When the immune system is reactive against something that is normally a part of the tissues of the body we call this "autoimmunity". When this reaction results in destruction of the cells or organs of the body to the point that the person is sick, it is called autoimmune disease. However, work like ours and that of others suggests that there is a very important role for autoimmunity, and a very important difference between it and autoimmune disease. It turns out that killer B cells and other specialized regulatory cells are often involved in autoimmunity as protectors. By being able to recognize self 'antigens' (see definition in earlier post), these cells go to sites in the body that need protecting, and by creating an immune suppressive environment there, are able to stop other cells from attacking the normal tissue. Mice that don't have these autoimmune regulatory cells are at a much higher risk of developing autoimmune disease, which is also something that happens in humans. One way that we hope to treat autoimmune diseases in the future is by boosting up the regulatory B and T lymphocytes, particularly the ones that have the correct self-reactivity that is specific to the disease being treated.