Low levels of heat shock proteins-60 and -65 autoantibodies in Sjögren's syndrome

Background: Heat shock proteins are highly conserved immunodominant antigens found in various species. Humoral immune responses to mycobacterial HSP65 and human HSP60 have been established in a number of human autoimmune diseases. Objective: To assess the prevalence of antibodies to HSP60 kDa and HSP65 kDa in patients with Sjögren's syndrome as compared to normal subjects. Methods: Thirty-seven patients with SS were compared with normal controls. The antibodies against human HSP60 were measured by the Anti-Human (IgG/IgM) HSP60 ELISA kit. IgGs and IgMs to mycobacterial HSP65 were determined using an enzyme-linked immunosorbent assay with mycobacterial recombinant HSP65 antigens. Results: The levels of both anti-HSP60 and -HSP65 were lower in patients compared with controls. IgG autoantibodies to HSP60 were significantly different between groups: 162 ± 55.1 ng/ml in controls versus 112.3 ± 30.6 ng/ml in SS patients (P < 0.001). The levels among controls of anti-HSP65 IgM isotype were also significantly higher than among the SS patients: 111.6 ± 33.4 U/ml versus 96.1 ± 8.9 U/ml (P= 0.01). Conclusions: The results of the present study show that the levels of different isotypes of anti-HSP60 and HSP65 antibodies were lower in patients with SS than in normal subjects. Additional studies in larger patient populations are required to evaluate the prevalence of these autoantibodies in SS patients.