Strategies to develop chimerism in vascularized skin allografts across MHC barrier

In this study, we investigated the effects of 7-day-protocols of alphabeta-T-cell receptor monoclonal antibody (alphabeta-TCRmAb), cyclosporine A (CsA), and tacrolimus (FK-506) immunosuppressive monotherapies, and their combinations on the survival of vascularized skin allografts (VSA). Forty-two transplantations of VSA across a strong MHC barrier were performed between ACI (RT1a) donors and Lewis (RT1(l)) recipients in seven groups. Isograft and allograft rejection controls received no treatment. Treatment groups received a 7-day protocol of alphabeta-TCRmAb, CsA, or FK-506 monotherapy, or a combination of alphabeta-TCRmAb/CsA and alphabeta-TCRmAb/FK-506. VSA transplants were evaluated on a daily basis. Donor-specific chimerism was determined by flow cytometry (FC). The combined protocols of alphabeta-TCRmAb/FK-506 and alphabeta-TCRmAb/CsA significantly prolonged VSA survivals compared to monotherapy groups ( P < 0.005). FC analysis revealed 15.82% of donor-specific chimerism on day 7 under the alphabeta-TCRmAb/CsA protocol and a gradual chimerism decline on day 63 posttransplant. The significant extension of VSA survival achieved under 7-day protocols of combined therapies was directly associated with the presence of donor-specific chimerism.