Autoreactive T-cell responses to myeloperoxidase in patients with antineutrophil cytoplasmic antibody-associated vasculitis and in healthy individuals

The aim of this study was to evaluate the characteristics of autoreactive T cells to myeloperoxidase (MPO) in patients with MPO-antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis. Peripheral blood T cells from 15 patients with MPO-ANCA-associated vasculitis and 14 healthy individuals were cultured with three recombinant proteins that together comprised the entire MPO sequence (L, all 112 amino acids (AA) of the light chain; HI, AA 1-227 of the heavy chain; HII, AA 212-467 of the heavy chain), and the antigen-specific T-cell proliferative response was measured by ³H-thymidine incorporation. T-cell responses to MPO-L and HI were both detected in four patients and three healthy donors, and responses to MPO-HII were detected in four patients and seven healthy donors. These findings indicate that at least three independent T-cell epitopes exist on the MPO molecule. Interestingly, the patients whose T cells showed these MPO-induced responses were mainly in remission. Peripheral blood T cells reactive with MPO were primarily of the HLA-DR-restricted CD4⁺ phenotype. In summary, we successfully used recombinant MPO fragments to detect autoreactive CD4⁺ T cells to multiple MPO epitopes in blood samples from patients with MPO-ANCA-associated vasculitis and healthy individuals.