Toxins

TOXINS

  • Toxins are of two types, exotoxin and endotoxin. Exotoxins are toxic proteins secreted by living microorganisms.

Exotoxins

  • Exotoxins can be divided based on site of action and the cell type affected.
  • Neurotoxins – tetanus toxins, enterotoxin – Vibrio cholera. Diphtheria toxin kills several types of cells and hence termed cytotoxin.
  • Some cytotoxins kill leukocytes and hence called leukocidins. Those which lyse the erythrocytes are called hemolysins.
  • Formaldehyde treatment of exotoxins causes inactivation of the toxigenicity without affecting the antigenicity.
  • The formaldehyde treated toxin is called toxoid. It induces antitoxins which react with toxins and neutralize them.Eg: tetanus and diphtheria toxoids.

Endotoxins

  • The lipopolysaccharides of the Gram negative bacterial cell released in to the medium cause the toxic effect. This is due to the lysis of cells which occurs during late growth stages of culture.
  • All endotoxins exhibit similar pharmacological effects. They cause pyrexia, blood changes and shock. Pyrogenicity is the ability to change body temperature  - fever response.
Last modified: Monday, 20 September 2010, 11:26 AM