Abstract Advances in our understanding of the mechanisms involved in immune activation and immune tolerance have laid the foundation for the development of new strategies for treating autoimmune diseases. In particular, the dissection of the two-signal process of T-cell activation has identified distinct targets that may provide a means of blocking pathological autoimmune responses without causing sustained blockade of protective immune responses. These strategies have shown great promise in animal models for autoimmune diseases, and they are currently the focus of clinical investigation in several autoimmune diseases of humans.
