Antibodies to heat shock proteins in patients with pulmonary sarcoidosis

Serum concentrations of IgG, IgA, and IgM antibodies to three heat shock proteins (HSPs)--ubiquitin, HSP70, and HSP90--were measured using ELISA in 37 patients with pulmonary sarcoidosis. When compared to healthy controls (n = 44), increased concentrations of IgA and IgG antibodies to ubiquitin were found in 13 (35.1%, p < 0.002) and 7 (18.9%, p < 0.05) patients, respectively. In 10 patients (27.0%) elevated concentrations of IgG antibodies to HSP70 were detected (p < 0.02), whereas IgA antibodies to this protein were found in 7 cases (18.9%, p < 0.05). IgM antibodies to ubiquitin and HSP70, and antibodies to HSP90 were not detected in patients' sera. The levels of antibodies to ubiquitin and HSP70 correlated well with each other within the given immunoglobulin class (r = 0.7391, p < 1E-5 and r = 0.9854, p < 1E-5 for IgG and IgA class, respectively). There was also a weak correlation between the level of IgG antibodies to HSP70 and both serum activity of angiotensin converting enzyme (SACE; r = 0.4668, p < 0.005) and serum level of soluble receptor for interleukin 2 (sIL-2-R; r = 0.4142), p < 0.02). A similar tendency was seen with IgG antibodies to ubiquitin. Furthermore, there was an association between the increased concentration of C-reactive protein (CRP) and increased levels of IgG antibodies to ubiquitin and HSP70 (p < 0.005 and p < 0.05, respectively). Our results suggest that antibodies to various HSPs are present in a subset of patients with sarcoidosis. The humoral immune response to HSPs relates probably to the immune activation and/or infection.