Antibodies

Question 1

What are antibodies?

Answer 1

Antibodies are proteins with specific binding sites, synthesised by B cells.

Question 2

When are antibodies produced?

Answer 2

When the body is infected by non-self material, a B cell produces a specific antibody complimentary to the antigen presented on the surface of the B cell.

Question 3

Why is it possible to have such a variety of antibodies?

Answer 3

They are made of proteins, molecules that occur in an almost infinite number.

Question 4

What do antibodies and antigens form when they have binded?

Answer 4

Antigen-antibody complex.

Question 5

Why is the binding site on an antibody known as a ‘variable region’?

Answer 5

The binding site is different on every antibody as it consists of an amino acid sequence.

Question 6

What is the rest of the antibody known as?

Answer 6

The constant region which binds to receptors on cells such as B cells.

Question 7

What are antibodies made up of?

Answer 7

4 polypeptide chains. The longer pair of chains are known as heavy chains, and the other pair are shorter, known as the light chains.

Question 8

How does the antibody lead to the destruction of an antigen?

Answer 8

They prepare the antigen for destruction. If the antigen is a bacterial cell antibodies:

• cause agglutination of bacterial cells, making it easier for phagocytes to locate them.
• Serve as markers that stimulate phagocytes to engulf the bacterial cells to which they are attached.

Question 9

What is the significance of monoclonal antibodies?

Answer 9

Foreign material is likely to have many hundreds of different antigens on its surface, each inducing a different B cell to multiply and clone itself. Each of these clones will produce a different antibody, which are known as monoclonal antibodies.

Question 10

How can monoclonal antibodies be used to treat cancer?

Answer 10

• Monoclonal antibodies specific to antigens of cancer cells are produced.
• These antibodies are given to a patient and they attach to the receptors on cancer cells.
• They attach to surface of cancer cells and block the chemical signals that stimulate their uncontrolled growth.

Question 11

What can the monoclonal antibody, Herceptin, be used to treat?

Answer 11

Breast cancer. They are not toxic and are highly specific so lead to fewer side affects.

Question 12

What is indirect monoclonal antibody therapy?

Answer 12

Involves attaching a radioactive or cytotoxic drug to the monoclonal antibody. When the antibody attaches to cancer cells, it kills them.

Question 13

What are the advantages of using monoclonal antibodies in the treatment of cancer?

Answer 13

They can be used in smaller doses as they are targeted on specific sites. This makes it cheaper and reduces side affects the drug might have.

Question 14

How can monoclonal antibodies be used in diagnosing disease?

Answer 14

Use a monoclonal antibody that interacts with a specific antigen causing the disease, to obtain measures of certain chemicals that may be as a result of a certain disease and therefore further tests may be required, e.g. Prostate cancer.

Question 15

What diseases can be diagnosed using monoclonal antibodies?

Answer 15

Influenza, hepatitis, and chlamydia.

Question 16

How are monoclonal antibodies used in pregnancy testing?

Answer 16

Testing kits rely on the fact placenta releases the hormone hCG found in the mother’s urine. The monoclonal antibodies present on the test strip are linked to coloured particles. If hCG is present, it binds to the antibodies. The hCG-antibody-colour complex moves along the strip until it is trapped by a different type of antibody, creating a coloured line.

Question 17

What are the ethical issues of the use of monoclonal antibodies?

Answer 17

• Production involves use of mice to produce antibodies and tumour cells, therefore deliberately inducing cancer in mice.
• Some deaths have occurred associated with the use of monoclonal antibodies in the treatment of multiple sclerosis.
• Volunteers taking part in the trial of new monoclonal antibody in 2006 suffered organ failure, possibly ass a result of T cells overproducing chemicals stimulating immune response or attacking body tissues.