Please enable JavaScript.
Coggle requires JavaScript to display documents.
THE COMPLEMENT SYSTEM, SANDHYA A 191822016 - Coggle Diagram
THE COMPLEMENT SYSTEM
DEFINITION
The complement system, also known as complement cascade, is a part of the immune system that enhances (complements) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promote inflammation, and attack the pathogen's cell membrane
-
EFFECTS OF COMPLEMENT
Lysis of cells (bacteria, allografts, tumor cells)
-
-
PATHWAY
Classical
Is antibody dependent pathway and triggered by formation of soluble antigen-antibody complex or by binding of the antibody to the antigen present on the target cell surface.
Alternative
Is antibody independent pathway stimulated by antigen directly eg. Bacterial cell surface components.
-
-
MEMBRANE ATTECK COMPLEX
-
C5 (structurally homologous to C3 and C4, lacks internal thioester bond )
C5b initiates formation of MAC (complex of C5b, C6, C7, C8 and multiple C9 molecules ) binds to C6, and C7 , recruits C8 and complex penetrates more deeply into the membrane.
C9, a pore-forming molecule with homology to perforin. The complex of C5b678 forms a nidus for C9 binding and polymerization
-
Disrupt the osmotic barrier, leading to swelling and lysis of susceptible cells
BIOLOGICAL EFFECTS
Anaphylatoxin (C3a, C4a, C5a) • Cause degranulation of mast cells • Bind directly to smooth muscles of bronchioles bronchospasm
Chemotaxis • C5a and C5,6,7 complex - attract neutrophils • C5a – enhance adhesiveness of neutrophils to the endothelium
-
-
Enhancement of antibody production • Binding of C3b to its receptors on the surface of activated B cells - enhanced antibody production
-
CLINICAL ASPECTS
-
Deficiency of C3 • Severe, recurrent pyogenic sinus & resp. tract infections
-
-
Transfusion mismatches • Activation of complement generate large amounts of anaphylatoxins & MAC red cell hemolysis
Autoimmune diseases • Immune complexes bind complement low complement levels + activate inflammation tissue damage
Severe liver disease • Deficient complement proteins predispose to infection with pyogenic bacteria
Factor I deficiency • Low levels of C3 in plasma due to unregulated activation of alternative pathway recurrent bacterial infections in children • Mutations in factor I gene implicated in development of Hemolytic Uremic Syndrome
-
-