Complement System Flashcards
What is the typical order of pathways of the complement system?
Alternative pathway->Lectin Pathway-> Classical pathway
What are the complement proteins that make the cell more proinflammatory and help recruit leukocytes?
C3a, C4a, C5a
Which is the final protein before MAC formation?
C5b
What is the role of C3b?
Opsonization
What is the role of opsonization?
Acts like a glue to attach substances or antibodies to invading organisms to help phagocytosis occur via macrophages/neutrophils
What are the 3 main roles of the complement system?
Opsonization, Inflammation, Lysis
How is the Alternative pathway started?
Spontaneous C3b binding to bacteria within the blood stream
How is the Lectin pathway started?
Binding of mannose binding protein, which occurs normally in circulation, to a mannose residue on a bacterial surface
How is the classical pathway started?
When IgG and IgM bind to antigens on microbial surfaces
What are the anaphylatoxins and what do they do?
C3a, C4a, C5a; They act as vasoactive mediators
What are the chemoattractants?
C3a, C4a, C5a
What are two mechanisms where the complement system is regulated? And how do they act?
Decay-accelerating factor and C1-Inhibitor; DAF down-regulates C3 convertase by displacing Bb subunit on C3bBb while C1-inhibitor down-regulates C1 activation
What is a risk of C3 deficiency?
Profound risk of encapsulated bacterial infection
What is a risk of C5b, C6, C7, C8, C9 deficiency?
Increased susceptibility to Neisseria infections
What is a risk of C1, C2, C4 deficiency?
Associated with increased risk of immune complex disease, SLE
