A better understanding of the molecules involved in immune responses has identified many potential targets for the treatment of autoimmune diseases. But although successful therapies have been found for immune disorders in animal studies, few have passed the much harder test of treating human diseases. So far, non-antigen-specific approaches, such as the blocking of tumour-necrosis factor, are achieving some success but the same is not true for antigen-specific approaches. Future therapies will probably include both non-antigen-specific strategies that target cytokines (cell–cell signalling molecules) or block the molecules that stimulate immune responses, and antigen-specific therapies that induce tolerance to self antigens.