Complement Flashcards
What is complement?
A system of interacting proteins that play a role in innate immunity and inflammation (p.199)
What types of bacteria does the Membrane attack complex (MAC) of complement specifically protect against?
Gram negative bacteria (p.199)
What immunoglobulins mediate activation of the classic pathway of complement?
IgG or IgM (pneumonic: GM makes classic cars) (p.199)
What activates the alternative pathway of complement?
Microbe surface molecules (p.199)
What activates the lectin pathway of complement activation?
Mannose or other sugars on the microbe surface (p.199)
What are the three pathways of complement activation?
Classic, Alternative, Lectin pathways (p.199)
What is the function of C3b?
Opsonization (p.199)
What is the function of C3a and C5a together?
Anaphylaxis (p.199)
What is the function of C5a individually?
Neutrophil chemotaxis (p.199)
What complement factors are involved in cytolysis by MAC?
C5b- C9 (p.199)
Name the two primary opsonins in bacterial defense.
C3b and IgG (p.199)
Name another important function of C3b.
C3b helps clear immune complexes (p.199)
What two factors inhibit complement activation on self cells (e.x. RBCs)?
Decay accelerating factor (DAF) and C1 esterase inhibitor (p.199)
Describe the steps of the alternative pathway of complement activation.
Spontaneous and microbial surfaces act on C3. C3 –> C3b –> C3 Convertase –> C3a + C3b. C3b –> C5 convertase –> C5b –> MAC –> lysis, cytotoxicity (p.199)
Describe the steps of the classic pathway of complement activation.
Antigen antibody complexes cause C1 to convert C2 –> C2a which when added to C4b becomes C3 convertase –> C3b + C3a. C3b –> C5 convertase –> C5b –> MAC –> lysis, cytotoxicity (p.199)
Describe the steps of the alternative pathway of complement activation.
Microbial surfaces (ex. Mannose) turns a C1 like complex into C1. C1 converts C2 –> C2a which when added to C4b becomes C3 convertase –> C3b + C3a. C3b –> C5 convertase –> C5b –> MAC –> lysis, cytotoxicity (p.199)
What are the clinical manifestations of a C1 esterase inhibitor deficiency?
Hereditary angioedema (p.200)
What types of medications are contraindicated in a patient with a C1 esterase inhibitor deficiency?
ACE inhibitors (p.200)
What are the clinical manifestations of a C3 deficiency?
Severe, recurrent pyogenic sinus and respiratory tract infections; increased susceptability to type III hypersensitivity reactions (p.200)
What are the clinical manifestations of a C5-C9 deficiency?
Recurrent Neisseria bacteremia (p.200)
What type of bacterial infection is most common in patients with a C5-C9 deficiency?
Neisseria bacteremia (p.200)
What are the clinical manifestations of a DAF (GPI anchored enzyme) deficiency?
Complement mediated lysis of RBCs and paroxysmal nocturnal hemoglobinuria (PNH) (p.200)
