Systemic autoimmune diseases can be induced experimentally in rodents by graft-versus-host or host-versus-graft reactions and by chemicals such as HgCl2, gold salts and D-penicillamine. These models share several features, such as productions of anti-nuclear antibodies, immune glomerulonephritis, MHC class II hyperexpression on B cells, hyper-IgE, increased IL-4 activity and impairment of IL-2 production. This profile of cytokines suggests a central role for TH2-type cells in their pathogenesis. Here, Michel Goldman and colleagues review the data supporting this hypothesis and discuss the possible molecular bases for T-cell activation in chemically-induced systemic autoimmunity.