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Infection, immunity and repair > Antibodies > Flashcards

Antibodies Flashcards

1
Q

What are the receptors that recognise pathogens?

A

PRRs - pathogen recognition receptors
MHC
TCR
BCR

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2
Q

What do PRRs recognise?

A

PAMP - pathogen associated molecular patterns

DAMP - damage associated molecular patterns

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3
Q

How many genes encode for PRRs?

A

100+

Not very polymorphic since there is little variation in PAMPs and DAMPs between individuals

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4
Q

What do MHC recognise?

A

Peptides on classical alpha beta T cells

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5
Q

How many genes encode for MHC?

A

12

Inherit 3 MHC I and 3 MHC II genes from mother and father respectively

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6
Q

What do TCRs recognise?

A

Peptides linked to MHC

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7
Q

How many genes encode for TCRs?

A

Millions

Very polymorphic

Same with BCRs

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8
Q

What do BCRs recognise?

A

Antigens

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9
Q

How many genes encode for BCRs?

A

Millions

Very polymorphic

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10
Q

Where are PRRs found?

A

On surface, intracellularly and secreted

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11
Q

What brings about polymorphism in MHC?

A

Each protein is encoded for individually, so there is increased polymorphism

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12
Q

How does the large genetic variation in TCRs and BCRs arise?

A

Genetic recombination

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13
Q

Describe an antibody molecule

A

Tetramer

Consists of two heavy chains bound together via disulphide bonds

Consists of two light chains bound to the heavy chains via disulphide bonds

Can be split into variable and constant region

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14
Q

Where is the constant region?

A

The constant region is the larger part of the antibody molecule

Determined mostly by the genetic sequence of heavy chain

The light chain can also have variability in the constant chain however, and classify into Kappa and Lambda

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15
Q

How heavy are the heavy chains?

A

50 kD

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16
Q

How heavy are the light chains?

A

25 kD

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17
Q

What is the role of the constant region?

A

Determines the class of antibody

IgM, IgG, IgA, IgD

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18
Q

What is the role of the variable region?

A

Binds to specific epitopes on antigens

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19
Q

What is the hypervariable region?

A

Area on the variable region that has increased variability. Binds to the epitopes of antigens

Also known as conplementarity determining regions

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20
Q

What is another name for the hypervariable region?

A

Complementarity determining region

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21
Q

How does variability arise?

A

Via genetic recombination

22
Q

What are the 3 gene segments on antibodies that give rise to variability?

A

V, D and J segments

23
Q

How many genes form the J, V and D segments in the heavy chain?

A 
V= 40 
D= 27 
J= 6
24
Q

What does J, V and D stand for?

A

Variable, diversity and joining

25
Q

How many genes form J and V regions of the Kappa light chain?

A 
V = 40 
J= 5
26
Q

How does an antibody look like in terms of the V, D and J regions? `

A

Constant region - J - D - V

27
Q

What controls genetic recombination?

A

A series of enzymes encoded by RAG-1 and RAG-2

28
Q

What does RAG stand for?

A

Recombination-activating genes

29
Q

How do RAGs recognise where to recombine?

A

Via recombination signalling sequences

RSSs

30
Q

What are RSSs?

A

Recombination signalling sequences

Sequences of nucelotides found at the end of V, D and J sequences that signal the RAGs to start recombination

31
Q

What is an example of an enzyme encoded by RAG?

A

Recombinase enzyme is involved with V, D, J recombination

32
Q

Additional mechanisms that increase variability of antibody molecules?

A 
Recombinational inaccuracies 
DIfferent splicing in D J regions 
Make soluble or transmembrane form 
Class switching 
Additional nucleotides added via N-region diversity
33
Q

What processes happen in antibody diversification but not TCR diversification?

A

Class switching
Only make transmembrane version
Somatic hypermutation

34
Q

What two types of recombination events happen in the maturation of antibodies?

A

VDG recombination

Class switching

35
Q

What is class switching?

A

Process by which antibody switches its class whilst remaining equally antigen-specific

36
Q

What determines the class of an antibody?

A

Its constant region

37
Q

How do antibodies switch class?

A

With the help of T helper cells

Switch depending on the type of antibody required to combat the pathogen

38
Q

How is class switching different from VDJ recombination?

A

Uses different enzymes

Uses class switching signals instead of recombination signal sequences

39
Q

What classes do the antibodies switch to?

A

From IgM and IgD

To IgA, IgG and IgE

40
Q

What is the consequence of recombination?

A

From less than 200 genes (V (40) D (27) and J (6)) we can make millions of possible combinations

In the heavy chain, the possibility of different variations is 40276 = 6480

Since some antibodies can have the exact same heavy region but different light chain Kappa regions, the variabiliy increases

Possibility of different variations in Kappa light chain is 40*5 = 200

Therefore the possibility of different variations is 200*6480 = over 1 million

Increases if add possibility of Delta light chain combinations

41
Q

What are the properties of IgG?

A

Only antigen that can pass through the placenta

phagocytosis and complement activation

42
Q

What are the functions of IgM?

A

Together with IgD, make up BCR of naive B cells

One of the first antibodies found in the site of infection

Complement activation and agglutination

43
Q

WHat two antibodies make up the BCR of naive B cells?

A

IgM and IgD

44
Q

What is the function of IgE?

A

Triggers inflammatory mediators from mast cells/ basophils

45
Q

What two antibodies form polymers?

A

IgM and IgA

46
Q

How is IgA found in the circulation?

A

When IgA dimerises

Is bound to secretory components that transport secretory IgA to mucosal surfaces

Link together in the ring via J-chains

47
Q

How do the IgA antibodies link together?

A

Via J-chains

48
Q

How is IgM found in the circulation?

A

As a monomer

49
Q

What shape does a IgM polymer make when it dimerises?

A

A pentameric ring

50
Q

How big is the pentameric ring of IgM polymers?

A

1 million Da

Can’t escape circulation in polymeric form

51
Q

Where does genetic recombination of antigen happen?

A

In the variable region

Infection, immunity and repair (52 decks)

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