The transporter that translocates ergothioneine has been identified. Described are methods for identifying and obtaining compounds capable of modulating ergothioneine transport as well as the use of such compounds for the treatment of diseases ergothioneine may be involved in such as autoimmune diseases, in particular rheumatoid arthritis, as well as other diseases arising from cell damage caused by radiation, radicals and relative oxidant species. Furthermore, diagnostic means and methods for determining the presence or susceptibility to such a disease are provided.
