Heat-shock proteins are a category of proteins which are synthesized under stressful conditions (such as increased temperatures) both by prokaryotic and eukaryotic cells. Heat-shock proteins are a major target of the immune response and thus can be considered dominant antigens. Under physiological circumstances the response to heat-shock proteins is considered to play a role in overall defence against bacterial infections. An aberrant immune response against heat-shock proteins may lead to autoimmunity; adjuvant arthritis in Lewis rats. Current evidence also points towards a role of T cell immunity against heat-shock proteins in the etiology and pathogenesis of human autoimmune diseases such as juvenile chronic arthritis.