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Immunology > 5. General effector functions of antibodies > Flashcards

5. General effector functions of antibodies Flashcards

1
Q

which part of the immune system is humoral part of; acquired or innate?

A

acquired

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2
Q

In a primary response to pathogen - what cell is activated and what does it do?

A

B cell

proliferates + differentiates into plasma cells which secrete antibodies

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3
Q

which Ab are secreted in the primary response?

A

IgM

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4
Q

what can IgM class switch into in the primary response?

A

IgG

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5
Q

where are long lived plasma cells stored?

A

bone marrow

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6
Q

which Ab are produced in the secondary response?

A

IgG, IgE, IgA

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7
Q

which has a higher Ab affinity; primary or secondary response?

A

Secondary

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8
Q

Describe the B cell receptor complex

A
  1. Ig in membrane
  2. Heterodimer; Ig-alpha + Ig-beta
  3. Immunoreceptor Tyrosine-based Activation Motifs tails (ITAM tails)
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9
Q

what is the function of the B cell receptor complex

A

Attaches pathogen to stimulate B cell activation

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10
Q

what reaction takes place in the B cell for activation?

A

tyrosine phosphorylation

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11
Q

name 2 other ways B cells are activated - other than the epitope of the pathogen?

A
  1. cd3 attaching to CR2 receptor

2. PAMPs attaching to TLR

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12
Q

what causes B cell differentiation?

A

cytokines

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13
Q

4 different cells B cell differentiates into and their roles

A
  1. Plasma cell = secrete Ab IgM
  2. IgG-expressing cell = secrete IgG
  3. high affinity IgG expressing cell = secrete high affinity IgG
  4. memory B cell
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14
Q

what is a T helper cell?

A

Thymus helper cell

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15
Q

which B cells are involved in T-dependent antibody response?

A

Follicular B cell

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16
Q

which B cells are involved in T-independent antibody response?

A

b1 cells, marginal zone B cells

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17
Q

what attaches to IgM antibodies on B cell in the T-dependent response?

A

protein antigens

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18
Q

what attaches to IgM antibodies on B cell in the T-independent response?

A

non-protein antigens (polysaccharides, glycolipids, nucleic acids)

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19
Q

the helper t cell activates the B cell in the T-dependent response. What activates the B cell in the T-independent response?

A

microbe (epitope, PAMPs) and complement

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20
Q

what Ab does isotype switching produce in T-dependent?

A

high affinity - IgG,E,A

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21
Q

is there class switching in T-independent response? if s which Ab are involved?

A

a little bit - IgM to IgG - but low affinity

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22
Q

2 cells produced in T-dependnent response?

A

memory b cell and long lived plasma cells

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23
Q

what 3 things cause Ab isotype switching

A
  1. cytokines
  2. receptors expressed by B cells
  3. CD40 ligand
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24
Q

what stimulates IgG production (isotype switching)?

A

Various Interleukin

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25
Q

what stimulates IgE production (isotype switching)?

A

IL-4

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26
Q

what stimulates IgA production (isotype switching)?

A

cytokines which are produced in mucosal tissue - such as transforming growth factor Beta TGF-b and B-cell activating factor BAFF)

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27
Q

principal effector function of IgM

A

complement

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28
Q

principal effector function of IgG (3)

A
  1. Fc-receptor dependent phagocytosis
  2. complement
  3. Neonatal immunity
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29
Q

principal effector function of IgE (2)

A
  1. immunity against helminths

2. mast cell degranulation (immediate hypersensitivity)

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30
Q

principal effector function of IgA

A

mucosal immunity

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31
Q

Difference in y-globulin in normal pt and immunised pt

A

immunised will have higher y-globulin level in blood

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32
Q

why is inactivation of B cell needed?

A
  • pathogen killed
  • save energy
  • prevent autoimmune disease
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33
Q

in b cell inactivation, what receptor does the Secreted Ab attach to?

A

Fc receptor

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34
Q

when the Ab attaches to the Fc receptor what occurs to inactivate the B cell?

A

ITIM inactivates ITAM - stops signal

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35
Q

name 6 Ab effector functions - state which 3 are caused by compliment

A
  1. Neutralisation
  2. opsonisation + phagocytosis
  3. ADCC (antibody-dependent cellular cytotoxicity)
    complement
  4. cell lysis
  5. inflammation
  6. phagocytosis of opsonised microbes with C3b
36
Q

which fragment of an Ab has the ag binding site?

A

fab fragment

37
Q

which part of the Ab is involved in isotype switching and why?

A

fc region - has variation in AA sequence

38
Q

Give an example of a type of antibody assay which uses Ab as reagents to bind to the Fc region?

A

ELISA - enzyme linked immunosorbent assay

39
Q

4 ways in which Ab act as adaptor molecules?

A
  1. activate complement
  2. activate other cells
  3. attach to pathogens to allow phagocytosis via recognition killing
  4. activate the cell
40
Q

what are Ab secreted into?

A

blood - systemic circulation

41
Q

which Ab effector function is not isotype and Fc dependent?

A

Neutralisation

42
Q

3 ways in which neutralisation stops infection

A

when Ab attaches to pathogen:

  1. pathogen cannot pass through epithelia - too large
  2. pathogens cannot bind to body cells
  3. block exotoxin
43
Q

explain opsonisation and phagocytosis in steps

A
  1. Ab attaches to Fc receptor on cell
  2. Epitope attaches to binding site on Ab
  3. Fc receptor sends signals into the cell
  4. stimulates phagocytosis
  5. Cell killed - ROS, NO, proteolytic enzymes
44
Q

why is agglutination helpful? which Ab is most useful for this and why?

A

limits activity of pathogen, IgM - lots of Ag binding sites

45
Q

which Ab involved in opsonisation and phagocytosis?

46
Q

describe ADCC

A
  1. IgG attaches to epitope
  2. IgG fc region attaches to Cd16 Fc receptor on Natural killer cells
  3. NK cells secrete perforin to kill cell
47
Q

How and why can Ab be used to treat cancer by the means of ADCC?

A

Ab attach to tumour cells - NK kill.

Tumour cells express more receptors or may have a mutation which will allow Ab to attach.

48
Q

where are complement proteins produced?

49
Q

3 types of complement proteins

A
  1. 3 x C1 + C2-C9
  2. Factor B+D
  3. regulatory proteins
50
Q

what are the 3 different complement pathways

A

classical, lectin, alternative

51
Q

what is the classical comp pathway activated by?

A

IgM/IgG attaching to Ag

52
Q

what is the lectin comp pathway activated by?

A

MBP attaching to mannose residues on microbial cell surface

53
Q

what is the altenative comp pathway activated by?

A

microbial cell surface

54
Q

Describe the steps in which C4 is activated in the classical complement pathway

A
  1. Ag attaches to IgG/IgM
  2. conformational change in Fc region
  3. Fc region binds to C1q
  4. C1r activation
  5. C1s activation
  6. C1s activates C4
55
Q

Describe the steps in which C4 is activated in the lectin complement pathway

A
  1. serum MBP binds to MBP associated protease (MASP)

2. MBP:MASP complex activates C4

56
Q

Classical : what attaches on top of C4b ?

57
Q

what cleaves C2 ?

i) classical
ii) lectin

A

i) C1s

ii) MBP:MASP complex

58
Q

what does C3 convertase consist of in…

i) classical
ii) lectin
iii) alternative

A

i) C4b:C2b
ii) C4b:C2b
iii) Bb:C3b

59
Q

what does C5 convertase consist of in…

i) classical + lectin
ii) alternative

A

i) C4b:C2b:C3b

ii) C3b: Bb:C3b

60
Q

in all complement pathways, what binds to C6?

61
Q

which complement pathway is part of the innate system

A

alternative

62
Q

Alternative comp: why is c3b not broken down?

A

it attaches to Factor B

63
Q

Alternative comp: how is factor B cleaved?

64
Q

Alternative comp: which complex binds to the pathogen membrane?

A

C5 convertase or C3b:Bb:C3b

65
Q

describe steps in formation of MAC

A
  1. C5b, C6, C7 attach to membrabe (via C7)
  2. C8 attaches
  3. C9 attaches
  4. All 1-16 molecules of C9 bind to membrane to form a pore
66
Q

Other function of C3b

A

acts as opsonin to attach to receptors on neutrophils, macrophages and monocytes to stimulate phagocytosis

67
Q

What complement proteins cause inflammation of mast cells and capillary endothelial cells?

A

C3a, C4a, C5a

68
Q

function of C5a

A

chemoattractant of neutophils, monocytes, eosinophils

69
Q

what 2 things regulate complement?

A
  1. unstable active proteins

2. regulatory proteins

70
Q

which Ig is involed in mast cell degranulation?

71
Q

Briefly describe steps in mast cell degranulation

A
  1. IgE attaches to helminths
  2. IgE Fc region attaches to Fc receptor on eosinophils
  3. TH2 cells release IL-5
  4. IL-5 stimulates degranulation process- release of toxins (histamine, heparin)
  5. parasites are killed
72
Q

which specific site is IgA produced?

A

plasma cells in lamina propria of GI and resp tracts

73
Q

explain neonatal immunity in

a) foetus
b) baby

A

a) IgG transported across placenta

b) IgA transported in colostrum/milk through gut

74
Q

3 mechanisms of immune evasion

A
  1. antigenic variation
  2. inhibition of complement
  3. coating of hyaluorinc acid
75
Q

which type of B cells recognise antigens but dont secrete Ab?

A

Naive B lymphocytes

76
Q

which 2 Ab are inserted on naive B cells?

A

IgM and IgD

77
Q

what do B1 cells respond to?

A

non-protein Ag in mucosal tissue and peritoneum

78
Q

what do marginal zone B cells respond to?

A

polysaccharides and lipid antigens

79
Q

function of IgM antibodies (2)

A
  1. clear apoptotic cells

2. protect against bacterial infection

80
Q

where are memory B cells stored?

A

blood, mucosal tissues

81
Q

which Ig is involved in B cell inactivation?

82
Q

what allows the transportation of IgG through the placenta?

83
Q

name 2 regulatory proteins of complement

A
  1. plasma - C1 inhibitor

2. Decay accelerating factor (DAF)

84
Q

function of c1

A

inhibits C1r and C1s serine protease activity

85
Q

function of DAF

A

Inhibits c3 convertase formation

Immunology (11 decks)

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