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Immunology > Lecture 6 - Antibody Effector Function > Flashcards

Lecture 6 - Antibody Effector Function Flashcards

1
Q

Direct and indirect antibody effector functions

A

Direct - Function of Fab, neutralisation

Indirect - Involves Fc, targets bound antigen for phagocytosis, etc

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2
Q

Example of antibody direct mechanism

A

Antibody binds to influenza haemagglutinin

Influenza is now unable to enter host cell

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3
Q

Example of antibody indirect mechanism

A

Antibody binds to target antigen

If IgE, stimulates mast cell degranulation

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4
Q

Opsonisation
1)
2)
3)

A

1) Antibody binds to taret antigen
2) Bind to phagocyte by FcR
3) Phagocytosis

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5
Q

What does ADCC stand for?

A

Antibody-dependent cell-mediated cytotoxicity

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6
Q

Which receptor on a natural killer cell binds to antibody opsonising antigen?

A

FcgRIII (CD16)

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7
Q

Another name for FcgRIII

A

CD16

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8
Q

What is CD16?

A

IgG receptor on the surface of NK cells

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9
Q

What triggers NK cell killing?

A

Crosslinking of CD16/FcgRIII receptors

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10
Q

Mast cell degranulation
1)
2)
3)

A

1) Mast cell is ‘sensitised’ - IgE coats mast cell, binds to FceR
2) IgE Fab region comes into contact with allergen
3) Crosslinking of FceR leads to degranulation

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11
Q

Does a mast cell have a monoclonal or polyclonal antibody coating?

A

Polyclonal.
Can respond to several different allergens
Probably clumps o fmonoclonal antibodies in different places to allow crosslinking, clumping of antibodies

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12
Q

FcgRI affinity

A

High

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13
Q

FcgRIIA affinity

A

Low

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14
Q

FcgRIIB affinity

A

Low

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15
Q

FcgRIIIA affinity

A

Low

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16
Q

FcgRIIIB affinity

A

Low

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17
Q

FcgRI cell distribution

A

Macrophages, neutrophils

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18
Q

FcgRIIA cell distribution

A

Macrophages, neutrophils

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19
Q

FcgRI function

A

Cell activation, phagocytosis

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20
Q

FcgRIIA function

A

Cell activation, phagocytosis

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21
Q

FcgRIIB cell distribution

A

B cells

22
Q

FcgRIIB function

A

B cell inhibition

23
Q

FcgRIIIA cell distribution

A

NK cells

24
Q

FcgRIIIA function

A

NK cell antibody-dependent cell-mediated cytotoxicity

25
Q

FcgRIIIB cell distribution

A

Neutrophils

26
Q

FcgRIIIB function

A

Neutrophil phagocytosis

27
Q

FceRI cell distribution

A

Mast cells

28
Q

FceRI function

A

Mast cell degranulation

29
Q

FceRI affinity

A

High

30
Q

Why are many Fcg receptors low affinity?

A

To keep serum IgG levels high.

If they were high affinity, IgG would be sequestered on cells, like IgE is.

31
Q

High avidity antibodies

A

Multimeric IgM, IgA

32
Q

Which FcgR can stably bind monomeric IgG

A

FcgRI (high affinity).

Can bind a single IgG bound to an antigen

33
Q

Which FcgR need multiple antibodies bound to a pathogen in order for stable binding?

A

FcgRIIA, fcgRIIB, FcgRIIIA, FcgRIIIB

34
Q

What kind of cells do NK cells kill?

A

Virus-infected cells

Not really extracellular bacteria

35
Q

What is the secretory component?

A

Part of the polymeric-Ig receptor on secretory IgA

36
Q

Is IgA dimeric in the blood?

A

Yes

37
Q

How is the classical complement cascade initiated?

A

C1q component of C1 binds to exposed region of IgM or IgG bound to antigen

38
Q

What is C1q?

A

Part of the C1 complex.

C1 is made up of three components, one of which is C1q

39
Q

Which antibody is best at activating complement?

A

IgM.
IgG1, 2 and 3 are capable of activating complement, but need several antibodies bound to antigen to activate it, whereas pentameric IgM only needs one

40
Q

Can free antibodies activate complement?

A

No. Only IgG and IgM complexes can activate complement

41
Q

Which antibodies neutralise?

A

IgG, IgA

42
Q

Which antibodies opsonise?

A

IgG1 > IgG3 > IgG4, IgA

43
Q

Which antibodies induce antibody-dependend cell-mediated cytotoxicity?

A

IgG1, IgG3

44
Q

Which antibodies activate the complement cascade?

A

IgM&raquo_space; IgG1, IgG3 > IgG2, IgA

45
Q

Which antibody degranulates mast cells?

A

IgE

46
Q

Antibody variability types
1)
2)
3)

A

1) Isotype
2) Allotype
3) Idiotype

47
Q

What is allotype?

A

Differences in antibody gene genetic code.
Heritable
Results in different Ig alleles
Doesn’t encode any noticeable difference in function

48
Q

What is idiotype?

A

Diversity in antibody binding sites

~10^7 different binding sites in each individual

49
Q

An equation to quantify proteinomic variability

A

Number of different amino acids at a given position/Frequency of most common amino acid at a given position

50
Q

What are complement proteins very good at killing?

A

Extracellular bacteria

51
Q

What is the most variable region of an antibody?

A

CDR3

Immunology (30 decks)

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