6 Questions
What is the result of inserting the 'membrane attack complex' into the cell membrane of target cells?
Disruption of the cell membrane leading to lysis
What role does C3b play in the immune response?
Coats cells and antigen-antibody complexes for better phagocytosis
Which components are known as 'anaphylatoxins'?
C3a, C4a, C5a
Which complement component specifically activates and attracts neutrophils and macrophages?
C5a
Which pathway of complement activation bypasses C1, C4, and C2, starting directly with C3?
Alternative pathway
Which of the following is responsible for promoting the inflammatory reaction by causing mast cell degranulation?
C3a
Study Notes
Biological Activities of the Complement System
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Cell Lysis: The complement system can cause cell death by disrupting the cell membrane, allowing water and electrolytes to enter the cell, ultimately leading to cell lysis, often seen in bacterial cells, red blood cells, graft cells, or tumor cells.
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Opsonization: Complement component C3b acts as an opsonin, enhancing phagocytosis of cells and antigen-antibody complexes.
Inflammatory Reactions
- Chemotaxis: C5a is a chemotactic agent, attracting neutrophils and macrophages to the site of inflammation.
- Anaphylatoxins: C3a, C4a, and C5a are anaphylatoxins, causing degranulation of mast cells and releasing histamine and other inflammatory mediators, promoting the inflammatory reaction.
Complement System Activation Pathways
- Classical Pathway: All components, starting with C1, are activated in this pathway.
- Alternative Pathway: C1, C4, and C2 are bypassed, and C3 is activated directly in this pathway.
- Lectin Pathway: All components, except C1, are activated in this pathway.
This quiz covers the biological activities of the complement system, including cell lysis and opsonization, and their roles in immune responses.
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