3.2 Monoclonal antibodies (HT only)

• What is the difference between antibodies and antigens?

  ● Antibodies are proteins produced by a type of white blood cell called a lymphocyte

  ● Antibodies bind to specific antigens (on specific cells eg. pathogens / cancer cells or a specific chemical)
• What are monoclonal antibodies (mAbs)?

  ● Antibodies (proteins) produced from a single clone of cells (so they are identical)

  ● Specific to one binding site on one protein antigen (so only bind to this antigen)

  ○ So can target a specific chemical (eg. a hormone) or specific cells (eg. cancer cells) in the body
• whats wrong with this statement

  "The hybridoma cell is the monoclonal antibody and is given as treatment.”

  Clones of a single hybridoma cell produce the monoclonal antibody. This is collected and purified to be given as treatment.
• A farmer thinks a potato crop is infected with potato virus Y (PVY). They obtain a monoclonal antibody test kit for PVT. To make the monoclonal antibodies a scientist first isolates the PVY protein from the virus. Describe how the scientist would use the protein to produce the PVY monoclonal antibody. (4)

  1. Inject protein into a mouse
  2. Combine lymphocytes with tumour cells to make hybridoma cells
  3. Find a hybridoma which makes a monoclonal antibody specific to PVY
  4. Clone hybridoma to produce many cells (to make the antibody)
• Monoclonal antibodies are produced from a single clone of cells. Give two advantages of cloning an antibody-producing cell. (2)

  ● All antibodies are identical

  ● Large amount of antibodies can be produced
• Why are monoclonal antibodies not yet as widely used as everyone hoped when they were first developed?

  Create more side-effects than originally expected (as made from mouse lymphocytes).
• Why is this statement wrong?

  "Binding of a monoclonal antibody alone to a cancer cell will stop it growing and dividing."

  A monoclonal antibody can be used as a cancer treatment if attached to a toxic drug.
• Why is this statement wrong?

  “Monoclonal antibodies can only bind to antigens on pathogens.”

  Monoclonal antibodies can be made to bind to a specific chemical or molecules on a specific cell, not just pathogens.
• A monoclonal antibody has been produced to treat pancreatic cancer. Explain how the monoclonal antibody works to treat pancreatic cancer. (3)

  1. mAb (made that) will only attach to / target (antigen on) cancer cells

  2. mAb is attached to radioactive substance

  3. So radioactive substance will (bind to cancer cells and) stop them growing / diving
• Scientists have produced mAbs to Candida albicans using human lymphocytes produced naturally after infection, instead of using mouse lymphocytes. Describe how mAbs and a fluorescent dye could be used to see Candida albicans pathogens on a microscope slide. (3)

  1. Bind fluorescent dye to mABs
  2. Put bound fluorescent mABs on slide (then rinse off)
  3. mABs will bind to Candida albicans and show up under microscope / UV lamp
• Scientists have used human lymphocytes to make mAbs to some types of cancer cells. Suggest why these new mAbs have been more successful in treating diseases in humans than mAbs made using mice. (1)

  ● Body less likely to reject the mABs

  ● Human lymphocytes have already responded to that infection / cancer cell so they are known to work against the disease
• A virus called RSV causes severe respiratory disease. Describe how injecting a monoclonal antibody for RSV helps to treat a patient suffering with the disease. (2)

  ● mAb is complementary / specific to antigen

  ● mAb binds to antigen on surface of RSV

  ● White blood cells engulf viruses
• To enter a human cell, an antigen on HIV binds with the HIV antigen binding site on the human cell. Suggest how a monoclonal antibody for HIV could help to prevent a person infected with HIV developing AIDS. (3)

  ● mAb is complementary / specific to HIV antigen

  ● mAbs attach to HIV antigens

  ● So HIV cannot bind to human cell
• A pregnancy test strip uses monoclonal antibodies to detect a hormone associated with pregnancy. The stick changes colour if high levels of this hormone are present. Give a reason why this stick would not detect a different hormone. (1)

  ● Antibody is specific for a particular substance / antigen
• Describe how monoclonal antibodies are produced in the laboratory

  1. Inject mouse with specific antigen

  2. Mouse lymphocytes stimulated to make a particular antibody specific to the antigen

  3. Lymphocytes (extracted and) combined with a particular kind of tumour cell to make a cell called

  a hybridoma cell which can...

  ● Divide rapidly (like the tumour cell)

  ● Produce (monoclonal) antibodies (like the lymphocyte)

  4. Single hybridoma cells cloned to produce many identical cells that all produce the same antibody

  5. A large amount of the antibody can be collected and purified
• Ways monoclonal antibodies can be used

  • Diagnosis (e.g. pregnancy tests)
  • Measure levels of hormones and other chemicals in blood
  • Detect pathogens (e.g. HIV)
  • Locate or identify specific molecules in a cell/tissue by binding to them with a fluorescent dye
  • Treat some diseases such as cancer
• Using monoclonal antibodies to treat cancer

  • mAbs made that are specific to/will only bind to antigens present only on cancer cells
  • mAbs attached to a radioactive substance, toxic drug or chemical to stop cancer cells growing and dividing without harming other cells in the body