This figure shows that exotoxins are secreted by bacterial cells, Clostridium botulinum for example, and are toxic to somatic cells. Somatic cells have antibodies on the cell surface to target exotoxins and bind to them, preventing the invasion of somatic cells. The binding of the exotoxin and antibody forms an antigen-antibody interaction and the exotoxins are targeted for destruction by the immune system. If this interaction does not happen, the exotoxins bind to the exotoxin receptors that are on the cell surface and causes death of the host cell by inhibiting protein synthesis. This figure also shows that the application of heat or chemicals to exotoxins can result in the deactivation of exotoxins. The deactivated exotoxins are called toxoids and they are not harmful to somatic cells.