Docstoc

immune

Document Sample
immune Powered By Docstoc
					                                The immune response

The immune response is stimulated in the body by antigens. Antigens are foreign,
protein based substances. They are often found attached to the surface of pathogens
such as ………………………………… and …………………………………………

White blood cells

A diagram of a phagocyte:




Phagocytes destroy pathogens by:……………………………………………………………………………………………

……………………………………………………………………………………………………………………………………………………………

A diagram of a lymphocyte:




Lymphocytes produce …………………………………………… which are ………………………………………………

……………………………………………………………………………………………………………………………………………………………

They kill pathogens in several ways.

1. ………………………………………………………………………………………………………………………………………………………

2. ………………………………………………………………………………………………………………………………………………………



B lymphocytes

B lymphocytes multiply to form clones that secrete antibodies when antigens are
detected. This response is slow if the body has not previously encountered the relevant
antigen. Some of these B lymphocytes will remain as memory cells, so if the specific
antigen is introduced to the body again the response will be faster. This can happen
naturally through infection, or artificially through vaccination.
Diagram of B lymphocytes responding to antigens:




T lymphocytes

T lymphocytes have molecules on their surfaces that can recognise specific antigens,
attach themselves to the antigen and destroy it.

Diagram of T lymphocytes responding to antigens:




Immunisation/vaccination

Vaccines contain antigens derived from pathogenic organisms. For example:

1. Using killed bacteria or viruses e.g. ……………………………………………………………………

   Advantage…………………………………………………………………………………………………………………………………

   Disadvantage………………………………………………………………………………………………………………………………
2. Using live non-virulent (not dangerous) strains of bacteria or virus e.g.
   ……………………………………………… and ……………………………………………………
   these non-virulent strains are usually derived from many generations of selective sub
   culturing in the laboratory.

   Advantage…………………………………………………………………………………………………………………………………

   Disadvantage………………………………………………………………………………………………………………………………
3. Chemically modifying a toxin molecule so that it is no longer toxic but still resembles
   the toxin antigenically e.g tetanus or …………………………………………………

4. Separating antigens from the microbe and using them as a vaccine e.g.
   ………………………………………………

   This vaccine is usually only given to ………………………………………… because

   ……………………………………………………………………………………………………………………………………………………

5. Using genetically engineered bacteria to mass produce the relevant antigen e.g.
   …………………………………………………………………………

After someone has been vaccinated, the white blood cells respond by producing
……………………………………………… that will help to defend the body against a future attack by
the infective organism. This is called …………………………………………… immunity.

If a person has been exposed to a dangerous infective organism, antibodies to combat
the infection may be injected to give them immediate protection. This is called
………………………………………………… immunity. An example is:-

……………………………………………………………………………………………………………………………………………………………

……………………………………………………………………………………………………………………………………………………………

Questions on immunity

1) Pasteur found that he could make chickens immune to chicken cholera by giving them
   the bacteria that cause cholera.
   a) What would Pasteur have done to the bacteria before giving it to the chickens?

   ………………………………………………………………………………………………………………………………………………………
   b) How could he get the bacteria into the chickens’ body?

   ………………………………………………………………………………………………………………………………………………………
   c) The chickens’ bodies would respond to the bacteria by

   ………………………………………………………………………………………………………………………………………………………

   d) Pasteur proved his method by giving the chickens live cholera bacteria. Why
      would the chickens not suffer from cholera?

   ………………………………………………………………………………………………………………………………………………………
   e) This type of immunity is called ………………………………………… immunity

   f) A farmer who wanted to save money did not immunise his chickens, but waited
      until they had caught the disease. Explain why this would not save the chickens.

   ………………………………………………………………………………………………………………………………………………………

   ………………………………………………………………………………………………………………………………………………………

2) For hundreds of years, people in Asia had been scratching their skin and rubbing a
   small amount of matter from the wounds of a person suffering from a mild form of
   smallpox into the scratch. Many people survived smallpox epidemics.
   a) Explain the theory behind this activity.

   ………………………………………………………………………………………………………………………………………………………

   ………………………………………………………………………………………………………………………………………………………

   b) Describe what happens when the immune response is triggered for the first time
      in a person.

   ………………………………………………………………………………………………………………………………………………………

   ………………………………………………………………………………………………………………………………………………………

   ………………………………………………………………………………………………………………………………………………………

   ………………………………………………………………………………………………………………………………………………………
   c) It is often said that you can only suffer once from diseases such as measles.
      Explain why.

   ………………………………………………………………………………………………………………………………………………………

   ………………………………………………………………………………………………………………………………………………………

   d) Immunity to chickenpox does not give you immunity to measles. Why not?

   ………………………………………………………………………………………………………………………………………………………

   ………………………………………………………………………………………………………………………………………………………

				
DOCUMENT INFO