Our immune system allows us to defend against harmful agents (virus, bacteria, etc.), letting us remain healthy. However, sometimes our own genetics may alter our immune system, and our body may attack itself. This is what happens with autoimmune diseases.
We have treatments which allow modulating that immune system that has gone berserk, allowing a better stability and decrease the symptoms presenting when those pathology-derived crisis happen, improving the quality of life.
Examples of autoimmune diseases: Rheumatoid Arthritis, Lupus, Multiple Sclerosis, Fibromyalgia.