Monoclonal Antibodies

• Antibodies aren't only for the immune system - scientists have engineered them for lots of new uses
• Monoclonal antibodies are identical antibodies
• Antibodies are produced by B-lymphocytes - a type of white blood cell
• Monoclonal antibodies are produced from lots of clones of a single white blood cell. This means all the antibodies are identical and will only target one specific protein antigen. However, you can't just grab the lymphocyte and that made the antibody and grow more - lymphocytes don't divide easily
• Tumour cells, on the other hand, don't produce antibodies but divide lots - so they can be grown really easily
• It's possible to fuse a mouse B-lymphocyte with a tumour cell to create a cell called a hybridoma
• Hybridoma cells can be cloned to get lots of identical cells. These cells all produce the same antibodies (monoclonal antibodies). The antibodies can be collected and purified
• You can make monoclonal antibodies that bind to anything you want, e.g. an antigen that's only found on the surface of one type of cell. Monoclonal antibodies are really useful because they will only bind to (target) this molecule - this means you can use them to target a specific cell or chemical in the body

  
• Monoclonal antibodies are used in pregnancy tests
• A hormone called HCG is found in the urine of women only when they're pregnant. Pregnancy testing sticks detect this hormone
• How pregnancy tests work

  • The bit of the stick you wee on has some antibodies to the hormone
  • If the test strip has some more antibodies to the hormone stuck onto it (so that they can't move)

  
• How pregnancy tests work

  If you're pregnant and you wee on the stick:

  • The hormone binds to the antibodies
  • The urine moves up the stick, carrying the hormone
  • The hormones binds to the antibodies on the strip
  • So the hormone gets stuck on the strip turning it blue

  
• How pregnancy tests work

  If you're not pregnant and you wee on the stick:

  • The urin still moves up the stick, carrying the antibodies. But there's nothing to stick to the antibodies onto the test strip so it doesn't go blue
• Monoclonal antibodies can be used to treat diseases
• Different cells in the body have different antigens on their cell surface. So you can make monoclonal antibodies that will bind to specific cells in the body
• Cancer cells have antigens on their cell membranes that aren't found on normal body cells. They're called tumour markers
• In the lab, you can make monoclonal antibodies that will bind to tumour markers
• An anti-cancer drug can be attached to monoclonal antibodies. This might be a radioactive substance, a toxic drug or a chemical which stops cancer cells growing and dividing
• The antibodies are given to the patient through a drip. The antibodies target specific cells (cancer cells) because they only bind to the tumour markers. The drug kills the cancer cells but doesn't kill any normal body cells near the tumour

  
• Monoclonal antibodies can be used to:

  • Bind to hormones and other chemicals in blood to measure their levels
  • Test blood samples in laboratories for certain pathogens
  • Locate specific molecules on a cells or in a tissue
• Monoclonal antibodies can be used to locate specific molecules on a cell or in a tissue:

  • First, monoclonal antibodies are made that will bind to the specific molecules you're looking for
  • The antibodies are then bound to flourescent dye
  • If the molecules are present in the sample being analysed, the monoclonal antibodies will attach to them, and they can be detected using the dye
• There are some obvious advantages of monoclonal antibodies. One big one is in cancer treatment
• Other cancer treatments that don't involve monoclonal antibodies (e.g. chemotherapy and radiotherapy) can affect normal body cells as well as killing cancer cells, whereas monoclonal antibodies target specific cells
• As monoclonal antibodies target specific cells and don't kill other body cells, this means the side effects of an antibody-based drug are lower than for standard chemotherapy or radiotherapy
• Monoclonal antibodies do cause more side effects than were originally expected, e.g. they can cause fever, vomiting and low blood pressure
• When monoclonal antibodies where first developed, scientists thought that because they targeted a very specific cell or molecule they wouldn't create a lot of side effects. This means that they're not as widely used as treatments as scientists had originally thought they might be