6. Antibodies and Antibiotics Flashcards
What are antibodies made by?
lymphocytes (one of the two main types of white blood cell)
What are antigens?
foreign substances that stimulate the production of antibodies
How many types of antibodies can a lymphocyte make? What does this mean for the number of lymphocytes?
- can only make one type of antibody
- therefore a huge number of different lymphocyte types is needed
What does the lymphocytes do with (some) of the antibodies it makes (whilst the body is yet to recognise an antigen)?
- lymphocyte puts some of the antibody that it can make into its cell surface membrane with the antigen-combining site projecting outwards
What happens when a pathogen enters the body?
its antigens bind to the antibodies in the cell surface membrane of one type of lymphocyte
What happens when antigens bind to the antibodies on the surface of a lymphocyte?
this lymphocyte becomes active and divides by mitosis to produce a clone of many identical cells
What are the cells produced by mitosis of a lymphocyte called? What do these cells produce?
- plasma cells
- large quantities of the same antibody that bind to the antigens on the surface of the pathogen and stimulates its destruction
What is ‘specific immunity’. Explain.
- production of antibodies by lymphocytes
- because different antibodies are needed to defend against different pathogens
What happens after a pathogen has been cleared from the body? Why is this useful?
- 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
What does HIV stand for?
human immunodeficiency virus
How does HIV affect the human host?
- 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
What does AIDS stand for?
acquired immunodeficiency syndrome
What does AIDS lead to if not treated?
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)
How is HIV transmitted?
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
What are antibiotics?
chemicals produced by microorganisms, to kill or control the growth of other organisms
Give an example of an organism that produces an antibiotic.
Penicillium nostatum
- produces penicillin that kills bacteria
How do antibiotics work?
by blocking processes that occur in prokaryotic cells but not eukaryotic cells
Why can viruses not be treated by antibiotics?
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
Can bacteria be treated with antibiotics?
most can, but some have acquired genes that confer resistance to an antibiotic and some strains of bacteria now have multiple resistance
Who was Penicillin developed as an antibiotic? When? How did they first test it?
- 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
How did the first test on a human subject go?
- 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.
How would the modern day scientist/ethics committee regard Florey and Chain’s work? What would be done nowadays?
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
