Monoclonal antibodies

• What are monoclonal antibodies?

  Antibodies produced by plasma cells from one B-cell clone
• Why are monoclonal antibodies useful?

  They can be produced outside the body and are specific to one type of antigen
• What are the three main medical uses of monoclonal antibodies?

  Targeted medication, pregnancy testing, medical diagnosis (ELISA)
• How are monoclonal antibodies used in radioimmunotherapy?

  They deliver radiation to specific cancer cells by binding to antigens on them
• What is the advantage of monoclonal antibodies in radioimmunotherapy?


  It reduces the amount of radiation reaching healthy tissue and side effects
• How do monoclonal antibodies help find tumours in the body?

  They seek out antigens found on cancer cells and deliver treatment to those sites
• What protein do pregnancy tests detect?

  hCG (human chorionic gonadotropin)
• How do antibodies work in a pregnancy test?

  Antibodies bound to coloured beads bind to hCG in urine
• What creates the first 'blue line' in a pregnancy test?

  Immobilised antibodies that bind to hCG that will be attached to the mobile antibodies
• What creates the second 'blue line' in a pregnancy test if hCG is present?


  Immobilised antibodies that bind to the coloured beads on the mobile antibodies
• How does the second blue line show that the test has run correctly?

  It shows that the mobile antibodies with the blue beads have been transported all the way up the test strip.
• What does ELISA stand for?

  Enzyme Linked ImmunoSorbent Assay
• What is the purpose of the ELISA test?

  To detect the presence of antigens or antibodies
• What is the function of the enzyme in the ELISA test?

  It reacts with a substrate to produce a colour change
• Why is there a washing step in the ELISA test?

  To remove unbound antibodies and enzymes
• What indicates the presence of more antigen in an ELISA test?

  A stronger colour change indicates more antigen is present
• What is the difference between direct and indirect ELISA?

  Direct involves one antibody, used to look for an antigen in a sample and indirect involves multiple antibodies and is usually used to look for the presence of an antibody
• What is direct ELISA used to detect?

  The presence of an antigen in a sample
• What is added in indirect ELISA after the sample is checked for antibodies?

  A second antibody with an enzyme bound to it
• Why can indirect ELISA be more sensitive than direct ELISA?

  Because it uses multiple antibodies
• What is the risk associated with indirect ELISA?

  Cross-reactivity with the antigen, leading to higher background readings
• Why does indirect ELISA take longer than direct ELISA?

  It involves an extra washing step and the extra step of adding a second antibody
• What is an advantage of using indirect ELISA?

  The same secondary antibody can be used for multiple assays
• How does the enzyme produce a colour change in the ELISA test?

  By reacting with a substrate
• What medical conditions can be diagnosed using the ELISA test?

  HIV infection or allergies
• What type of antibodies are used in indirect ELISA?

  Secondary antibodies with enzymes attached
• What are monoclonal antibodies used for?

  To target specific substances and specific cells. E.g. cancer cells
• What happens during direct monoclonal antibody therapy?

  • Monoclonal antibodies are produced that are specific to antigens on cancer cells
  • These antibodies are given to a patient and attach themselves to receptors on the cancer cells
  • They attach to the surface of the cancer cells and block the chemical signals that stimulate their uncontrolled growth
• What are the advantages of direct monoclonal antibody therapy?

  Since monoclonal antibodies are not toxic & are highly specific, they have fewer side effects than other cancer treatments
• What does indirect monoclonal antibody therapy involve?

  Involves attaching a radioactive or cytotoxic drug (a drug that kills cells) to the monoclonal antibody. When the antibody attaches to the cancer cells, it kills them.
• What are the advantages if indirect monoclonal antibody therapy?

  Can be used in smaller doses.
• How are monoclonal antibodies used for medical diagnosis?

  • Used for the diagnosis of influenza, hepatitis, chlamydia as they produce more rapid results than other methods
  • Can also be used to diagnose some cancers E.g. prostate cancer
• How do pregnancy tests work?

  • At home pregnancy tests rely on the placenta producing the HCG hormone which can be found in the mother's urine
  • If HCG is present, it binds to the antibodies in the test strip
  • The HCG-antibody-colour complex moves along the strip until it is trapped by a different type of antibody creating a coloured line.
• What are the ethical issues of using monoclonal antibodies?

  • Production involves mice and involves deliberately inducing cancer in mice -> some people object to animals being used in this way (although there are guidelines in place to minimize suffering)
  • There have been some deaths associated with monoclonal antibodies and their use in the treatment of multiple sclerosis