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The 2003 Annual Meeting of OASYS_NEW |
Not yet assigned to a slot - 12:40 AM
Tolerance to Mhc-Mismatched Limb Allografts in Rats Can Be Achieved without Induction of Long-Term Hematopoietic Macrochimerism
Quatra F1, Romeo OM1, Eimon T2, Baxter-Lowe LA3, Kong D3, Lowemberg D1, Colonna MR4, Stagno D'Alcontres F4, and Buncke HJ1. (1) Microsurgical Laboratory, CPMC - Research Institute, Davies Campus, 45 Castro Street, San Francisco, CA, USA, (2) Department of Pathology, CPMC, 45 Castro Street, San Francisco, CA, USA, (3) Immunogenetics and transplantation laboratory, University of California, San Francisco, Box 0508, San Francisco, CA, USA, (4) Plastic Surgery, University of Messina, Policlinico Universitario, Via Consolare Valeria, Messina, Italy
In a primate allogeneic kidney transplant model, tolerance has been reported using a combination of T-cell depletion and Deoxyspergualin (DSG) without induction of hematopoietic macrochimerism. We used a similar approach in a rat model of experimental limb transplantation showing clinical donor-specific tolerance across a fully mismatched MHC barrier (RT1-1 / RT1-n) with acceptance of donor-skin grafts and rejection of third-party skin grafts. Treatment included an anti-T-lymphocyte monoclonal antibody and a 20-day administration of DSG in the group that showed longest survival. Non-treated controls rejected in 8-10 days. Materials and methods. This report focuses on the mechanisms of tolerance as investigated by means of flow cytometry, histology and immunohistochemistry. Leucocytes from whole blood and lymphatic organs were labeled with a T-cell marker (anti-TcR) and a donor-specific marker (RT1-Ac). Frozen sections of lymphatic organs and bone marrow were stained with similar biotinylated, fluorescent antibodies. Paraffin-embedded sections of the transplanted limb, lymphatic organs and organs that are specific targets of GVHD were stained with standard hematoxylin-eosin. Results. Microchimerism (<1% of donor-derived mononuclear leukocytes) was detected in the peripheral blood of all animals. Fluorescence above background was found in the spleen, thymus and bone marrow, suggesting the presence of donor- derived cells. Fluorescence pattern in the transplanted limb was different than in the control donor limb. Histology showed absence of rejection. Conclusions. Tolerance to MHC-mismatched limb allografts can be achieved in rats without myeloablative treatment, irradiation or bone marrow infusion, using a T-cell depleting agent and a low-toxicity 20-day administration of DSG making this treatment promising for clinical application. Macrochimerism is not present at 80 days in the peripheral blood. Donor-derived cells are present in the thymus and spleen, suggesting that these organs may contribute to the maintenance of tolerance.