The invention provides a method of detecting autoimmune disease in a mammal, comprising providing a biological sample from a mammal and detecting proteasome activity, wherein a reduction in proteasome activity from a basal state is indicative of autoimmune disease. In addition, the invention encompasses a method of treating an autoimmune disease in a mammal, comprising administering to a mammal suspected of suffering from an autoimmune disease an agent which restores NF&kgr;B activity in an amount and for a time sufficient to result in normal NF&kgr;B activity in the mammal.