Abstract
Heat shock proteins (HSP) have been implicated in autoimmune diseases such as type I diabetes mellitus, systemic lupus erythematosus, and multiple sclerosis, in which T cell proliferative responses or autoantibodies towards endogenous HSP have been detected (Journal of Autoimmunity2003;20:313). HSP70 can function as an endogenous ‘danger’ signal, acting on antigen-presenting cells and critically influencing the decision between induction of tolerance and immunity upon antigen encounter (Millar et al. Nature Medicine2003; 9:1469). We studied T-cell proliferative responses and auto-antibodies to human HSP60, HSP70 and HSP90 proteins in 20 newly diagnosed aplastic anemia patients, peripheral blood was obtained (11 females, 9 males; age average 36.1±19 years). A non-isotopic immunoassay was used for BrdU incorporation into proliferative T cells and ELISA to measure HSP antibody titer. T cell proliferation was measured as the Eu-fluorescence in a time-resolved fluorometer. A positive result was defined as > 2 standard deviations (SD) from the mean of the controls. T-cell responses to HSP70 in the patient group (N=20; mean±SD Eu-fluorescence= 47,129±36,248) were significantly greater than those of the control group (N=18 healthy adult; mean Eu-fluorescence= 23,941±12,996; p=0.01). Fifty percent of the patients showed increased T cell proliferation after HSP70 stimulation compared to 5% in the control group (p=0.03). T-cell responses of the patient group to HSP90 and HSP60 were similar to those of the control group. Twenty percent of patients showed increased T cell proliferation to HSP 60 and HSP 90 stimulation compared to 5% in the control group (p=0.363). HSP antibody (IgG/A/M) seropositivity was 25% to HSP60, 50% to HSP70, and 5% to HSP90 in patients and 8% to HSP60, 0% to HSP70, and 0% to HSP90 in controls. Heightened autoimmunity to HSP70, but not to HSP60 and HSP90, is a feature of acquired aplastic anemia at presentation.
T Cell-Mediated Chronic Inflammatory Diseases Are Candidates for Therapeutic Tolerance Induction with Heat Shock Proteins
