6. Antibodies and Antibiotics

Question 1

What are antibodies made by?

Answer 1

lymphocytes (one of the two main types of white blood cell)

Question 2

What are antigens?

Answer 2

foreign substances that stimulate the production of antibodies

Question 3

How many types of antibodies can a lymphocyte make? What does this mean for the number of lymphocytes?

Answer 3

• can only make one type of antibody

- therefore a huge number of different lymphocyte types is needed

Question 4

What does the lymphocytes do with (some) of the antibodies it makes (whilst the body is yet to recognise an antigen)?

Answer 4

• lymphocyte puts some of the antibody that it can make into its cell surface membrane with the antigen-combining site projecting outwards

Question 5

What happens when a pathogen enters the body?

Answer 5

its antigens bind to the antibodies in the cell surface membrane of one type of lymphocyte

Question 6

What happens when antigens bind to the antibodies on the surface of a lymphocyte?

Answer 6

this lymphocyte becomes active and divides by mitosis to produce a clone of many identical cells

Question 7

What are the cells produced by mitosis of a lymphocyte called? What do these cells produce?

Answer 7

• plasma cells
• large quantities of the same antibody that bind to the antigens on the surface of the pathogen and stimulates its destruction

Question 8

What is ‘specific immunity’. Explain.

Answer 8

• production of antibodies by lymphocytes

- because different antibodies are needed to defend against different pathogens

Question 9

What happens after a pathogen has been cleared from the body? Why is this useful?

Answer 9

• most of the lymphocytes disappear, but some persist as memory cells
• memory cells can quickly reproduce to form a clone of plasma cells if a pathogen carrying the same antigen is re-encountered

Question 10

What does HIV stand for?

Answer 10

human immunodeficiency virus

Question 11

How does HIV affect the human host?

Answer 11

• infects a type of lymphocyte that plays a vital role in antibody production
• over a period of years these lymphocytes are gradually destroyed
• without active lymphocytes, antibodies cannot be produced
• this condition is called AIDS

Question 12

What does AIDS stand for?

Answer 12

acquired immunodeficiency syndrome

Question 13

What does AIDS lead to if not treated?

Answer 13

death from infections by a variety of pathogens that would normally be controlled easily (but can’t be controlled because the body has too few lymphocytes)

Question 14

How is HIV transmitted?

Answer 14

transferred through body fluids from an infected person to an uninfected one:

• through small cuts or tears in vagina, penis, mouth or intestine during vaginal, anal or oral sex
• in traces of blood on hypodermic needles shared by intravenous drug abusers
• across the placenta from a mother to a baby, or through cuts during childbirth or in milk during breast-feeding
• in transfused blood or with blood products such as Factor VII used to treat hemophiliacs

Question 15

What are antibiotics?

Answer 15

chemicals produced by microorganisms, to kill or control the growth of other organisms

Question 16

Give an example of an organism that produces an antibiotic.

Answer 16

Penicillium nostatum

- produces penicillin that kills bacteria

Question 17

How do antibiotics work?

Answer 17

by blocking processes that occur in prokaryotic cells but not eukaryotic cells

Question 18

Why can viruses not be treated by antibiotics?

Answer 18

viruses lack a metabolism and instead rely on a host such as a human cell to carry out metabolic processes

• it is not possible to block these processes using an antibiotic without also harming human cells
• therefore, diseases cannot be treated with antbiotics

Question 19

Can bacteria be treated with antibiotics?

Answer 19

most can, but some have acquired genes that confer resistance to an antibiotic and some strains of bacteria now have multiple resistance

Question 20

Who was Penicillin developed as an antibiotic? When? How did they first test it?

Answer 20

• Florey and Chain
• late 1930s
• first test on 8 mice infected with a bacterium that causes a fatal pneumonia
• all 4 treated mice recovered; all 4 untreated mice died

Question 21

How did the first test on a human subject go?

Answer 21

• initially, they only had small quantities of relatively impure penicillin
• the infected (septicemia) man started to recover, but the antibiotic ran out. He died.
• 5 patients were then tested, all of whom were cured.

Question 22

How would the modern day scientist/ethics committee regard Florey and Chain’s work? What would be done nowadays?

Answer 22

would not be regarded as safe: put humans at risk

• extensive animal testing of new drugs is first done to check for harmful effects
• after this small and then larger doses are tested on healthy, informed humans to see if the drug is tolerated
• only then is the drug tested on patients with the disease and if small scale trials suggest that it is effective, larger scale double-blind trials are carried out on patients to test the drug’s effectiveness and look for rare side effects