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Immunology > 7 - Complement > Flashcards

7 - Complement Flashcards

1
Q

What are complements and what is their function?

A

proteases that can form complexes | usually inactivated in the circulation

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2
Q

How are complement proteins activated?

A

when they are cleaved

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3
Q

Which immune system (innate or adaptive) are complements mainly part of?

A

innate

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4
Q

What are the 3 functions of complement?

A

lysis | opsonization | inflammation

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5
Q

What is opsonization? What is the purpose?

A

deposit itself on surface membrane = target it for phagocytosis | purpose = for phagocytic cells to recognize the opsonin

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6
Q

What 2 antibodies are the only ones that recognize complements?

A

IgM and IgG

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7
Q

What does the classical pathway recognize?

A

Ag/Ab complexes

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8
Q

What does the lectin pathway recognize?

A

polysaccharides on microbial or antigen surfaces

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9
Q

What does the alternative pathway recognize?

A

C3b (includes those from spontaneously cleaved C3)

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10
Q

What is the initiator of the classical pathway and what does it do?

A

C1 = cleaves C4 and C2 making it into C3 convertase

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11
Q

What is the initiator of the lectin pathway and does it do?

A

MASP = cleaves C4 and C2 making it into C3 convertase

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12
Q

What is the initiator of the alternative tickover pathway?

A

fluid-phase C3 convertase

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13
Q

What is complement deposition?

A

when complement protein deposits itself on membrane surface

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14
Q

What are the 2 functions of C3b?

A

opsonization | gets rid of Ag/Ab complexes = prevents it from accumulating

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15
Q

What is the autoimmune disease that Ag/Ab complexes have a role in when they accumulate and clot in the capillaries and joints?

A

systematic lupus erythematosus (SLE)

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16
Q

What are the 2 anaphylatoxins that causes inflammation?

A

C3a and C5a

17
Q

In the classical and lectin pathways, what is C3 convertase made from? (nomenclature name)

A

C4bC2a

18
Q

In the classical and lectin pathways, what is C5 convertase made from? (nomenclature name)

A

C4bC2aC3b

19
Q

How stable are complement proteins and what does this indicate?

A

not stable = doesn’t last long = will degrade if not active

20
Q

How does lysis occur due to complement proteins?

A

forms MAC complex = forms pore/hole on membrane = lysis

21
Q

What are the complement proteins that form the MAC complex?

A

C5b, C6-9 (6, 7, 8, 9)

22
Q

What is C3 convertase made from/formed in the Tickover alternative pathway?

A

C3bBb (Bb is from Factor B which was cleaved by Factor D)

23
Q

What is properdin?

A

factor that stabilizes C3 convertase in the alternative pathway

24
Q

What is C5 convertase made from/formed in the Tickover alternative pathway?

A

C3bBbC3b

25
Q

What is MBL in the lectin pathway?

A

mannose-binding lectin = part of MASP complex

26
Q

What is the role of thrombin in alternative pathway?

A

can activate the pathway | can cleave both C3 and C5 | activates blood clotting = activates complement

27
Q

What are the 3 complement receptors?

A

CR1, CR2, C3aR/C5aR

28
Q

What cells express CR1 receptors?

A

RBCs, phagocytes, B-cells

29
Q

What does CR1 bind to?

A

C3b

30
Q

What happens when CR1 binds to RBCs?

A

bring immune complexes to the liver for clearance via phagocytosis

31
Q

What happens when CR1 binds to phagocytes?

A

helps bind to complement coated bacteria = ingestion and destruction

32
Q

What happens when CR1 binds to B-cells?

A

induces processing of antigen and present it to T-cells

33
Q

Which cells express CR2?

A

only B-cells

34
Q

What does CR2 recognize/bind to?

A

C3b

35
Q

What happens when CR2 binds to B-cells?

A

helps with B-cell intracellular signaling

36
Q

What cells express the C3aR and C5aR receptors?

A

granulocytes

37
Q

What do C3aR and C5aR recognize respectively?

A

C3a and C5a

38
Q

What happens when either C3aR or C5aR binds to C3a or C5a?

A

release of pro-inflammatory cytokines and granules

Immunology (15 decks)

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