ELISA TEST

• what does ELISA stand for?

  enzyme linked immunosorbent assay
• other than HIV, what are ELISA's used to test for?

  prostrate cancer

  clinical diseases

  food testing

  drug testing
• what is an ELISA used to test for?

  used to detect antibodies or specific antigens
• Explain how to use an ELISA to test for a specific antigen?

  1. container coated with monoclonal antibodies
  2. wash to remove any excess/unbound antibodies
  3. sample to be tested (e.g. blood/urine) is added to container - if the specific antigen is present it will bind to the antibodies
  4. wash to remove any unbound antigens
  5. a second antibody of the same type, with an enzyme attached is added - this binds to the antigens
  6. sample washed
  7. the substrate for this enzyme is then added, substrate is hydrolysed by the enzyme on the second antibody producing a colour change - indicating a positive result
• what triggers the colour change in an ELISA test?

  the substrate on the enzyme attached to the second antibody causes the substrate to be hydrolysed indicating a colour change + positive result.
• what alternative variations exist in ELISA test (indirect)?

  • container coated with antigens, and the sample added may contain specific antibodies that bind to the antigen
• what is the role of the second antibody in an ELISA?

  the second antibody, with an enzyme attached binds to the antigen present in the sample
• How do ELISA tests detect the presence of a specific antigen?

  If the specific antigen is present, it will bind to the antibodies in the container.
• how can this test detect the amount of antigen present in the sample?

  • if more antigen is present, more antigen - antibody complexes
  • more 2nd antibody with enzyme attached will be present
  • more enzyme - substrate complexes form, more coloured product