Because the components that make up our immune system are involved in the pathologies of so many diseases and even biomechanical disorders, a simple description of the basic functions of this system may help with understanding how diseases as diverse as radiation sickness, arthritis, influenza or Aids can be mediated if the immune system is robust.
Our resistance to pathogenic microorganisms including bacteria and viruses is a highly complex system involving a range of defense mechanisms. The first line of defense is our skin which provides a physical barrier. However, this is not a complete barrier since there are orifices in our body and possibly wounds through which microorganisms can penetrate. We have several other lines of defense, for example physically ejecting the microorganisms by sneezing and coughing or entrapping them in mucus linings of our body tissues. We also have chemical mechanisms in which the microorganisms are broken down with enzymes, or the acid environment of the stomach that kills them off.
Unfortunately, despite these basic resistance mechanisms we are still prone to a multitude of disease causing microbes (pathogens) and this is where our immune system comes into play. Once the pathogens get through the initial barriers it is up to our body’s components of the immune system to eliminate them or prevent them from functioning.