Cambridge, Cambridge, United Kingdom.

Frontiers in Immunology
|July 22, 2021
PubMed
Summary
This summary is machine-generated.

The lectin pathway (LP) of the complement system activates during severe COVID-19. Targeting MASP-2, an LP enzyme, with inhibitors like Narsoplimab shows promise for treating critical illness.

Keywords:
COVID-19SARS-CoV-2complement systeminnate immunitylectin pathway

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Area of Science:

  • Immunology
  • Virology
  • Pathogenesis of Infectious Diseases

Background:

  • Complement system activation, particularly the lectin pathway (LP), is implicated in severe COVID-19 pathogenesis.
  • This activation drives a pro-inflammatory environment, endothelial injury, and acute respiratory distress syndrome (ARDS).
  • Current treatments like antivirals and corticosteroids are ineffective in advanced COVID-19 stages.

Purpose of the Study:

  • To investigate the role of the lectin pathway in SARS-CoV-2 infection.
  • To identify specific SARS-CoV-2 proteins involved in complement activation.
  • To evaluate the therapeutic potential of targeting the lectin pathway, specifically MASP-2, for severe COVID-19.

Main Methods:

  • Assessed binding of LP recognition molecules (MBL, FCN-2, CL-11) to SARS-CoV-2 S- and N-proteins.
  • Confirmed direct binding of SARS-CoV-2 N-protein to MASP-2 and subsequent complement activation.
  • Utilized a MASP-2 inhibitory monoclonal antibody to block LP activation.
  • Employed FACS analysis to quantify C3b deposition on cells expressing SARS-CoV-2 S protein.

Main Results:

  • Lectin pathway recognition molecules bind to SARS-CoV-2 S- and N-proteins, initiating complement activation.
  • SARS-CoV-2 N-protein directly binds and activates MASP-2, a key LP enzyme.
  • Inhibition of MASP-2 effectively blocks lectin pathway-mediated complement activation.
  • MASP-2 inhibition prevents C3b deposition on cells expressing SARS-CoV-2 S protein.

Conclusions:

  • The lectin pathway plays a significant role in the pathogenesis of severe COVID-19.
  • Targeting MASP-2 with inhibitors presents a promising therapeutic strategy for severe COVID-19.
  • Narsoplimab, a MASP-2 inhibitor, demonstrated potential in clinical trials for treating severe COVID-19.