Antibodies defend the body against bacterial, viral, and other invaders. But sometimes the body makes antibodies that attack healthy cells. In these cases, autoimmune disorders develop. Immune abnormalities in patients with psychosis have been recognized for over a century, but it has been only relatively recently that scientists have identified specific immune mechanisms that seem to directly produce symptoms of psychosis, including hallucinations and delusions. In other words, some forms of psychoses might just be an autoimmune disorder.