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Basic Immunology- Module 1 > B effector functions > Flashcards

B effector functions Flashcards

1
Q

What type of protein are immunoglobulins?

A

soluble glycoproteins

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2
Q

What is an antibody?

A

protein produced in response to an antigen that binds specficially to that antigen

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3
Q

What are the secondary effector functions of antibodies?

A

complement activation; opsonisation; cell activation via Fc receptors

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4
Q

What are the 2 general functions of antibodies?

A

bind specifically to the pathogen or its products that have elicited the immune response; recruit other cells and molecules to destroy the pathogen once the antibody is bound

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5
Q

What are the types of the constant region on antibodies known as?

A

isotypes

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6
Q

What is avidity?

A

total strength of interactions on an antibody- multiple interactions bewteen an antibody with multiple binding sites and a complex antigen with multiple epitopes

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7
Q

What is affinity?

A

strength of the interaction between a single antigen binding site and its antigen

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8
Q

What are the 2 forms of light chain?

A

lambda and kappa

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9
Q

What part of the natibody confers the functional effector properties of the different classes of antibody?

A

the carboxy-terminal part of the heavy chain which isn’t connected to the light chain

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10
Q

What is the difference in structure between the BCR and an antibody?

A

in the BCR the carboxy-terminal is a hydrophobic amino acids to anchor molecule in membrane, whereas the terminus its a hydrophilic sequence to allow secretion

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11
Q

What is the immunoglobulin domain?

A

repeats found in each heavy and light chain of a series of amino acids sequences which correspond to a discrete, compactly folded region of protein

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12
Q

How many Ig domains does a light chain have?

A

2

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13
Q

How many Ig domains does a heavy chain have?

A

4

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14
Q

What is the structure of each V or C domain in an antibody?

A

-immunoglobulin fold: 2 beta sheets built from several beta strands, which are folded onto each otehr to form a beta sandwich

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15
Q

What bonds hold the immunoglobulin fold together?

A

backbone hydrogen bonds between adjacent strands ; covalent link by disulfide bond between cysteine residues on each sheet

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16
Q

What is the main difference in structure between V and C domains on an antibody?

A

V domain is larger and contains extra beta strands

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17
Q

What joins the 2 arms of the immunoglobulin to the trunk?

A

flexible atretch of polypeptide chain- hinge region

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18
Q

What is the effect of papain on an immunoglobulin?

A

cuts the amino-terminal side of the disuflide bond that links the heavy chains together

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19
Q

What is attached to the CH2 domains of the immunoglobulin?

A

carbohydrate

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20
Q

What is the effect of pepsin on the immunoglobulin?

A

cuts the carboxy-terminal side of the disulfide bond linking the heavy chains- leaving a F(ab’)2 fragment and the other heavy chain into small fragments

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21
Q

What is the F(ab’)2 fragment?

A

both antigen binding arms of the antibody are liinked

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22
Q

What is F(ab’)2 fragment written with a prime?

A

it conts a few more amino acids than Fab including the cysteins that form the disulfide bonds

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23
Q

What is significant about the hinge region of immunoglobulins?

A

allows some degree of independent movement of hte 2 Fab arms

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24
Q

What is the hinge region of the Ig also known as?

A

molecular ball and socket joint

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25
Q

Where else is there flexibility of movement in the antibody molecule?

A

between the V and C regions

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26
Q

What is the function of flexibility at the hinge and V-C junction?

A

allows 2 arms of the antibody to bind to sites some distances apart e.g repeating sites of bacterial cell walls

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27
Q

How many polypeptide chains is the IgG antibody made up of?

A

4

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28
Q

What is the purpose of having 2 antigen binding sites on an antibody?

A

antibody molecules can cross-link antigens and bind much more stably and with higher avidity

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29
Q

Is sequence variaiblity distributed evenly thoughout the V regions of the antibody?

A

no- concentrated in certain segments: hypervariable regions

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30
Q

What is the most variable part of hte domain on antibodies?

A

VH3

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31
Q

What are the regions in between the hypervariable regions of the V domains called?

A

framework regions

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32
Q

How many framework regions are there in each V domain?

A

4- FR1, FR2, FR3 and FR4

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33
Q

What forms the beta sheets that create the strcutre of the immunoglobulin domain?

A

framework regions

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34
Q

Where are the hypervariable regions found in the structure of the Ig domain?

A

3 loops near one another in the folded domain at the outer edge of the beta sandwich

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35
Q

What is combinatorial diversity?

A

different combinations of heavy and light chain V regions to create antibody diversity

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36
Q

What is a hapten?

A

small molecules of various types about the size of a tyrosine side chain

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37
Q

What is the structure recognised by an antibody called?

A

antigenic determinent or epitope

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38
Q

What is a discontinous or conformational epitope?

A

structure recognised by antibody is composed of segments of the protein that are discontinous in the amino acid sequnce but are brought together in the antigens 3D structure

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39
Q

What type of forces are involved in the antigen and antibody interaction?

A

reversible noncovalent interactions

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40
Q

Give examples of noncovalent forces in the antibody antigen interaction?

A

electrostatic; hydrogen; van der waals; hydrophobic; cation-pi

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41
Q

What are cation-pi interactions?

A

non-covalent interaction between a cation and an electron cloud of a nearby aromatic group

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42
Q

What is steric hindrance?

A

presence of one Fab blocking the ability of another Fab to bind to some nearby protein sites

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43
Q

What is antibody cross-reactivity?

A

antibody elicited in response to one antigen can also recognise a different antigen

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44
Q

How many subclasses of IgG heavy chain are ther?

A

4

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45
Q

How many subclasses of IgA heavy chain are there?

A

2

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46
Q

what is the functional difference between the lambda and kappa light chains?

A

there doesn’t appear to be one

47
Q

What immunoglobulins do all naive B cells express?

A

IgM and IgD

48
Q

What is the structure of IgM?

A

large pentameric moelcule- 5 monomers joined by J chain (10xFab)

49
Q

Where is IgM mainly found in the body?

A

blood (80%)

50
Q

Why do IgM have multiple binding sites?

A

compensates for low affinity

51
Q

What are the functions of IgM?

A

first Ig synthesised in immune response; efficient at agglutination; activates complement

52
Q

Which antibodies are able to interact with C1 to activate the classical complement pathway?

A

IgM and most IgG subtypes

53
Q

What is the function of IgD?

A

involved in B cell development and activation

54
Q

What is the second most abundant Ig after IgG?

A

IgA

55
Q

What is the structure of IgA in the blood?

A

monomer

56
Q

What is the structure of IgA in secretions?

A

dimer joined by J chain

57
Q

What is the function of IgA?

A

protects mucosal surfaces from bacteria, viruses and protozoa

58
Q

Where are IgA plasma secreting cells found in epithelium?

A

lamina propria

59
Q

What receptor does the dimeric form of IgA bind to?

A

polymeric immunoglobulin receptor (pIgR)

60
Q

Where is pIgR found?

A

basolateral surfaces of epithelial cells

61
Q

What is the name of the process by which IgA is transported in a vesicle thorugh the epithelial cytoplasm?

A

transcytosis

62
Q

What other antibody can bind to pIgR?

A

IgM

63
Q

How is the antibody released from the epithelial cell during transcytosis?

A

by proteolytic cleavage of the rxtracellular domain of the pIgR

64
Q

What is the cleaved extracellular domain of the pIgR that remains attached to the IgA called?

A

secretory component

65
Q

Which part of the IgA does the secretory component bind to?

A

Fc region of the IgA that binds to Fca receptor I

66
Q

What are the functions of secretory component?

A

binds to mucins in mucus- binding IgA to the mucous layer; protects the antibody from cleavage by gut enzymes

67
Q

When is IgE procued?

A

in response to parasitic infections and in allergic disease

68
Q

What natibody is transported across the placenta?

A

IgG

69
Q

Which antibody is the main activator of the classical complement pathway?

A

IgG- IgG1 and IgG3

70
Q

What receptor does IgG bind to on macrophages and neutrophils?

A

FcyR

71
Q

What does binding of FcyR cause?

A

phagocytosis; release of ROS

72
Q

What is the most common type of IgG subclass?

A

IgG1

73
Q

What is required for the activation of C1q?

A

binding to at least 2 Fc portions

74
Q

Which antibody is most efficient at activating complement?

A

IgM- can bind more than 1 C1q

75
Q

What else is CR1 known as?

A

CD35

76
Q

What else is CR2 known as?

A

CD21

77
Q

What else is CR3 known as?

A

CD11b/CD18 ; Mac-1

78
Q

What else is CR4 known as?

A

CD11c/CD18

79
Q

What does CR1 bind?

A

C3b; C4b

80
Q

Which cells express CR1?

A

phagocytes; neutrophils; RBC; B and T cells

81
Q

What is the function of binding to CR1?

A

phagocytosis; transport of immune complexes; microbicidal activity- in conjucntion with FcyR

82
Q

What does CR2 bind?

A

C3dg

83
Q

What is the function of CR2?

A

co-receptor for B cell activation; trapping of antigen; receptor for EBV

84
Q

What cells express CR2?

A

B cells ; follicular DCs

85
Q

Which cells express CR3?

A

phagocytes; neutrophils; NK cells

86
Q

What binds to CR3?

A

bind iC3b; ICAM and other ligands

87
Q

What is the function of binding to CR3?

A

phagocytosis; leukocyte adhesion to endothleium

88
Q

What does CR4 bind?

A

iC3b

89
Q

What is hte function of binding to CR4?

A

phagocytosis

90
Q

What cells express CR4?

A

DCs; phagocytes; NK cells

91
Q

What does CRIg bind?

A

C3b; iC3b

92
Q

What is the function of binding to CRIg?

A

clearance of opsonised microbes

93
Q

Which cells express CRIg?

A

kupfer cells

94
Q

Which Fcy receptor has t he highest affinity for IgG?

A

FcyRI

95
Q

What is the CD of FcyRI?

A

CD64

96
Q

What is FcyRII CD?

A

CD32

97
Q

What is the CD of FcyRIII?

A

CD16

98
Q

What type of IgG can FcyRII and FcyRIII bind?

A

only immune complexes or surface bound IgG not monomeric IgG

99
Q

What is the function of FcRn?

A

transport maternal IgG across the placenta and from the gut of hte newborn into the plasma; protects plasma IgG from catabolism

100
Q

What are the Fc receptors complosed of?

A

an alpha chain with extracellular domain associated with the y chain which transduces the signal (except for FcyRII)

101
Q

What is the CD for FcaRI?

A

CD89

102
Q

What are the consequences of FcR-Ig interactions?

A

opsonisation and phagocytosis; antiobdy-dependent cellular cytotoxicity; release mediators; signalling

103
Q

What is required for phagocytosis with FcR?

A

engagement of Fcy receptor and CR

104
Q

What is the function of stimulating FcyRI?

A

uptake; stimulation; respiratory burst; induction of killing

105
Q

What is the function of stimulating FcyRII-b2?

A

uptake and inhibition of stimulation

106
Q

What is the function of stimulating FcyRII-b1?

A

no uptake; inhibition of stimulation

107
Q

What type of FcyR is expressed on B cells?

A

FcyRII-b

108
Q

What does CD40 signalling in B-T cell interaction promote?

A

B cell activation; isotype switching

109
Q

What co-stimulation moelcules are found on Tfh cells?

A

ICOS; CD40L; cytokines IL-4 and IL-21

110
Q

What is CD40L deficiency known as?

A

hyper-IgM syndrome

111
Q

What transcription factor is highly expressed when plasma cells exit the follcile early in the antibody cell?

A

Blimp1

112
Q

What transcription factor is seen in germinal centre B cells?

A

Bcl16

113
Q

What is the germinal centre response?

A

class switching; somatic hypermutation- high affinity antibodies

114
Q

How does a B cell act as an immunomodulator?

A

via the cytokines released while sensing the environment

Basic Immunology- Module 1 (31 decks)

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