The immune system is the natural defense of our organism; It is a mechanism that is found in the body of every living being and that is responsible for protecting us from external agents that can cause us harm (Toxins, bacteria, viruses, poisons, etc.).
Maintaining a strong immune system is important precisely for this reason, since if it weakens, the chances of getting sick increase. If you want to know exactly why our immune system fails and why we really get sick, don't miss this oneHOWTO article. Also, we talk about how you can avoid getting sick so easily.