The state of having acquired an immunologic memory that says a normal cell membrane is "other", and having forming antibody responses against it. A viral infection or organic chemical (hapten) may have started the response, but surviving healthy cells may have so close a charge pattern (epitope) that acquired immunity keeps on as if the cell was still "other". Any physical stress that causes the target tissue to become inflamed or replicate rapidly to heal can restimulate the auto-immune response.