The complement System Flashcards
What is the definition of inflammation?
The process of vascularized tissues, with fluid and leukocytes accumulation at the site of injury.
Transudation
The movement of fluid with low levels of plasma protein.
Exudation
The movement of leukocytes and high levels of plasma protein.
Fibrinous Exudate
Large amounts of FIBRIN
Purulent Exudate
Large amounts of neutrophils
Suppurative Inflammation
An inflammation with purulent exudate due to liquefactive necrosis.
What are 3 main functions of the complement system?
“OIL”
- Opsonization
- Inflammatory (pro-)
- Lysis (Membrane Attack Complex)
Complement Activation Pathways In Order
- Alternative Pathway
- Lectin Pathway
- Classic Pathway
Alternative Pathway
- Activated when factor B binds to C3b on the microbial surface.
- Its C3bBb (C3 convertase) converts C3 to C3a and C3b.
- Its C3bBb bind to C3b and forms C3bBb3b (C5 convertase).
- Its C3bBb3b converts C5 to C5a and C5b.
- C5b forms MAC along with C6-C9.
Lectin Pathway
- Activated when “mannose binding lectin (MBL)” binds to mannose sugar on microbial surfaces.
- Its C4b2b (C3 convertase) converts C3 to C3a and C3b.
- Its C4b2b bind to C3b and forms C4b2b3b (C5 convertase).
- Its C4b2b3b converts C5 to C5a and C5b.
- C5b forms MAC along with C6-C9.
Classic Pathway
- Activated when Fc portion of an antibody binds with C1q.
- Its C4b2b (C3 convertase) converts C3 to C3a and C3b.
- Its C4b2b bind to C3b and forms C4b2b3b (C5 convertase).
- Its C4b2b3b converts C5 to C5a and C5b.
- C5b forms MAC along with C6-C9.
What complement protein functions as an opsonin?
C3b
What complement proteins function as anaphylatoxins?
C3a, C4a, and C5a
What complement proteins form MAC to lyse the microbe?
C5b and C6-C9
What is the function of DAF?
Decay-Accelerating Factor down-regulates the C3 convertase by displacing Bb from C3bBb.
What happens with DAF deficiency?
The complement activation will be uncontrolled leading to RBC lysis, causing PNH (Paroxysmal Nocturnal Hemoglobinuria).
What is the function of C1-INH?
C1-Inhibitor is a protease inhibitor that down-regulates C1r and C12 activation in the classical pathway.
- C1-INH down-regulates the Bradykinin Pathway.
What happens with C1-INH Deficiency?
C1 activation will be uncontrolled leading to excessive vasoactive peptides being generated, causing Hereditary Angioedema.
What happens with C3 deficiency?
Results in recurrent pyogenic (causing pus) infections and profound risk of encapsulated bacteria infection.
What happens with C5b, C6, C7, C8, and C9 deficiency?
Increased susceptibility to Neisseria Infections.
What happens with C1, C2, C4 deficiency?
Increased risk of immune complex disease, SLE.
What happens with C1-INH deficiency?
Excess of vasoactive peptides (bradykinin generated), causing Hereditary Angioedema.
