Specific antigen(s) in sarcoidosis: a link to autoimmunity?

The nature of the activating antigen, however, has been an enigma over decades of sarcoidosis research. The histological similarities between sarcoidosis and tuberculosis, and the usefulness of tuberculin preparations in the Mendel-Mantoux test, led to the search for an antigen-containing extract, and in the middle of the last century, the first “antigen” was isolated from the spleen cells of patients suffering from sarcoidosis, assuming that these cells contain the active principle inducing the disease [2–4]. However, although this preparation induces granuloma in sarcoidosis patients and has been analysed by different methods [5–7], the nature and origin of the active principle could not yet be identified.