antibodies & natural and passive immunity

• antibodies are proteins which bind to antigens to form an antibody-antigen complex
• antibodies are proteins made up of four polypeptide chains, 2 heavy and 2 light. Each chain has a variable and a constant region these chains are connected by disulphide bridges
• what is agglutination?

  antibodies bind to antigens on pathogens cause them to clump together, these clumps are then destroyed by phagocytosis. this makes it easier for phagocytes to engulf more pathogens at a time
• some antibodies work by neutralising toxins released by pathogens
• viruses have spike proteins on their surface which recognise and bind to receptors on the surface of the host cell which allow them entry into the cell. antibodies can bind to these on viruses and stop them attaching to their host cell
• some pathogens can form different strains which often have different antigens, this is called antigenic variation. This means if you are re-infected a second time your body wont have the antibodies
• vaccines give out antigens which allow your body to create memory cells so if the pathogen invades the body again it can produce the according antibodies
• pathogens for vaccines are harmless by:

  • killing but leaving the antigens
  • weaking but leaving antigens unaffected
  • purified antigens removed from the pathogen
  • using inactivated toxins called toxoids that are harmless but trigger the same immune response
• vaccines cause a primary immune response
• why don't vaccines fully eliminate disease?

  • fails to induce immunity in people
  • people get infected before enough antibodies are generated by the vaccine
  • antigenic variability
  • different strains
  • objections to vaccinations (religious)
• what is herd immunity?

  where a population can be protected from a virus if enough people are vaccinated
• What is active immunity?

  stimulation of the production of antibodies by the individuals own immune system. Direct contact with the pathogen or antigen is necessary
• what is passive immunity?

  produced by the introduction of antibodies into individuals from an outside source. No direct contact with the pathogen or antigen is necessary to induce immunity
• natural active immunity- you become immune after catching the disease

  artificial active immunity- you become immune after being given a vaccination
• natural passive immunity-breast milk when your a baby containing antibodies from the mother

  artificial passive immunity- antibodies being transferred by plasma transfusion
• passive immunity is short term as the body makes no memory cells
• active immunity has long term protection because memory cells are produced