IMMUNE SYSTEM

• ANTIGENS = foreign protein that stimulates antibody production
• ANTIBODY= A protein produced by by B cells/plasma cells that is specific to 1 antigen.

  • Y shaped structure with 2 heavy chains and 2 light chains
  • They bind to antigens and destroy or inhibit it
• NATURAL ACTIVE IMMUNITY (immunity after getting ill)

  • Req exposure to antigen
  • Takes a while for protection to dev
  • Memory cell produced
  • Long term protection
• NATURAL PASSIVE IMMUNITY (antibodies made by diff organism eg. placenta )

  • Doesn't req exposure to antigen
  • immediate protection
  • memory cells not produced
  • short term protection as antibodies are broken down
• VACCINATION - injecting dead, weakened or killed pathogens so the immune system can produce memory cells without causing disease.
• ARTIFICIAL ACTIVE IMMUNITY (eg vaccine) = immune after vaccination containing an antigen
• ARTFICIAL PASSIVE IMMUNITY (eg blood transfusion) = immunity from receiving antibodies from another person
• NON SPECIFIC DEFENCES = defences against all types of microorganisms
• Lymphocytes are made in?

  Bone marrow
• IMMUNE RESPONSE

  1. PHAGOCYTOSIS
  2. T CELLS
  3. B CELLS
• IMMUNE RESPONSE- PHAGOCYTOSIS

  • Phagocytes (eg macrophage & neutrophil) recognise foreign antigens on pathogen
  • engulf pathogen by formation of vesicle followed by fusion with lysosomes
  • Lysozymes then hydrolyse
  • Phagocytes then present pathogens antigens
• IMMUNE RESPONSE - T CELLS

  • T cells recognise antigen via receptor proteins and bind to complementary antigen
  • T cells activate cytotoxic T cells and stimulate B cells to divide and secrete antibodies
  • Cytotoxic T cells kill abnormal cells & infected body cells via perforin
  • T memory cells can also be produced which remain in blood and provide long term protection
• IMMUNE RESPONSE- B CELLS

  • Clonal selection occurs as a result of T cells and B cell antibodies binding to specific complementary antigen
  • Activated B cell divides into plasma cell which secretes antibodies specific to antigen
  • Phagocytes will bind to antibodies and are destructed
  • Memory B cells remain in blood and provide long term protection
• CELLULAR IMMUNITY PROCESS= Phagocytosis, T cells and what they differentiate into
• HUMORAL IMMUNE RESPONSE= B cells, clonal selection and production of antibodies
• PRIMARY RESPONSE= Pathogen is infecting body for the 1st time so response is slow as not many B cells available and memory cells not produced yet
• SECONDARY RESPONSE= Same pathogen renters body & clonal selection happens faster meaning no symptoms show
• What may happen to vaccines taken orally?

  be broken down by enzymes in the gut or be too big to be absorbed
• Why are booster vaccines given?

  • Make sure memory cells are produced
  • if 1 dose doesn't contain enough antibodies to be effective
• HERD IMMUNITY= when significant amount of population has been vaccinated providing protection for those that haven't been vaccinated
• ANTIGENETIC VARIATION

  • When pathogens mutate to change surface antigens
  • Means that even if you have been infected with that pathogen before, body will still have a primary response
  • Makes it harder for vaccines to be produced
• MONOCLONAL ANTIBODIES

  • antibodies that all have the same tertiary structure and are produced from genetically identical B cells
  • Can differentiate into any type of cell to bind to anything
  • Very specific as binding site has unique tertiary structure
  • USES: Block antigens on cells & target drugs to specific cells eg. in ELISA tests
• ELISA TESTS = Used to see if someone has antibodies against a certain pathogen/antigen
• INDIRECT ELISA= Uses 2 diff types of antibodies eg. HIV Test
• DIRECT ELISA= Uses single antibody complementary to antigen your looking for
• Describe how to test for HIV

  1. (indirect elisa)
  2. Antigens for disease you are looking for are bound to bottom of a dish
  3. Patients blood is added. If it contains the antibodies complementary to the antigen on plate, they will bind
  4. Blood is washed off
  5. 2nd antibody attached to an enzyme is added that will bind to any antibody present on the plate and is then rinsed to remove any unbound antibodies
  6. Substrate added which is able to react with enzyme on the second antibody to produce a colour. Colour change indicates a positive test
• Targeting drugs to specific cell type eg cancer

  1. Cancer cells have antigens called tumour markers that reg. cels don't have
  2. Monoclonal antibodies can be used to bind onto these or have anti-cancer drugs attached to them
  3. Antibodies come into contact with cancer cells and bind to markers to rel. drug
  4. Drug will only accumulate in body where there are cancer cells, as antibodies only specific to cancer antigen (tumour markers) which reduces side effects
• Targeting substances for medical diagnosis eg. pregnancy test

  -Pregnancy in women indicated by presence of hCG

  1. Application area contains antibodies for hCG bound to a blue bead
  2. When urine is applied to area, any hCG will bind to the bead forming antigen-antibody complex
  3. Urine moves up towards test strip carrying beads
  4. Test strip contains immobilised antibodies for hCG
  5. If hCG is pos then test strip will turn blue as immobilised antibody will bind to hCG. If neg beads will pass through and no colour change occurs
•   Explain why the number of HIV particles in the blood

       rises during the first few months after infection

  HIV is entering and infecting new cells to make new viruses

  cells release virus into blood
•  State role of a helper T cell.

  • stimulate cytotoxic t cells
  • stimulate b cells
• Describe the role of tRNA in translation.

   Anticodon on tRNA binds to complementary codon on mRNA     

   tRNA brings/carries specific amino acid to ribosome
• Explain why viruses are described as acellular and non-living.

  • acellular
  • can't carry out own metabolic reactions
• Give one reason why antibiotics are not effective against viruses.

  viruses don't have own metabolic reactions or structures, need a host cell
•  What is an antigen?

  protein on cell surface membrane that stimulates immune response
• The antivenom did not give the zookeeper lasting protection against this snake venom. Explain why.

  Zookeeper is not producing antibodiesNo memory cells made