Identification of human heat shock protein 60 (Hsp60) and anti-Hsp60 antibodies in the peripheral circulation of normal individuals

Although primarily regarded as being intracellular, this study has identifi ed the presence of heat shock protein 60 (Hsp60) in the peripheral circulat ion of normal individuals. The median Hsp60 concentration was approximately 3.5-fold higher in females than in males and significantly higher levels o f anti-human Hsp60 antibodies were also detected in females. There were no differences in the levels of antibodies to mycobacterial Hsp60 between male s and females, nor did antibody levels correlate with Hsp60 concentrations. Hsp60 was not released from mitogenically stimulated peripheral blood mono nuclear cells. The potential physiological roles for circulating Hsp60 are unknown. Given the emerging evidence that inappropriate reactivity to heat shock proteins is involved in autoimmune disease and that T cells responsiv e to self Hsp60 appear to be protective, these findings suggest that circul ating Hsp60 may be involved in the regulation of tolerance to self and immu nity to bacterial forms of these widely expressed and structurally conserve d proteins.