Lecture 3

Question 1

What is the name for the part of the antigen that is recognised by an antibody or immune cell?

Answer 1

The epitope

Question 2

What is the name for the part of the antibody that recognises an antigen?

Answer 2

The paratope

Question 3

What kind of bridges connect the heavy and light chains of an antibody?

Answer 3

Disulphide bridges

Question 4

What are the two different CL (constant light chain domains) available in the genome?

Answer 4

Kappa and lambda

Question 5

How many constant domains does a heavy chain have?

Answer 5

3

Question 6

Name three forces for bonding that are active at the antibody-antigen binding site.

Answer 6

van der Waals
H bonds
Electrical charge

Question 7

What are two characteristics of B cell epitopes?

Answer 7

1. Sequence is always exposed on the surface of the protein/antigen
2. 3D structures are recognised (rather than digested peptide sections).

Question 8

What are two characteristics of T cell epitopes?

Answer 8

1. Recognise antigenic segments in combination with MHC I or MHC II
2. Recognises small peptides of digested antigen (8-12 amino acids) which must fit in the beta-pleasted sheet of the MHC molecule.

Question 9

Which MHC do CD8+ T cells recognise? How big are the epitopes that fit in this molecule?

Answer 9

MHC I - 8-10 amino acids.

Question 10

Which cell types express MHC I?

Answer 10

Most nucleated cells

Question 11

Which MHC do CD4+ T cells recognise? How big are the epitopes presented by this molecule?

Answer 11

MHC II - 13 - 25 amino acids.

Question 12

Which cell types express MHC II?

Answer 12

Antigen presenting cells (e.g macrophages, dendritic cells).

Question 13

What are two fundamental differences in the epitopes recognised by antibodies and T cell receptors?

Answer 13

1. Epitope recognised by T cells can be from ANYWHERE in the antigenic molecule, including the interior structure. Antibodies can only see structures on the exterior of the molecule.
2. T cell epitopes must be linear sequences of amino acids, whilst B cell epitopes are based on 3D conformation - the section recognised may be linear, or may just be nearby

Question 14

What molecules do the lymphocyte subset NK T cells recognise?

Answer 14

CD1d (MHC-like molecule) + glycolipids such as alpha-galactosylceramide.

Question 15

Regarding antibodies, the ___ region of the heavy and light chains determines the paratope.

Answer 15

The variable region of the heavy and light chains determines the paratope.

Question 16

Are antibodies hydrophobic or hydrophilic?

Answer 16

Hydrophilic - they are water soluble.

Question 17

True or false - one individual’s T cells cannot recognise another individual’s MHC I.

Answer 17

True

Question 18

What types of molecules are usually presented on MHC?

Answer 18

Peptides and glycolipids

Question 19

What is the implication of poor refrigeration of B cell vaccines?

Answer 19

Denature the proteins - B cells will not recognise - vaccine no longer effective

Question 20

Why is it more difficult to formulate vaccines for eukaryotic pathogens e.g parasites?

Answer 20

Because they can glycosylate proteins so if your vaccine primes B cells to recognise a parasitic protein, the B cell epitope on the actual parasite may be disguised by glycosylation.