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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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Extrinsic and Intrinsic Pathways of Hemostasis01:20

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Blood clotting or coagulation involves extrinsic and intrinsic pathways, which ultimately merge into the common pathway, forming a fibrin clot.
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Hemostasis is a crucial process that prevents excessive blood loss from damaged blood vessels. It involves various mechanisms such as vasoconstriction, platelet adhesion and activation, and fibrin formation. The importance of each mechanism depends on the type of vessel injury. In contrast, thrombosis is the abnormal formation of a blood clot within the blood vessels, leading to potential complications if the clot obstructs blood flow. Thrombosis can be caused by increased coagulability of the...
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Coagulation01:09

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The coagulation phase is a critical part of the body's process to prevent blood loss following injury to blood vessels. It involves chemical reactions that form a clot to seal the injured area. The clotting process begins shortly after injury, within 15-20 seconds for severe damage and 1-2 minutes for minor injuries.
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Coagulation01:06

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Colloidal solids are solid particles suspended in solution. They are usually negatively charged, attracting a compact primary layer of positively charged ions, which attract more counterions to form an electrical double layer. Electrostatic repulsion between the charged double layers prevents the particles from colliding, stabilizing the colloids. These solids are often undesirable because they can contain toxins that are difficult to remove. Coagulation is a technique that helps aggregate and...
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Clot Retraction and Fibrinolysis01:16

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After a fibrin clot is formed, the next step is clot retraction, a vital process facilitated by platelet contractile proteins, such as actin and myosin. These proteins pull the fibrin strands closer together and condense the clot. This action reduces the size of the clot, creating a smaller, denser structure that effectively seals off the damaged vessel. Clot retraction consolidates the clot and helps with wound healing by bringing the edges of the damaged blood vessel closer together.
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Measurement of Factor V Activity in Human Plasma Using a Microplate Coagulation Assay
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Measurement of Factor V Activity in Human Plasma Using a Microplate Coagulation Assay

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Complement component factor B has thrombin-like activity.

Kazue Takahashi1, Nirmal K Banda2, V Michael Holers2

  • 1Department of Pediatrics, Massachusetts General Hospital and Harvard Medical School, Boston, MA, 02114, United States.

Biochemical and Biophysical Research Communications
|March 19, 2021
PubMed
Summary
This summary is machine-generated.

This study reveals that complement factor B (Bf), part of the alternative complement pathway, possesses thrombin-like activity. This finding highlights a new link between complement and coagulation systems in innate immunity.

Keywords:
Coagulation diseasesComplement factor BInfectious diseasesMBL-Associated serine protease (MASP)Serine proteasesThrombinTrypsin-like domain

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Area of Science:

  • Biochemistry
  • Immunology
  • Molecular Biology

Background:

  • Serine proteases are crucial for innate immunity, found in the coagulation and complement pathways.
  • Dysregulation of these pathways can lead to various diseases, including coagulation disorders and infections.
  • Previous research indicated connections between coagulation and complement systems.

Purpose of the Study:

  • To investigate novel functional roles of complement component factor B (Bf).
  • To explore the relationship between the alternative complement pathway and coagulation.
  • To identify potential therapeutic targets by understanding cross-talk between immune pathways.

Main Methods:

  • Bioinformatic analysis of serine protease domains.
  • Biochemical assays to determine enzymatic activity.
  • Comparative sequence analysis of factor B, thrombin, and Limulus clotting factor C.

Main Results:

  • Complement factor B (Bf) exhibits thrombin-like enzymatic activity.
  • The trypsin-like domain of Bf shows homology to thrombin.
  • Bf's trypsin-like domain is also related to Limulus clotting factor C, an LPS-sensitive factor.

Conclusions:

  • Factor B possesses a previously unrecognized enzymatic function with implications for innate immunity.
  • This finding suggests a direct enzymatic link between the complement and coagulation cascades.
  • Further research into Bf's activity may reveal new insights into disease mechanisms and treatments.