Objective: To determine a peptide that reacts with cytotoxic T cells (CTL) of patients with paraneoplastic cerebellar degeneration and anti-Yo antibodies with either HLA A24 or B27 supertype. Method: We studied CTL activity of four patients, three were HLA A24-positive and one did not have HLA A24 but had B27 supertype. After an incubation of mononuclear cells with or without peptide and IL-2, CD8-rich fraction was prepared by treatment with Magnetic Cell Sorting system (MACS) twice. CTL activity was calculated by 51Cr release from transfectant, C1RA* 2402 as target cells. The peptide-binding assay was examined by flow cytometry. Results: Two of three HLA A 24-positive patients demonstrated CTL activity against the Yo peptide, AYRARALEL. CTL activity was found to be 19.5% and 11.7% at the effector/target (E/T) ratio of 23:1 and 11:1, respectively. A patient who did not have HLA A24 but had A2 and B27 supertype possessed a CTL activity of 19.4% with 15:1 as E/T ratio. The peptide could bind to HLA A* 2402 molecules but not to A* 0201. Conclusions: We showed CTL activity in two of three Japanese patients with HLA A24 by using HLA A* 2402 transfectant cells as the target. In addition, we identified the first Japanese patient who had B27 supertype, and suggested that the same peptide, AYRARALEL, could be recognized by CTL in this patient.
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