Bistability in autoimmune diseases.

Autoimmune diseases damage host tissue, which, in turn, may trigger a stronger immune response. Systems characterized by such positive feedback loops can display co-existing stable steady states. In a mathematical model of autoimmune disease, one steady state may correspond to the healthy state and another to an autoimmune steady state characterized by widespread tissue damage and immune activation. We show how a triggering event may move the system from the healthy to the autoimmune state and how transient immunosuppressive treatment can move the system back to the healthy state.