Usually, your immune system defends your body from many of the things that can harm it. But when the system doesn't work right, it can attack healthy tissues and organs. One part of your immune system is a protein called tumor necrosis factor, also known as TNF, which is produced naturally by the body's immune system. But in certain immune diseases, some people produce too much TNF. This often leads to inflammation. HUMIRA is a medication called a TNF blocker. It works by binding to TNF molecules and blocking them. This helps reduce the inflammation that can lead to symptoms of Crohn’s disease or ulcerative colitis.