Immunology 3

Question 1

What is clonal selection?

Answer 1

Clonal selection is a process proposed to explain how a single B or T cell that recognizes an antigen that enters the body is selected from the pre-existing cell pool of differing antigen specificities and then reproduced to generate a clonal cell population that eliminates the antigen.

Question 2

What are Plasma cells?

Answer 2

Mature B cells that produce antibodies - each antibody produced is a clone of the receptor

Question 3

What is needed to activate a B cell?

Answer 3

Antibody-antigen interaction
T cell stimulation
Non-T cell stimulation e.f. inflammatory mediators

Question 4

What is the difference between the primary response and the secondary response?

Answer 4

The secondary response is much quicker and larger.
The primary response has a slow rise in IgM followed by a slow rise in IgG.
The secondary repose is characterised by a large increase in IgG - there is a limited rise in IgM.

Question 5

Which cells are antigen presenting?

Answer 5

• Macrophages
• Dendritic cells
• B cells

Question 6

Do antibodies act as T cell or B cell receptors?

Answer 6

B cells

Question 7

Which model is used to describe antibody-antigen interactions?

Answer 7

Lock and Key

Question 8

What is the difference between monoclonal and polyclonal antibodies?

Answer 8

Monoclonal antibodies can only bind to one type of epitope.

Polyclonal antibodies can bind to more than one epitope of a single antigen - this may be on the same pathogen.

Question 9

What is an epitope?

Answer 9

The part of an antigen molecule to which an antibody attaches itself.

Question 10

Which antibody is able to enter tissue space?

Answer 10

IgG

Question 11

Which antibody is found mainly in the bloodstream?

Answer 11

IgM

Question 12

How does the affinity for an antibody change throughout the response?

Answer 12

Early on in the response when IgM is produced, IgM has a low affinity for the antigen.

Later immune response, produced IgG which has a high affinity for the antigen. IgG is found in the blood and intestinal tissue.

Question 13

How can the virus’ introduced in a vaccine?

Answer 13

• Attenuated version of the virus
• Dead virus
• The antigen alone

Question 14

Why are booster injections used?

Answer 14

To ensure immunity remains at adequate levels.

Question 15

What I the reason for repeated allergic reactions?

Answer 15

Elevated levels of IgE.

Question 16

Can monoclonal antibodies recognise only recognise one pathogen?

Answer 16

Not necessarily, the epitope may be found on more than one strain.

Question 17

What is the role of B cells?

Answer 17

1. Activate the complement system through the formation of the antigen-antibody complex.
2. Produce antibodies.
3. Mature into memory cells to produce an immunological memory

Question 18

What are the two antigens in the Hepatitis B?

Answer 18

The Hepatitis surface antigen (HbsAg)
Hepatitis core antigen (HBcAg) - not tested for but antibodies can be detected (HBcAb) indicating current or previous infection

Question 19

In the following scenario, is the individual susceptible to Hepatitis B?

Patient 1:
HBsAg: negative
Anti-HBsAb: negative
Anti-HBcAb: negative

Answer 19

Yes, as they do not have the antibody to protect themselves. They however do not have the active disease.

Question 20

What is the diagnosis for the following patient?
HBsAg: positive
Anti-HBsAb: negative
Anti-HBcAb: positive
Anti-HbcAb (IgM): positive

Answer 20

They have Hepatitis B - it is more likely early on in the infection as the immune system has not had time to develop antibodies.

Question 21

What is the diagnosis for the following patient?
HBsAg: negative
Anti-HBsAb: positive
Anti-HBcAb: positive

Answer 21

They do not have Hepatitis B as the antigen is not detected however they previously had the infection as they have antibodies against the virus as a result there is an immunological memory.

Question 22

What is the diagnosis for the following patient?
HBsAg: negative
Anti-HBsAb: positive
Anti-HBcAb: negative

Answer 22

They were vaccinated against Hepatitis B as the vaccine contains the surface antigen. They were therefore able to produce antibodies against the virus. They however do not have the virus.

Question 23

What is the cause of Graves’ disease?

Answer 23

Antibodies are produced that bind to the TSH receptor - this causes stimulation of thyroid leading to overproduction of T3 and T4.

Question 24

How are autoimmune diseases frequently decocted?

Answer 24

By detecting high levels of a particular antibody