cell recognition and the immune system

• describe a phagocyte


  - a type of white blood cell that carries out phagocytosis

  - found in the blood and tissues
• describe an antigen


  - cell-surface molecule which is recognised as non-self which stimulates an immune responses
• describe phagocytosis


  1)a phagocyterecognisestheforeign antigenson a pathogen2)the cytoplasm of the phagocyteengulfsit by endocytosis3)the pathogen is contained aphagocytic vacuolein the cytoplasm of the phagocyte4)alysosome fuseswith the phagocytic vacuole. thelysozymesbreak down the pathogen5)the phagocytesticks the antigen on its surfaceto activate other immune system cells

  
• what does the immune system use antigens for?

  to identify:

  - pathogens

  - abnormal body cells that have abnormal antigens on their surface

  - toxins

  - cells from other individuals of the same species
• describe a T cell (T-lymphocyte)


  a type of white blood cell that has receptor proteins on its surface that bind to complimentary antigens on phagocytes
• what is the role of helper T-cells? (Th cells)

  - they release chemical signals that stimulate phagocytes and cytotoxic T-cells which kill abnormal and foreign cells

  - they activate B-cells which secrete antibodies
• describe a B-cell (B-lymphocytes)


  - a type of white blood cell that have antibodies on their surface

  - each have a different shaped antibody on its membrane
• what is an antibody?

  a protein that binds to a specific antigen to form an antigen-antibody complex to stimulate an immune response
• describe the B-cell immune response

  1) the antibody on the B-cell binds to the complementary antigen in the pathogen

  2) Helper T-cells attach to the antigens on the B cells, activating the B cell to divide via mitosis to create plasma cells
• describe how plasma cells destroy pathogens

  1) cloned plasma cells secrete antibodies specific to the antigens on the pathogen's surface

  2) the antibody attaches to the antibody and destroys it

  3) some B cells develop into memory cells
• How does agglutination occur?

  - an antibody has 2 binding sites so they can bind to 2 pathogens at a time

  - so the pathogens become clumped together

  - then phagocytosis occurs
• what are antibodies made of?

  4 polypeptide chains

  - chains of one pair are long and called heavy chains

  - chains of the other pair are short and are called light chains
• describe the variable region on an antibody

  it has a unique tertiary structure that's complementary to one specific antigen
• all antibodies have the same what?

  constant regions
• draw an antibody

  
• what are the 2 types of immune responses?

  cellular and humoral
• describe the cellular immune response

  the T-cells and the immune system cells that they interact with
• describe the humoral immune response

  B cells, clonal selection and the production of monoclonal antibodies from the humoral response
• describe the primary immune response

  When an antigen enters the body for the first time and activates the immune system
• why is the primary immune response slow?

  - There aren't many B-cells that can make the antibody needed to bind to it

  - eventually enough antibodies will be produced to overcome the infection

  - the infected person will show symptoms
• what produces memory cells after infection?

  T cells and B cells
• what is the function of memory T cells?

  remember the specific antigen
• what is the function of memory B cells?

  record the specific antibodies need to bind to the antigen
• how does secondary immune response differ from the primary immune response?

  secondary immune response is:

  - quicker

  - produces more antibodies
• describe the secondary immune response

  - clonal selection happens faster

  - memory B cells are activated and divide into plasma cells that produce the specific antibody

  - memory T cells are activated and divide into the correct type of T cells to kill the cell carrying the antigen

  - often the pathogen is destroyed before you show any symptoms
• how do vaccines make you immune?

  vaccines carry antigens that cause your body ti produce memory cells against a specific pathogen without the pathogen causing disease
• hoe does herd immunity work?

  - vaccines protected individuals from the disease so they reduce its occurrence

  - those unvaccinated are less likely to catch the disease
• how are antibodies found in vaccines?

  contain antigens the are free or attached to a dead or attenuated pathogen
• what 2 ways can vaccines be given?

  - injection

  - orally
• what are the limitations if taking vaccines orally?

  - the vaccine can be broken down by enzymes in the gut

  - the molecules of the vaccine are too big to be absorbed into the blood
• why are booster vaccines given?

  to make sure that memory cells are produced
• what activates the primary immune response?

  antigens on the surface of pathogens
• describe antigenic variation


  - some pathogens change their surface antigens

  - in secondary infection the memory cells will not recognise the antigens

  - so a slower primary immune response has to be carried out
• describe how antigenic variation affects the influenza vaccine

  - the antigens on the influenza virus changes forming new strains of the virus that are immunologically distinct

  - new vaccines are developed and one is chosen that is most effective against the latest strain

  - gov and health authorities implement vaccine programs
• define a monoclonal antibody

  antibodies produced from a single group of genetically identical B cells
• describe how monoclonal antibodies are used in cancer treatments

  - cancel cells have tumour markers that are not found on normal body cells

  - monoclonal antibodies are made that bind to tumour markers, anti-cancer drugs can also be attached to the antibodies

  - the drug only accumulates where there are cancer cells

  - so the side effects of an antibody based drug are less than other drugs because the accumulate near specific cells

  
• describe active immunity


  when your immune system makes its own antibodies after being stimulated by an antigen
• what are the 2 types of active immunity?

  natural

  = when you become immune after catching a disease

  artificial = when you become immune after you've been given a vaccination
• describe passive immunity


  being given antibodies made by a different organism
• describe the 2 types of passive immunity

  natural = when a baby becomes immune due to the antibodies it receives from it mother through the placenta and breast milk

  
  

  artificial = becoming immune after being injected with antibodies made from someone else