Israel Medical Association Journal

Background: Heat shock proteins are highly conserved immunodominant antigens found in various species. Humoral immune responses to mycobacterial HSP65[1] 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 Sjogren's syndrome as compared to normal subjects.

Methods: Thirty-seven patients with SS[2] were compared with normal controls. The antibodies against human HSP60 were measured by the Anti-Human (IgG/IgM) HSP60 ELISA kit. IgGs[3] 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 among 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 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 on larger patient populations are required to evaluate the prevalence of these autoantibodies in SS patients.

The formerly prevalent concept that intact autoantibodies could not penetrate into viable cells has been defeated by a large amount of experimental findings and clinical observations that indicate otherwise. The penetration of autoantibodies into living cells seems to participate in the pathogenesis of diverse autoimmune diseases, but it may also play a physiological role in healthy individuals. Although the fine mechanisms of the phenomenom remain to be elucidated, the potential use of penetrating autoantibodies as vectors to deliver molecules into cells, with diverse therapeutic purposes, has gained growing interest during the last few years.