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Defence > HI > Flashcards

HI Flashcards

1
Q

What are the types of light chain in an antibody?

A

→κ or λ chain

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2
Q

How many types of heavy chains?

A

→5

→μ,δ,γ,α or ε chain

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3
Q

What is the hinge region made from?

A

→disulphide bonds

→between the cystine groups

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4
Q

What Bcells have antibodies?

A

→activate Bcells- membrane bound

→plasma

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5
Q

Which regions make the antigen binding domain?

A

→variable region of H and L

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6
Q

What do all chains have at the beginning and end and why?

A

→NH3 at the beginning
→COO3 at the end

→chains are a string of amino acids

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7
Q

Where is the hinge region and why?

A

→between CH1 and CH2 for flexibility

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8
Q

What group is added to the antibody to allow interaction of immune cells?

A

→CHO glycosylation on CH2

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9
Q

Which fragments make the Fc fragment?

A

→CH2 and CH3 domain

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10
Q

Which fragments make the Fab fragment?

A

→variable and 1st constant domain

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11
Q

What is the function of Fab fragment?

A

→binds to antigens

→antigen-binding site

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12
Q

What is the function of the Fc region?

A

→interacts with Fc receptors on macrophages and some proteins of the complement system

→bear a highly conserved N-glycosylation site

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13
Q

What is the Fv region?

A

→the smallest fragment that maintains the full binding capacity of the intact antibody

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14
Q

What are hypervariable regions?

A

→3 of them

→on heavy and light chains

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15
Q

What are the functions of antibodies?

A 
→Virus & toxin
neutralization- prevents pathogen-host binding
→Opsonization+ ADCP
→Complement fixing/+ 
MAC formation (CDC)-Phagocytosis
or lysis
→Opsonization
\+ ADCC leads to NK-induced apoptosis
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16
Q

What is ADCC and ADCP?

A

→ADCC: an excess of engaged CD16A induces the release of cytotoxic granules which kill the target

→ADCP: an excess of engaged CD32A induces the phagocytosis of the microbe or target cell

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17
Q

What gene region fixes light chain?

A

→VD-J

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18
Q

Describe IgM

A 
→3rd most common 
→heaviest
→fixes complement
→does not cross placenta
→pentameric
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19
Q

What is the function of IgM?

A

→Main Ab of primary response
→ best at forming immune complexes fixing complement;

→monomer serves as BCR

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20
Q

What are the functions of IgD?

A

→BCR;

→indicates mature B cells

→only Ab not secreted

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21
Q

What are the functions of IgG?

A

→Main Ab of secondary responses

→neutralize toxins;

→opsonization

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22
Q

What are the functions of IgA?

A

→Secreted into mucous, tears, saliva, colostrum

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23
Q

What are the functions of IgE?

A

→allergy

→parasite

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24
Q

Which Igs can cross the placenta?

A

→IgG

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25
Q

Which Igs fixes complement?

A

→IgM

→IgG

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26
Q

Which Igs is heaviest?

A

→IgM

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27
Q

How many types of IgG?

A

→1-4

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28
Q

How many types of IgA?

A

→2

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29
Q

Which Igs is involved in primary response?

A

→IgM

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30
Q

What joins the two IgA monomers?

A

→J chain

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31
Q

What is another structure found in IgA?

A

→secretory component

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32
Q

What is the only Ab not secreted?

A

→IgD

33
Q

What are the major changes in heavy chain class switching?

A

→DNA recombination
→IgM to IgG, IgA, IgE
→IgG to IgA, IgE

34
Q

What are the minor heavy chain changes in class switching?

A

→: Differential splicing (mRNA level)

→IgM and IgD

→Does not affect the DNA of Bcell itself

35
Q

What does clas switching recombination require?

A

→Cytokine signal

→Switch regions- infront of constant gene segments constant

→AID and DSB repair proteins

36
Q

What happens to the gene code after class switching occurs?

A

→other regions are removed

37
Q

Before recombination what does the Bcell express?

A

→expresses gene in two forms: IgM and IgD

38
Q

Compare secreted and membrane-bound Abs

A

secreted
→has cytoplasmic tail
→has a tail piece

membrane bound
→hydrophobic transmembrane region
→cytoplasmic tail

39
Q

Which gene regions codes for transmembrane region of membrane bound Ab?

A

→M1 and M2

heavy chain

40
Q

What is unique about transcription of membrane bound Ab?

A

→whole gene region is transcribed

41
Q

What is involved in somatic recombination of Ab?

A

→V(D)J recombination

→Tdt nucleotide addition

→Somatic hypermutation

→Class switching

42
Q

What molecules are involved in class switching recombination?

A

→AID

→DSB repair proteins

43
Q

Which Ab do immature Bcells express?

A

→IgM

44
Q

What are the gene changes that occur between pro-Bcell and mature Bcell?

A

→D to J, heavy chain variable region
→V to DJ
→V to J, light chain variable and constant

45
Q

Where in the antibody does affinity chain maturation occur?

A

→heavy chain constant region

46
Q

What is IgD considered as?

A

→quality control

47
Q

How many Abs genes are inherited?

A

→none

→only gene segments

48
Q

Compare the gene segments of light and heavy chain

A

→heavy chain has D region but light chain doesn’t

49
Q

What do J or D/J region code for?

A

→Codes for CDR3

→Most variable region of Ab

50
Q

What are the genetic loci encoding Ig?

A

→Two for light chain: kappa (κ)- chromosome 2
→lambda (λ) locus- chromosome 22

→One for heavy chain- chromosome 14

51
Q

How many variable region segments does the kappa light have on chromosome 2?

A

→40

52
Q

How many joining segments does kappa light chain have?

A

→5

53
Q

Describe the proximity of V and J and C regions in germline DNA

A

→J segments far from V segment

→J segments closer to C segment than V segment

54
Q

How many variable segments present on gamma heavy chain genes?

A

→51

55
Q

How many D segments on gamma heavy chain?

A

→27

56
Q

How many J segments on gamma heavy chain genes?

A

→6

57
Q

What are RSS?

A

→recombination signal sequences

→conserved sequences upstream or downstream of gene segments

58
Q

What is the function of RSSs?

A

→Turns’ consisting heptamer and nonamer with a 12 or 23 bp spacer

→Recombination only occurs between a segment with a 12bp
spacer and a 23bp spacer

→One turn two turn rule prevents V fragments and V/J fragments from combining

59
Q

What factors are involved in the generation of antibody diversity?

A

→Multiple germline V, D and J gene segments
→Combination V-J and V-D-J joining
→Junctional flexibility
→ P-nucleotide addition
→ N-nucleotide addition
→ Combinatorial association of heavy and light chains
→ Somatic hypermutation during affinity maturation

60
Q

What is a disadvantage of junctional diversity?

A

→incorrect reading frame –

wasteful process eg loss of stop codon

61
Q

What is the difference between minor and major hairpin?

A

→Major hairpin=hole DNA folded in half

→Minor hairpin=between two strands of DNA

62
Q

What is Artemis?

A

→endonuclease

→resolution of hairpin coding ends

63
Q

Describe the junctional diversity process

A

→Once hairpin is formed, the Artemis enzyme nicks on end of the dsDNA

→Nicked ends linearise

→Repair enzymes adds nucleotides P nucleotides

→Tdt adds N nucleotides before the ends are ligated

→P and N nucleotides shifts reading frame

64
Q

Which chain does Tdt mostly work on?

A

→heavy chain

65
Q

How is Ab allele expression different from normal expression?

A

→Two copies of each Ig gene – one from mother and one from father

→ In other cells, both genes are expressed

→Only one heavy chain allele and one light chain allele is expressed

66
Q

State the order of rearrangement in antibody rearrangement

A

→Heavy>kappa>lambda; 1st allele then 2nd

→Ensure each B cell makes one type of antibody

67
Q

Where does class switching occur?

A

→spleen
→lymph node
→light zone

68
Q

What are the two types of Bcell activation?

A

→Tcell independent

→Tcell independent

69
Q

Describe Tcell independent Bcell activation

A

→production of IgM by plasma cells and

→does not produce memory B cells

→clonal expansion

70
Q

Describe Tcell dependent activation

A

→BCR recognise antigen
→Th cell MHC: TCR and CD40 interaction
→cytokines

71
Q

What does SyK do?

A

→phosphorylates signal molecule for Bcell activation

72
Q

Describe affinity maturation

A

→Initially, the antibody binds weakly- low affinity so antigen takes longer to bind to antigen or quickly falls away

→When Bcell is activated, there is mutations in variable region genes and selects for antibodies with best affinity

→occurs in germline centre

73
Q

Which is the only cell that can enter germline centres?

A

→T follicular helper cells (Tfh)

74
Q

Which cells present antigens in the germline centre?

A

→Follicular Dendritic Cells (FDC)

75
Q

Where do activated Bcells go to make clones?

A

→germline centre

76
Q

What changes occur before Bcells turn into plasma or Bcells?

A

→class switching

77
Q

What is the role of AID?

A

→generate point mutation in variable region- somatic hypermutation in dark zones

78
Q

What do Bcells compete for in the light zone?

A

→compete to bind on the FDC and present it to Tfh cells

→Bcells then return to dark zones until affinity is high enough.

→Cells that don’t survive undergo apoptosis

Defence (31 decks)

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