L15 & L16

Question 1

What is allelic exclusion?

Answer 1

When segments of a gene on one chromosome start to rearrange in BCR development, rearrangements for the gene on the other chromosome are prevented.

Question 2

Which enzyme does VDJ recombination?

Answer 2

RAG

Question 3

What happens if you lack RAG?

Answer 3

SCID

Question 4

T cell independent ab response involves…

Answer 4

no T helper cell, you get IgM, some IgG, a low affinity ab.

Question 5

T cell dependent ab response you get…

Answer 5

Helper T cell, IgM, IgA, IgG, IgE. High affinity ab, memory and long lived.

Question 6

Which B cells have IgM and IgD?

Answer 6

Naive B cells in serum. IgD is a transmembrane receptor on mature B cells.

Question 7

What is the difference between mature and immature B cells?

Answer 7

Immature: IgM
Mature: IgM and IgD
Both naive

Question 8

What B cells have IgG?

Answer 8

Memory B cells in serum

Question 9

What is IgE involved with? Where is it bound?

Answer 9

Mast cells, which it is bound to the surface of.

Question 10

Where is IgA found?

Answer 10

Mucosa and serum

Question 11

Which Ig can transfer through the placenta?

Answer 11

IgG

Question 12

Which Ig is found in classical pathway complement activation?

Answer 12

IgG and IgM

Question 13

Which Ig has high affinity binding to mast cells and basophils?

Answer 13

IgE

Question 14

In what configurations do IgA and IgM exist in?

Answer 14

IgA in dimers and IgM in pentamers when released, linked by a J chain. When surface bound IgM is monomeric.

Question 15

What the difference between avidity and affinity in ab binding?

Answer 15

Affinity is strength of binding of a single Fab to its antigen

Avidity is overall strength of ab:antigen context in which affinity is a part of it and so is structural arrangement e.g. IgM has high avidity as a pentamer

Question 16

What configuration does IgA exist as? What else you know about it?

Answer 16

Mainly a monomer in the blood but dimerisation is needed for secretion. It’s transported through epithelial cells, secreted on gut surface it can bind and neutralise pathogens and toxins. It is able to find and neutralise antigens internalised in endosomes.IgA can export toxins and pathogens from lamina propria while being secreted.

Question 17

What’s the relationship between epitope and antigen?

Answer 17

1 antigen can contain many epitopes. Ab bind to epitopes. So an antigen can be bound by multiple abs.

Question 18

What can abs recognise from epitopes?

Answer 18

Their shape e.g. linear bs conformational epitopes.

Question 19

What chemical forces are used by abs to bind to antigen?

Answer 19

Non-covalent

Question 20

How do the arms of ab work?

Answer 20

They are flexible so can bend at many different angles to bind to antigen

Question 21

What are the 6 main ways abs can work?

Answer 21

1) bind to bacterial toxins and neutralise them so they can’t enter cells.They then get ingested by macrophages
2) Bacteria in extracellular space are opsonised and then ingested by macrophages
3) Bacteria in plasma are opsonised which helps activate complement to get lysis and ingestion
4) ADCC
5) precipitation ( immune complex formation)
6) direct cell activation by Fc receptors on phagocytes

Question 22

What allows crosslinking of Fc receptors?

Answer 22

Free Ig doesn’t cross link Fc receptors (which would be say on a macrophage). Aggregation of Ig on bacterial surface allows crosslinking of Fc receptors leading to activation of macrophage leading to phagocytosis and destruction of the bacterium

Question 23

What is an Fc receptor?

Answer 23

It recognises Ab constant region and these receptors are found on innate immune cells like macrophages.

Question 24

What stand alone mechanism ADCC do abs have?

Answer 24

ab dependent cellular cytotoxicity - ab bind to antigens of pathogen on host cell surface and enable immune cells like NK celsl to target and kill the infected cell

Question 25

How many light chain types can a BCR express?

Answer 25

Only one type either 2 kappa or 2 lamda.

Question 26

What gene determines differences in constant region and thus effector function of ab?

Answer 26

Heavy chain constant region

Question 27

What regions do Fcγ receptors bind to of what ab?

Answer 27

IgG Fc region

Question 28

What are the 2 main uses of abs in therapeutics?

Answer 28

Ig replacement in people with ab deficiency usually polyclonal

Mabs as a class of drug