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06. HDM Test 2 > 4. Effector Mechanisms of Humoral Immunity > Flashcards

4. Effector Mechanisms of Humoral Immunity Flashcards

1
Q

What is the function of plasma S protein?

A

Inhibits membrane insertion of C5b-C7, prevents the MAC from beginning.

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2
Q

What sort of bacteria infect patients with C5, 6, 7, 8, and 9 deficiencies?

A

Neisseria bacteria

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3
Q

What two classes of antibodies can activate the classical compliment pathway?

A

IgG

IgM

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4
Q

What is the function of Factor I regarding the complement system?

A

Degrades C3b into iC3b, and C3dg.

Breaks C3b into inactive fragments

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5
Q

What is the function of Decay Accelerating Factor (DAF)?

A

Displaces C2a from C4b and Bb from C3b (dissociates both C3 convertases).

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6
Q

What is the function of CR1 (CD35)?

A

It is a receptor for C3b and C4b, and promotes phagocytosis of C3b- and C4b- coated particles as well as clearance of immune complexes from circulation.

Functions like MCP as a cofactor for C3b cleavage into iC3b

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7
Q

What is the function of FcεRI?

What is the relative affinity for this receptor?

A

Triggers degranulation in eosinophils

High

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8
Q

What class of antibodies is passed via breast milk?

A

IgA

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9
Q

Which Fc receptor “does not mediate effector functions of antibodies?”

What is the affinity for this receptor?

A

FcγRIIb

Low affinity

pg. 174

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10
Q

What is the function of properdin?

A

Stabalizes C3 convertases on microbial surfaces.

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11
Q

What produces C2a and C4b in the lectin pathway?

A

MASPs (MASP 1, 2, and 3)

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12
Q

What three complement deficiencies are associated with Systemic Lupus Erythematosus?

A

C1q, C2, and C4

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13
Q

What is the function of C1 Inhibitor (C1 INH)?

A

Prevents C1r2C1s2 from becoming proteolytically active.

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14
Q

What is the function of FcRn?

A

It is an endosomal receptor in phagocytes and endothelial cells that prevents destruction of IgG, which contributes to its longer half life.

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15
Q

Which two IgG subclasses are the most efficient activators of compliment?

A

IgG3 and IgG1

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16
Q

What is the protective mechanism of antibodies following vaccination against pneumococcal pneumonia / Haemophilus?

A

Opsonization/phagocytosis mediated by IgM and IgG antibodies, and compliment activation.

17
Q

Why might it be beneficial to provide multiple rounds of vaccination?

A

Because affinity maturation will occur after every vaccination, creating more specific antibodies.

18
Q

What sort of infections are associated with C3 deficiencies?

(What sort of bacteria?)

A

Pyogenic bacterial infections

19
Q

What is the most common human complement deficiency?

A

C2 deficiency

20
Q

What Fc receptor is unique to NK cells?

What is its function?

A

FcγRIII

Antibody dependent, cell mediated, cytotoxicity

21
Q

What is steric hindrance?

A

The process by which antibodies bind to structures such as hemagglutinin (influenza virus) and pili (gram negative bacteria) and prevent them from contacting the host cell.

22
Q

What phagocyte receptor recognizes the Fc region of IgG1 and IgG3 and triggers phagocytosis?

What is the relative affinity for this receptor?

A

FcγRI

High affinity

23
Q

What is the function of Factor H?

A

Binds C3b and displaces Bb, dissolving the C3 convertase of the alternative pathway.

Also helps Factor I cleave C3b

24
Q

What is the function of Mebrane Cofactor Protein (MCP)?

A

Helps Factor I cleave C3b and C4b

25
Q

Why might it be advantageous to a prolonged immune response to produce more IgG antibodies?

A

Because IgG antibodies have a half life of about 3 weeks.

26
Q

What is the classical / lectin complement pathway’s C3 convertase?

A

C4bC2a

27
Q

What is bound by C3R and C4R?

What are their functions?

A

iC3b

Phagocytosis and leukocyte adhesion to endothelium via ICAM-1

28
Q

What is the function of CR2 receptors?

A

Bind to inactivated complement products iC3b, C3dg, and C3d and act as a coreceptor for B Cell activation.

Is also a receptor for Epstein-Barr virus to enter B Cells and infect them.

29
Q

Which subtype of IgG is the least efficient opsonin?

A

IgG2

30
Q

Which antibody class is responsible for neonatal immunity by being transferred across the placenta?

A

IgG

31
Q

Why might C2 and C4 deficiencies not be associated with increased rates of infections?

A

Because the alternative pathway can compensate for the lack.

32
Q

Why can’t complement bind to soluble IgM?

A

IgM undergoes a shape change after it binds, allowing C1 to bind to it.

33
Q

What forces attach complement proteins to microbes?

A

Covalent attachment

34
Q

What is the function of CD59?

A

Inhibits Poly-C9 (from the MAC) assembly.

35
Q

Which antibody class is responsible for opsonization?

A

IgG

36
Q

What are the three subunits of the C1 complement protein?

What are their functions?

A

C1q, C1r, C1s

C1q binds to the antibody via its H head

C1r and C1s are proteases

37
Q

Why would the C1 complex not activate the complement cascade when binding to one Fc portion of IgG?

Why is this important?

A

Because it must bind to two or more to activate the complement cascade.

Prevents complement activating from soluble IgG

06. HDM Test 2 (9 decks)

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