Complement System - Lecture 10

Question 1

Complement System Key Points

Answer 1

-system of plasma proteins MADE BY THE LIVER
-generate INNATE & ADAPTIVE IMMUNE RESPONSES

Question 2

C1

Answer 2

Complex of 3 subunits including C1q, C1r, C1s

Question 3

C3

Answer 3

Central Protein

Question 4

All 3 activation pathways aim to activate

Answer 4

C3

Question 5

Activation occurs in both __ & __ immune responses

Answer 5

Innate & adaptive

Question 6

Opsonization -

Answer 6

C3b

Question 7

Inflammation -

Answer 7

-increase vascular permeability via mast cell & basophil activation - C3a & C5a
-chemotaxis of phagocytes - C5a

Question 8

Cell lysis -

Answer 8

MAC = C5-C9

Question 9

Activation of the classical pathway

Answer 9

C1 complex binds Ag-Ab (immune complex)
-C1 complex = C1q, C1r (2x), C1s (2x)
-C1q binds at least 2 IgG molecules for activation; release vasoactive compounds
[C2 —> C2a + C2b]
[C4 —> C4a + C4b]

Question 10

Amplification of Classical Pathway

Question 11

Alternative Pathway Activation

Answer 11

Microbe binds C3 (no specific region needed - No Ab involved)
-bacteria, fungi, viruses, tumor cells
-spontaneous [C3 —> C3a + C3b]

Question 12

Alternative Pathway Amplification

Answer 12

-C3b binds to Factor B
-Factor D [Factor B —> Factor Ba + Factor Bb]
C3b + Factor Bb = C3bBb = C3 convertase
-[C3 —> C3a + c3B]
C3bBb +C3b = C3bBb3b = C5 convertase
-[C5 —> C5a + C5b]