Immunology 3

Question 1

Describe the structure of an antibody

Answer 1

Made of 4 polypeptide chains:
- 2 Light chains
- 2 Heavy chains

• 2 disulphide bonds link the heavy chains, two more link the light chain to the heavy
  chain

Question 2

Whats the role of immunoglobulins?

Answer 2

• Recognise and bind to an antigen & elicit effector functions
• Functions are performed by the variable and constant regions

Question 3

What does the word affinity mean?

Answer 3

The strength of binding of one molecule to another at a single site

Question 4

What does the word avidity mean?

Answer 4

The total of the strength of binding of two molecules or cells to each other at multiple sites

Question 5

What are the 5 different classes of Ig determined by?
What are they?

Answer 5

• Determined on the heavy chains
• Gamma = IgG
• Alpha = IgA
• Mu=IgM
• Epsilon = IgE
• Delta = IgD

Question 6

What do heavy and light chains consist of?

Answer 6

Repeated similar domains known as the immunoglobulin fold - provides antigenic variability

Question 7

How many folds does the light chain and heavy chain have in IgG?

Answer 7

Light chain - 2 folds
Heavy chain - 4 folds

Question 8

What is combinatorial diversity?

Answer 8

Different specificities created by different combinations of heavy and light chains

Question 9

What can the non-covalent interactions between antigen and antibodies be disrupted by?

Answer 9

• High salt concentrations
• Extremes of pH
• Detergents
• High concentrations of purified epitope

Question 10

Describe the determination of function of different immunoglobulins

Answer 10

1. Neutralisation:
   - Antibodies bind to pathogen
   and toxins & prevent binding to the cellular receptor’s pathogens used to gain entry to cells.
2. Opsonisation:
   - Coating of the pathogen with
   the antibody
   - Phagocytes recognise the Fc
   region of the antibodies from
   FcRs triggering phagocytosis
3. Activation of the complement pathway to act as opsonin or lysis

Question 11

What happens when antibodies neutralise toxins and microbes?

Answer 11

• Blocks cell and microbial interactions
• Inhibits spread
• Blocks pathological effects of toxins
• Intracellular function for antibody

Question 12

Where does recognition of more rapidly evolving antigens occur?

Answer 12

• In central lymphoid organs such as the thymus and bone marrow
• In peripheral organs such as the appendix, lymph nodes and tonsils

Question 13

What is a gene segment?

Answer 13

The variable regions of Ig genes are encoded in multiple pieces

Question 14

What is germline diversity?

Answer 14

Multiple choices for each gene segment

Question 15

What types of segments are light chain variable regions encoded by?

Answer 15

• V = Variable
• J = Joining

Question 16

What are variable regions brought together by?

Answer 16

One somatic recombination event in light chains

Question 17

What are the different types of heavy chain variable region segments?

Answer 17

• V = Variable
• J = Joining
• D = Diversity

Question 18

What does complete functional rearrangement require?

Answer 18

• One of each type of segment joined in the correct order and orientation
• Controlled by non-encoding, conserved DNA sequences

Question 19

Describe junctional diversity

Answer 19

• Gene segments must be joined together
• RAG proteins cleave the DNA
• Nucleotides are added or subtracted to make a viable joint by TdT
• Position of the cut adds P nucleotides to the sequence, whilst the TDT adds N nucleotides