So it has always been a precept of immunologists that the immune response only concerns foreign material. When I began in this field forty years ago, almost everyone believed that immunity could be directed exclusively against foreign materials. We found that there are a number of instances in which the immune response is directed to something in the body of the host itself. The host may be an animal or it may be a human patient. That is what we call autoimmunity.
Autoimmunity is nothing more than the immune response directed to the body of the patient.
Let me define a second term for you, autoimmune disease. These two terms do not mean exactly the same thing, and the difference may be important to us as we talk about some of these issues. Now, in defining autoimmune disease that way, I imply that there is autoimmunity without autoimmune disease. In fact, we now know that autoimmunity is not at all uncommon and that it exists in all of us. Every one of us has some degree of autoimmunity naturally, and it does not seem to do us any harm.