Heat-shock proteins and autoimmunity in humans.

T cells and antibodies against self and non-self hsp are present in both patients and healthy controls. T cells responding to hsp65 can be involved in autoimmune diseases, this was demonstrated for two site-specific animal autoimmune diseases: AA in Lewis rats and diabetes (IDDM) in NOD mice. In human ReA there is evidence for a direct stimulation of joint T cells by antigens of the organisms causing the infection which precedes the joint inflammation. The individual antigens of the triggering bacteria still have to be defined, but hsp65 may be of importance since this is one of the molecules recognized by synovial T cells in ReA patients. In RA there are no clear data implicating an infection in the initiation of joint inflammation, but mycobacteria have been suggested to be involved. We have discussed experimental findings which are in favor of, or in contradiction with, a role of mycobacterial antigens--particularly hsp65--in the etiology of RA. T cells recognizing hsp65 and other mycobacterial antigens are present in the joint, but there is no indication for a specific involvement of one or a limited set of (myco)bacterial antigens in the pathogenesis of RA.