Your immune system is made up of a large network of cells, tissues, and organs. They work together to fight off infections and other harmful substances.
But the immune system doesn’t always work the way it should. Some disorders make the immune system unable to fight off infections. In other disorders, the immune system actually attacks the body’s cells or organs the same way it would attack an infection. This is what happens in autoimmune disorders like lupus and rheumatoid arthritis.