Antibodies

Antibodies

Antibodies
1. Proteins synthesised by B cells
2. When the body is invaded by non-self material, the B cells produce antibodies
3. React with antigens on the surface of the non-self material
  1. Bind to them precisely
  2. Highly specific
4. Each antibody has its own antigen
Antibody structure
1. Made of 4 polypeptide chains
  1. One pair are long, called heavy chains
  2. One pair are shorter, called light chains
2. Change shape by moving as if they have a hinge in the fork of the Y shape
3. Have a binding site
  1. Forms antigen-antibody complexes here
  2. Called the variable region
    1. Different for every antibody
4. Constant region
  1. Same in all antibodies
Monoclonal antibodies
1. A pathogen entering the body is likely to have lots of different antigens on its surface
2. Each antigen will induce a different B cell to multiply and clone itself
3. These clones will each produce a different antibody, collecttively known as polyclonal antibodies
4. Single type of antibody is known as a monoclonal antibody
5. Production
  1. Expose a mouse to non-self material against which an antibody is required
  2. The B cells in thhe mouse produce polyclonal antibodies, which are extracted from the mouses spleen
  3. To enable B cells to divide outside of the body, they are mixed with a cell that divides readily outside of the body
  4. Detergent is added to the mixture to break down the cell-surface membranes of both types of cell, enabling them to fuse together
  5. Fused cells are separated under a microscope and each cell is cultured to form a group. Each clone is tested to see if it is producing the correct antibody
  6. Any clone producing the correct antibody is grown on a large scale and antibdies are extracted from the growth medium
  7. As they are from a mouse, the antibodies have to be modified to make them like human cells - humanisation
Ethical production and use of monoclonal antibodies
1. Involves use of animals
  1. Used to produce both antibodies and tumour cells
  2. Tumour cells - deliberately inducing cancer in animals
  3. Guidelines to minimise suffering, but some still have reservations
2. Iliminate need for humanisation
  1. Transgenic mice can be used
  2. A human gene is placed into the mice
  3. Ethics of genetic engineering
3. Treat diseases
  1. Saving many lives
  2. Some deaths associated with their use in the treatment of multiple sclerosis
4. Testing
  1. In March 2006, 6 healthy volunteers took part in the trial of a new antibody
  2. Within minutes they suffered multiple organ failure
  3. All volunteers survive, but raises issues

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	Created by Beth Ritchie over 10 years ago