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Measuring the 50% Haemolytic Complement (CH50) Activity of Serum
08:26

Measuring the 50% Haemolytic Complement (CH50) Activity of Serum

Published on: March 30, 2010

Complement: activation, consequences, and control

K James

    The American Journal of Medical Technology
    |September 1, 1982
    PubMed

    Insights

    Complement activation drives immune-mediated injury through classical and alternative pathways. Control proteins modulate these potentially destructive effects, highlighting key mechanisms in host defense.

    Area of Science:

    • Immunology
    • Biochemistry

    Background:

    • Complement activation is a key humoral effector mechanism in immune-mediated injury.
    • Two primary pathways, classical and alternative, initiate complement cascades.
    • Both pathways involve sequential protein activation, with distinct dependencies on calcium and magnesium ions.

    Purpose of the Study:

    • To elucidate the mechanisms of complement activation via classical and alternative pathways.
    • To describe the protein interactions and dependencies within each pathway.
    • To highlight the role of control proteins in modulating complement's effects.

    Main Methods:

    • Review of established complement pathway activation sequences.
    • Analysis of biochemical dependencies (e.g., calcium, magnesium) for key steps.
    • Identification of common and distinct proteins in classical and alternative pathways.

    Main Results:

    • Classical pathway activation initiated by antigen-antibody reaction involves C1q, C1r, C1s (calcium-dependent) and C4, C2 (magnesium-dependent).
    • Alternative pathway activation is surface-dependent, involving C3b and Factor B (magnesium-dependent), leading to C3 convertase formation.
    • Both pathways converge, activating nine proteins, with six common to both.

    Conclusions:

    • Complement activation, while crucial for host defense, can lead to immune-mediated injury.
    • Control proteins play a vital role in regulating the extent of complement activation and its potentially harmful consequences.

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