Immunity

• what are pathogens?


  any microorganism that causes diseases
• what can lymphocytes detect?

  • abnormal body cells
  • pathogens
  • cells from other humans
  • toxins
• define a lymphocyte


  A type of white blood cell that identifies non-self cells
• what are molecules found of the cell surface membrane?

  • glycolipids
  • proteins
  • cholesterol
  • glycolipids
• define antigen


  a protein in the cell surface membrane that triggers an immune response
• what do lymphocytes trigger?

  a specific immune response
• what are lymphocytes able to recognise and explain

  antigens

  because they have complementary receptors that bind to antigens on non-self cells
• what do the receptors on the lymphocytes do?

  they recognise one specific antigen because they have receptors that are complementary to antigens on non-self cells
• what do phagocytes trigger?

  a non-specific immune response because they are able to recognise all pathogens
• what do phagocytes destroy?

  pathogens by carrying out phagocytosis
• what doe phagocytes do?

  Engulf pathogens - destroy them using lysosomes. Then become APCs.
• what doe APC do?

  present pathogenic antigens on its own cell membrane signalling T lymphocytes
• what doe T helper do?

  stimulates:

  • cytotoxic T cells
  • B cells
  • Phagocytosis
  • memory T cells
• what do cytotoxic T cell do?

  kill infected cells through the release of an enzyme that kills the cell or tumour.
• define monoclonal antibody


  Antibodies with the same tertiary structure
• Describe and explain the role of antibodies in stimulating phagocytosis.

  Bind to antigen

  Attract phagocytes
• What is an antigen?

  A foreign protein

  that stimulates an immune response
• What is an antibody?

  A protein specific to an antigen

  Produced by B cells
• Describe how antibodies lead to the destruction of a pathogen.

  Antibodies bind to complementary antigens on the surface of the pathogen, forming antibody-antigen complexes. This causes pathogens to clump together in a process called agglutination, which makes it easier for phagocytes to engulf and destroy pathogens.
• Describe the different ways that the specific immune response leads to the destruction of antigens.

  B cell clones differentiate into plasma cells, which secrete antibodies. Antibodies bind to antigens on pathogens, causing them to agglutinate. This makes it easier for phagocytes to engulf and destroy foreign antigens.Helper T cell clones stimulate phagocytes to destroy antigens by phagocytosis. They also stimulate cytotoxic T cells to secrete perforin, which kills infected cells and destroys the antigens within them.
• what is herd immunity?

  large proportion of population vaccinated reducing spread of pathogen

  • large population immune, so don't become ill from infection.
  • fewer infected people to pass pathogen on OR unvaccinated people less likely to come into contact with someone with the disease
• what is a vaccine?

  injected with an antigen from attenuated (weak/dead) pathogens
• what does a vaccine stimulate?

  formation of memory cells
• what is the primary response?

  first exposure to antigen

  antibodies produced slowly and at a lower conc.

  take time for specific B plasma cells to be stimulated to produce specific antibodies

  memory cells produced
• what is the secondary response?

  second exposure

  antibodies produced faster and higher conc.

  B memory cells undergo mitosis rapidly to produce many plasma calls which produce specific antibodies
• diagram of the primary and secondary response


  diagram:

  
• describe the vaccine process

  1. specific B lymphocyte with complementary receptor binds to the antigen
  2. specific T helper cells binds to APC and stimulates B cell
  3. B cell divides by mitosis to form clones
  4. some differentiate into B plasma cells which release antibodies
  5. some differentiate into B memory cells
  6. During secondary exposure to antigen. B memory cells divide rapidly by mitosis to produce B plasma cells
  7. Release antibodies faster a higher rate
• Define herd immunity


  When large numbers of the population are vaccinated, so very few people carry the pathogen. This means that vulnerable people are less likely to make contact with infected people.
• Why can it be difficult to eradicate a disease even after a vaccine is developed?

  Over time, the pathogen could undergo a mutation which changes the pathogen’s antigens. This means the antibodies produced in response to the vaccine won’t be complementary to the pathogen.
• What are the issues associated with vaccines?

  • tested on animals
  • dangerous side effects
  • debate about whether they should be made compulsory
• Describe the process of HIV replication. 

  • once HIV has entered the bloodstream, an attachment protein binds to a helper T cell. 
  • HIV’s protein capsid fuses with the helper T cell membrane, allowing viral RNA and enzymes to enter the T cell. 
  • reverse transcriptase (enzyme) converts the viral RNA into DNA.
  • viral DNA enters the helper T cell’s nucleus, where it’s integrated into the host cell’s DNA.
  • viral DNA is transcribed to produce viral mRNA.
  • viral mRNA leaves the nucleus and is translated to produce viral proteins.
  • viral proteins form a new HIV, which breaks away from the helper T cell. 
• what are pathogens made of?

   biological molecules, such as proteins and carbohydrates, which are formed by condensation reactions.