Induction of tolerance in rodent cardiac allotransplantation using an MHC class I-derived peptide and cyclosporin A

Background. The synthetic peptide corresponding to residues 75-84 of the human major histocompatibility complex class I molecule HLA-B7 (Allotrap 07) has been shown to inhibit differentiation of cytotoxic T lymphocyte precursors. Subsequent treatment of LEW-1A rats with this peptide was associated with a reduction in the level of cytotoxic activity directed to donor alloantigens. This study was undertaken to investigate the effect of Allotrap 07 on rodent heart allograft survival in LEW-1A recipients. Methods. Heart allografts from Lewis rats were heterotopically transplanted into the infrarenal abdominal aorta of ACI recipients. The treatment groups consisted of different regimens of short-term intravenous Allotrap 07 and oral cyclosporin A. All grafts were palpated daily, with rejection defined as the cessation of palpable contractions. Results. Cardiac allografts transplanted from Lewis to ACI rats survived indefinitely after administration of intravenous Allotrap 07 and oral cyclosporin A. Tolerance induction was donor-specific because third-party Brown-Norway, but not Lewis, grafts were rapidly rejected after implantation into ACI recipients. Conclusions. Because donor-specific tolerance persisted long after cessation of peptide administration and did not occur when cyclosporin A was omitted from the immunosuppressive regimen, the mechanism may involve induction of clonal anergy.