Monoclonal 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, which means all the antibodies are identical and will only target one specific protein antigen
• Lymphocytes produce antibodies but don't divide easily
• Tumour cells don't produce antibodies but divide lots
• You can 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 which all produce the same antibodies (monoclonal antibodies) - these can be collected and purified
• Making monoclonal antibodies:

  1. inject a mouse with the chosen antigen so its B-lymphocytes produce the correct antibodies
  2. fuse the B-lymphocyte with a tumour cell to make a hybridoma
  3. allow it to divide and produce lots of clones that produce the monoclonal antibodies
• You can make monoclonal antibodies that bind to anything you want
• Monoclonal antibodies are useful because they will only bind to the specific molecule, meaning you can use them to target a specific cell or chemical in the body
• HCG is a hormone found in the urine of women only when they're pregnant, and is detected by pregnancy testing sticks
• Pregnancy tests 1

  the bit that you urinate on contains some antibodies to the HCG hormone, with blue beads attached
• Pregnancy tests 2

  the test strip has some antibodies to the HCG hormone stuck onto it (so they can't move)
• Pregnancy tests 3


  if you're pregnant:

  • the hormone binds to the antibodies on the blue beads
  • the urine moves up the stick, carrying the hormone and the beads
  • the beads and hormone bind to the antibodies on the strip
  • the blue beads get stuck on the strip and turn it blue
• Pregnancy tests 4

  if you're not pregnant:

  • the urine still moves up the stick carrying the blue beads
  • there's nothing to stick the blue beads onto the test strip, so it doesn't go blue
• 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 e.g. liver cells
• Cancer cells have antigens on their cell membranes that aren't found on normal body cells, called tumour markers
• In a lab, you can make monoclonal antibodies that will bind to tumour markers
• An anti-cancer drug can be attached to the monoclonal antibodies bound to tumour markers. This could be a radioactive substance, a toxic drug or a chemical which stops cancer cells from growing and dividing
• The antibodies attached to the anti-cancer drug are given to the patient through a drip
• The drug (antibodies + anti-cancer 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 cell or in a tissue
• Using monoclonal antibodies to locate molecules:

  1. monoclonal antibodies are made that will bind to the specific molecule you're looking for
  2. the antibodies are bound to a fluorescent dye
  3. if the molecules are present in the sample you're analysing, the monoclonal antibodies will attach to them and they can be detected using the dye
• Pros of monoclonal antibodies:

  • cancer treatment - doesn't affect normal body cells when killing cancer cells
  • side effects of antibody-based drugs are lower than for standard chemotherapy or radiotherapy
• Cons of monoclonal antibodies:

  • cause more side effects than expected, e.g. fever, vomiting and low blood pressure
  • aren't as widely used as treatments as scientists had originally thought they might be