Long-term acceptance of fully allogeneic cardiac grafts by cotransplantation of vascularized thymus in miniature swine.
BACKGROUND
We have previously reported the ability of both thymokidney and vascularized thymic lobe (VTL) allografts to induce transplantation tolerance to renal allografts across a full major histocompatibility complex (MHC) mismatch in thymectomized miniature swine. However, whether vascularized thymus is capable of inducing tolerance to less tolerogeneic organs when it is transplanted simultaneously is not yet known. The present study investigates cardiac allograft survival and the mechanism of long-term acceptance in recipient swine following cotransplantation of VTL and cardiac grafts from fully MHC-mismatched donors.


METHODS
Animals received a heart graft, a heart graft and a VTL, or a heart graft and a donor thymocyte infusion. Immunosuppressive regimens consisted of 12 or 28 days of tacrolimus.


RESULTS
All animals that received a VTL maintained their grafts significantly longer than their counterparts that received only a heart graft, and those receiving 28 days of tacrolimus maintained their heart grafts long-term. Recipients of a donor thymocyte infusion demonstrated slightly prolonged cardiac graft survival but all rejected their grafts, highlighting the importance of thymic stroma. Cytotoxic T-lymphocyte responses against third-party antigens by cells from tolerant animals showed restriction by both self and donor MHC, whereas responses of controls were restricted to self MHC only. The presence of donor dendritic cells in the VTL grafts and results of co-culture assays suggest that both central and regulatory mechanisms were involved in achieving long-term acceptance.


CONCLUSIONS
This is the first demonstration of the long-term acceptance of fully MHC-mismatched cardiac allografts in large animals.
Nobori
Shuji
S
Transplantation Biology Research Center, Massachusetts General Hospital, Harvard Medical School, Boston 02129, USA.
Samelson-Jones
Emma
E
Shimizu
Akira
A
Hisashi
Yosuke
Y
Yamamoto
Shin
S
Kamano
Chisako
C
Teranishi
Katsuhito
K
Vagefi
Parsia A
PA
Nuhn
Mathew
M
Okumi
Masayoshi
M
Wong
Banny
B
Houser
Stuart
S
Sachs
David H
DH
Yamada
Kazuhiko
K
D000818:Animals; D001706:Biopsy; D002478:Cells, Cultured; D018920:Coculture Techniques; D006085:Graft Survival / Q000187:drug effects / Q000276:immunology*; D016027:Heart Transplantation / Q000276:immunology*; D006649:Histocompatibility Antigens / Q000276:immunology; D007108:Immune Tolerance; D010641:Phenotype; D017154:Stromal Cells / Q000276:immunology; D013552:Swine; D013556:Swine, Miniature / Q000276:immunology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology; D016559:Tacrolimus / Q000494:pharmacology; D013950:Thymus Gland / Q000098:blood supply* / Q000187:drug effects / Q000276:immunology / Q000637:transplantation*; D013997:Time Factors; D014184:Transplantation, Homologous / Q000276:immunology
D006649:Histocompatibility Antigens; D016559:Tacrolimus