The term systemic lupus erythematosus (SLE) was first introduced in the late 19th century, when it became apparent that some people with these characteristic scarring skin diseases also suffered from severe manifestations of the disease in internal organs, most notably the kidneys. At that time, the concept of autoimmunity was not accepted; in particular, the great pioneer of immunology Paul Ehrlich had declared that autoimmunity was not possible, that nature had an aversion to it, an "autotoxic horror". However, in the mid-20th century, several important discoveries overturned this dogma.