Antibodies

Question 1

what are antibodies?

Answer 1

• proteins with specific binding sites synthesised by B cells
• the massive variety of antibodies is possible because they are made of proteins that occur in an infinite number of forms

Question 2

what do antibodies do when the body is infected by non self material?

Answer 2

-a B cell produces a specific antibody which reacts with an antigen on the surface of the non self material by binding to them

Question 3

what is the structure of antibodies?

Answer 3

• each antibody binding sites that are complementary to a specific antigen forming an antigen antibody complex
• the biding site is different depending of the antibody so its called a variable region
• they are made from four polypeptide chains
• the chains of one pair are long and called heavy chains while the chains of the other pair are shorter and known as light chains
• each binding site on the antibody consists of a sequence of amino acids form a specific 3D shape that binds directly to a specific antigen
• the rest of the antibody is known as the constant region which binds to receptors on the cells like B cells

Question 4

what are monoclonal antibodies?

Answer 4

• bacterium or other microorganism entering the body is likely to have hundreds of different antigens on its surface
• each antigen will induce a different B cell to multiply and form a clone of itself
• each clone will produce a different antibody
• its of considerable medical value to be able to produce antibodies outside the body
• its even better if a single type of antibody can be isolated and cloned

Question 5

what are monoclonal antibodies used for?

Answer 5

• therapeutic drugs
• medical diagnosis
• pregnancy testing

Question 6

what is direct monoclonal antibody therapy?

Answer 6

-as an antibody is very specific to particular antigen monoclonal antibodies can be used to target specific substances and specific cells like cancer cells

Question 7

what is Herceptin?

Answer 7

• a monoclonal antibody used to treat breast cancer
• the advantage of direct monoclonal antibody therapy is that since the antibodies are not toxic and are highly specific they lead to fewer side effects than other forms of therapy

Question 8

what is indirect monoclonal antibody therapy?

Answer 8

• it involves attaching a radioactive or cytotoxic drug to the monoclonal antibody
• when the antibody attaches to the cancer cells it kills them

Question 9

why are monoclonal antibodies referred to as magic bullets?

Answer 9

-they can be used in small doses to target specific sites which is cheaper and reduces the Side effects the drug might have

Question 10

how are monoclonal antibodies used in medical diagnosis?

Answer 10

• they are used to diagnose influenza, hepatitis and chlamydia infections and some cancers
• men with prostate cancer for example often produce more of a protein called prostate specific antigen leading to unusually high levels in the blood
• using a monoclonal antibody that interacts with this antigen its possible to obtain a measure of the level of PSA in a sample of blood
• a higher level of PSA can give an early warning of the disease

Question 11

how are monoclonal antibodies used in pregnancy testing?

Answer 11

• at home pregnancy tests rely on the fact that the placenta produces a hormone called human chronic gonadotropin and that this is found in the mothers urine
• monoclonal antibodies present on the test strip are linked to coloured particles
• if hCG is present in the urine it binds to these antibodies the hCG antibody colour complex moves along the strip until its trapped by a different type of antibody creating a coloured line

Question 12

what are the ethical issues of using monoclonal antibodies?

Answer 12

• production of monoclonal antibodies involves the use of mice to produce antibodies and tumour cells through deliberately inducing cancer
• monoclonal antibodies have been used successfully to treat diseases like lung cancer and diabetes which has saved many lives however some patients who died due to multiple sclerosis has been linked to this treatment meaning patients should know the full risks and benefits before using the drug
• testing the safety of new drugs can be dangerous as I n London 6 volunteers tool part in a trial of monoclonal antibody and within minuets suffered multiple organ failure due to T cells over producing chemicals that stimulate an immune response or attacking body tissues
• although all survived this process is far from safe