Antibodies are produced by the B-lymphocytes, they are made up of proteins. They are produced as a result of foreign matter found within the body. Antibodies bind to the complimentary antigens found on the cell surface membranes of a non-self cell.
Antibodies are made up of four polypeptide chains, the chains of one pair are long and are called heavy chains. The other chain is smaller and are called the antigen-antibody complex. The binding site is different on different antibodies and is therefore called the variable region.
Each Binding site consist of a sequence of amino acids that form a specific 3D shape that binds directly to a specific antigen. The rest of the antibody is a constant region, this binds to the receptors on sells such as B-cells. The light chain is attached to the heavy chain by a disulphide bond.
Antibodies are polyclonal as they are clones of one another derived from the source cell, the B-lymphocytes
- Each bacterium will have many different antigens
- Each antigen also produces B-cells to produce different antibodies
- The B-cells also produce clones which produces these different antibodies
- They are polyclonal antibodies
- If a single type of antibody is produced outside the body, they are called monoclonal antibodies
Producing Monoclonal Antibodies
- A mouse is exposed to the non-self material against which an antibody is required
- The B-cells in the mouse then produce a mixture of antibodies, which are extracted from the spleen of the mouse
- To enable these B-cells to divide outside the body detergent is added to the mixture to break down the cell-surface membranes of both types of cells and enables them to fuse together. The fused cells are called hybridoma cells
- The hybridoma cells are separated under a microscope and each single cell is cultured to form a clone
- Any clone producing the required antibody is grown on a large scale and the antibodies are extracted from the growth medium
- Because these antibodies come from a clone formed from a single B-cell, they are called monoclonal antibodies
- As they are produced by mice they need to be humanised.
Uses of Monoclonal Antibodies
- Pregnancy Testing
- Cancer treatments
- Crohn’s disease
- Multiple sclerosis
Monoclonal Antibodies and Cancer
Monoclonal antibodies can be bind with chemo-toxins. In binding to cancer cells, they can administrate the toxin to it, and therefore damage it. The advantage to this method is it only harms the cancer tissues and not healthy cells.