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► Med - Year 1 > Complement System > Flashcards

Complement System Flashcards

1
Q

The major humoral effector mechanism of immune resposne

A

complement system

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2
Q

Which is the only antibody-dependent complement activation pathway?

A

Classical (alternative and lectin are antibody-INdependent)

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3
Q

activation of complement system results in the generation of these 4 major immunobiological activities

A
  1. anaphylatoxins
  2. chemoattractants/chemotaxis
  3. Memembrane attack complex (MAC attack!)
  4. Opsonins
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4
Q

Which pathway is considered a pathogen associate molecular pathway? (PAMP?)

A

Mannose binding lectin pathway, which minds to a terminal mannose

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5
Q

what is the humor effector mechanism initiated by?

A

Soluble molecules (classical requires antibody, connecting it to adaptive immune system)

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6
Q

anaphylaxis

A

acute systemic inflammatory response

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7
Q

these factors induce smooth muscle contraction and degranulation of mast cells and basophils

A

Anaphylatoxins

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8
Q

These factors act on neutrophils and monocytes to direct their migration to the antigenic stimulus

A

Chemoattractants/chemotoxins (C5)

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9
Q

This complex produces holes in the membranes of bacterial pathogens and cells, and is comprised of which molecules?

A

Membrane attack complex. Made up of C5b, C6, C7, C8, C9n

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10
Q

The major opsonin of the complement system

A

C3b (a little on C4b)

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11
Q

All three pathways converge at which step to form what?

A

Converge at C3b to then activate membrane attack complex

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12
Q

Activator of C1q

A

IgM (secretes as pentamer) and IgG

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13
Q

Serine proteases when activated

A

C1r and C1s

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14
Q

3 major plays of Classical pathway

A

C1, C4, C2

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15
Q

How many of the globular heads of C1q must bind to the Fc portions of antibodies on bacteria?

A

2 globular heads out of 6.

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16
Q

C3 convertase of classical pathway

A

C4b2a (C4b + C42a)

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17
Q

the bond C4b makes with surface of bacteria

A

labile thioester bond

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18
Q

C3b has same opsinon function as

A

IgG

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19
Q

C3 convertase of classical pathway (C4b2a) function as an enzyme

A

cleaves C3 to generate C3b (large) and C3a (small)

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20
Q

Alternative pathway is activated by a small amount of

A

C3b (can be generated from lectin or classical pathway)

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21
Q

Mannose binding lectin pathway has overall structural homology to C1q, except that it binds to

A

terminal mannose sugar of bacteria

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22
Q

Two molecules associated with MBL structure and 2 important properties

A

MASP-1, MASP-2

1) antibody independent
2) like C1r and C1s, they are serine proteases

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23
Q

In alternative pathway, C3b bound to bacteria provides a binding site for

A

Factor B

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24
Q

Major players in alternative pathway

A

Factor B and D

25
Q

This factor circulate in its active form and cleaves B into Bb

A

Factor D

26
Q

C3 convertase of alternative pathway

A

C3bBb

27
Q

In addition to binding to bacteria to instigate the alternative pathway, what else can C3b do?

A

Acts as an opsonin and can bind with C3 convertases

28
Q

C5 convertases

A

Classical/MBL: C4b2a3b
Alternative: C3bBb3b
final step in complement cascade

29
Q

C5 convertases activity

A

Cleave C5 into C5a and C5b

30
Q

Binds to antigen surface and begins formation of MAC

A

C5b

31
Q

What is most important deficiency in complement pathway

A

C3

32
Q

Promote the movement of leukocytes from blood into soft tissue and changes blood flow so that increase adhesion molecules are expressed

A

Anaphylatoxins

33
Q

Deficiency of MAC is only a problem when dealing with this one type of bacteria

A

Nysteria

34
Q

Recurrent infections from C3 deficiecny

A

Pyogenic Infection (looks similar to C3b deficiency)

35
Q

Properdin is a stimulatory regulatory molecule found in solution (soluble) that stabilizes which complex?

A

C3bBb (C3 convertase of alternative pathway)

36
Q

C1 inhibitior (C1-INH) stops complement activation at which stage?

A

C1 activation: dissociates C1q from (C1r+C1s)

37
Q

individuals that lack C1-INH develop this serious condition

A

Hereditary Angioneurotic Edema (usually see the accumulation of fluids in the larynx)

38
Q

C4 -binding protein (C4BP) inhibits which stage of complement activation?

A

Classical and Mannose C3 convertase.

Dissociates C4b2a —> (C4b + C2a)

39
Q

Cofactor for Factor I

A

C4BP

40
Q

degrades C4b and C3b using C4BP or H as cofactor by proteolysis

A

Factor I

41
Q

Why does Factor I cleave C4b and C3b?

A

so that those molecules wont re react with C2a and Bb respectively

42
Q

An increase in [C3b] circulating is due to a deficiency in this

A

Factor I (cleaves C3b)

43
Q

Dissociates alternative pathway C3 convertase into C3b and Bb

A

Factor H

44
Q

Two types of regulatory molecules/ inhibitors in complement pathway

A

soluble (found in solution) and membrane associate (found on human cell membranes)

45
Q

3 regulatory membrane bound molecules

A
  1. DAF (decay accelerating factor)
  2. CD59
  3. MCP (membrane co-factor protein)
46
Q

Disease associated with absence of DAF and CD59

A

Paroxysmal Nocturnal Hemoglobinuria = destruction of RBC

47
Q

DAF and CD59 are bound to membrane by

A

GPI linkages

48
Q

DAF and CD59 protect against

A

Membrane attack complex (MAC)

49
Q

Why can’t RBC block MAC formation?

A

Not nucleated (nucleated cells have regulatory protective mechanism and can also repair damage to cell membrane)

50
Q

Receptor for C3b and C4b

A

CR1

51
Q

Interaction of CR1 with its ligands stimulate

A

phagocytosis, erythrocyte transport of immune complexes and promotes C3b and C4b decay

52
Q

how do CR1 on RBCs work?

A

Bind to immune complex in blood and eliminates it through the spleen; RBC returns to circulation

53
Q

Main Fc receptor that promotes phagocytosis

A

Fc gamma R1 (for antibody IgG1)

54
Q

Fc receptor binds to

A

Fc portion of an antibody that is bound to an antigen

55
Q

Fc gammaR1 receptor for which antibody

A

IgG

56
Q

Fc epsilonR1 is receptor for which antibody

A

IgE

57
Q

Fc epsilonR1 is found on what cells

A

mast cells and basophils

58
Q

Fc gammaR1 is found on what cells

A

phagocytic cells (macrophages and neutrophils)

► Med - Year 1 (48 decks)

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