T cell epitope expression of mycobacterial and homologous human 65-kilodalton heat shock protein peptides in short term cell lines from patients with Behçet's disease.

T cell epitopes of the 65-kDa heat shock protein (HSP) were mapped in patients with Behçet's disease (BD), by stimulating T cells with the overlapping synthetic peptides derived from the sequences of the Mycobacterium tuberculosis 65-kDa HSP. Significant lymphoproliferative responses were stimulated with four HSP peptides in BD, as compared with the related disease (recurrent oral ulcers), unrelated disease, and healthy controls (p < 0.05 to 0.005). In order to assess the relative frequency of sensitized lymphocytes by these peptides, 7353 short term cell lines were generated from the lymphocytes of patients and controls. Peptides 111-125, 154-172, and 311-325 (p < 0.001) and peptide 219-233 (p < 0.02) yielded significantly greater frequency of STCL in BD than in healthy and disease controls. All but peptide 154-172 stimulated only the CD4+ subset of T cells, although there was no evidence that reactivity to the selected peptides is restricted by DR2 to DR7 Ag. HLA-B51 is significantly associated with BD, but there was no evidence that B51 was a restricting element, when B51+ patients were compared with B51- patients with BD, and with B51+ healthy control subjects. A comparative investigation was then carried out between the corresponding mycobacterial and human HSP peptides. Similar or higher lympho-proliferative responses were stimulated by the human peptides compared with the mycobacterial peptides. These results suggest that the four peptide determinants within the 65-kDa HSP might be involved in the pathogenesis of BD. Whereas the high microbial load and associated stress proteins found in oral ulceration of BD may initiate an immune response to these conserved epitopes, expression of autoreactive T cell clones might be stimulated by immunodominant T cell epitopes of endogenous HSP which may induce immunopathologic changes.