Im,une system

• • Defects in the immune system mean that an individual is more likely to suffer from infectious diseases. For instance, human immunodeficiency virus infections, known as HIV, which leads to AIDS, affect the immune system and lead to an increase in susceptibility to infectious diseases.
• • The reaction of the immune system to pathogens and other foreign bodies can trigger allergic reactions that lead to skin rashes and asthma. For instance, severe respiratory infections in babies can lead to asthma in later childhood.
• If pathogens pass the non-specific first line of defence they will cause an infection. However, the body has a second line of defence to stop or minimise this infection. This is called the immune system. As a part of this there are two types of white blood cell called phagocytes and lymphocytes.
• Phagocytes are white blood cells. They are attracted to pathogens. They surround them in the blood, bind to them and engulf them.
• The phagocytes' membrane surrounds the pathogen and the enzymes found inside the cell, then break down the pathogen in order to destroy it. As phagocytes do this to all pathogens that they encounter, we call them 'non-specific
• Lymphocytes are another type of white blood cell.

  1. They recognise proteins on the surface of pathogens called antigens
  2. . Lymphocytes detect that both the proteins and pathogens are foreign, not naturally occurring within your body and produce antibodies.
  3. This can take a few days, during which time you may feel ill. The antibodies created by the lymphocytes cause pathogens to stick together, and make it easier for phagocytes to engulf them
• memory lymphocytes

  1. first time ur infected you quite ill because your body takes time to identify and destroy the pathogen
  2. meanwhile your body develops memory lymphocytes(cell)
  3. you don't get quite as ill the second time because your immune system responds quickly
• memory lymphocytes

  • special type of white blood cells that remember the pathogen
• why are lymphocytes that produce antitoxins are called 'specific'


  Some pathogens produce toxins which make you feel ill. Lymphocytes can also produce antitoxins to neutralise these toxins. Both the antibodies and antitoxins are highly specific to the antigen on the pathogen
• antigen(proteins on surface of pathogen)


  any substance which is foreign to body so antibodies are produced by immune system against it e.g. toxins
• antibody


  protein produced by white blood cell that binds to specific antigens can act as signal to immune system to destroy antigen(or pathogen its part of)
• 1.  Immunisations allow an inactive pathogen into the body, which contain a specific antigen2. memory lymphocytes remain in blood and remebr right antibodies to make in response to inactive pathogen
  2. this means lymphocytes can react quickly to pathogen in future
• Antibiotics damage the bacterial cells by inhibiting their cellular processes, but do not damage the host cells. They have the ability to cure some bacterial diseases that would have previously killed many people. Since their introduction, they have had a large influence on the world's health and death rate.
• Different bacteria cause different diseases. One antibiotic may only work against one type of bacteria, or a few types. This means that a range of different antibiotics is needed for the treatment of the whole range of bacterial diseases.
• what does vaccine contain?

  Small quantities of dead, weakened, or inactive forms of a pathogen
• How do vaccines work?

  They expose us to the antigens of a pathogen so that we can develop immunity to it
• HERD IMMUNITY


  As a result, the whole population becomes protected - not just those who are immune.
• potential drawbacks of vaccine

  • They can (in rare cases) cause severe reactions such as seizures
  • They can cause mild symptoms such as fever or a sore arm
  • They don't always give full immunity to the disease 
• stages of drug development

  1. Stage 1 - Test the drug on human  and tissues.
  2. Stage 2 - Test the drug on live .
  3. Stage 3a - Test the drug on healthy  to find the  dosage before side effects occur.
  4. Stage 3b - Test the drug on patients that suffer from the relevant disease, to find the  dosage. 
• Why is it important that new medicinal drugs undergo testing before they are used?

  To make sure they are an effective treatment

  To determine the optimum dose

  To make sure they are safe to use
• placebo


  A substance or treatment that contains no active drug