Immune system; your personal army
The cells of your immune system are standing guard 24/7 as the soldiers of your own personal army throughout your body. The moment something goes wrong in your intestines, your immune system will take action. Your immune cells will also keep watch over your intestines to make sure no intruders will enter. The moment a pathogen is spotted, your immune system will do everything to fight the intruder.
Bullet casings at the crime scene
The reaction of the immune system is measurable. Usually, it is about particles of substances which the immune system uses. It is almost like searching for bullet casings at the scene of the crime.
In the laboratory we can measure the reaction of the immune system, by doing this we can find the source of the inflammation. Furthermore, we can measure how intense the inflammation is and most important: the possible causation!