Role of thymus in operational tolerance induction in limb allograft transplant model.
BACKGROUND
In this study, we evaluated the role of host thymus in tolerance induction in composite tissue allografts (CTA) across major histocompatibility complex (MHC) barrier during a 7-day alphabeta- T-cell receptor (TCR)/ cyclosporine A (CsA) protocol.


METHODS
A total of 62 limb allograft transplants were studied. Euthymic (group A) and thymectomized (group B) Lewis recipients (LEW, RT1(1)) received vascularized hind-limb allografts from hybrid Lewis x Brown-Norway (F1), (LBN, RT1(1+n)) donors. Mixed lymphocyte reaction (MLR) and skin grafting assessed donor-specific tolerance in vitro and in vivo, respectively. Flow cytometry determined the efficacy of immunosuppressive protocols and the presence of donor-specific chimerism. Immunocytochemistry revealed the presence of donor-specific cells in the lymphoid organs of recipients.


RESULTS
Isograft transplants survived indefinitely. For thymectomized rats, the median survival time (MST) of limb allograft in non-treated recipients was 7 days; monotherapy with alphabeta-TCR extended MST to 16 days, and CsA therapy extended it to 30 days. Using the alphabeta-TCR/CsA protocol, the MST of allografts was 51 days. For euthymic rats, the MST of limb allograft in non-treated recipients was 7 days; monotherapy with alphabeta-TCR or CsA extended MST to 13 or 22 days, respectively. Treatment with alphabeta-TCR/CsA resulted in indefinite allografts survival (MST=370 days). MLR and skin grafting confirmed donor-specific tolerance in euthymic recipients. Flow cytometry showed stable chimerism in the euthymic rats and transient chimerism in thymectomized limb recipients. Immunoperoxidase staining revealed the persistence of donor-derived cells in the lymphoid tissues of euthymic recipients.


CONCLUSIONS
We found that the presence of thymus was imperative for the induction of donor-specific tolerance in rat hind-limb composite tissue allografts using a alphabeta-TCR/CsA protocol.
Siemionow
Maria
M
Department of Plastic Surgery, The Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA. siemiom@ccf.org
Izycki
Dariusz
D
Ozer
Kagan
K
Ozmen
Selahattin
S
Klimczak
Aleksandra
A
D000818:Animals; D046528:Chimerism; D016572:Cyclosporine / Q000627:therapeutic use; D005434:Flow Cytometry; D006614:Hindlimb / Q000473:pathology / Q000503:physiopathology / Q000637:transplantation*; D007150:Immunohistochemistry; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D007959:Lymphocyte Culture Test, Mixed; D008221:Lymphoid Tissue / Q000737:chemistry / Q000473:pathology / Q000503:physiopathology; D008285:Major Histocompatibility Complex / Q000276:immunology; D008297:Male; D051381:Rats; D011914:Rats, Inbred BN; D011917:Rats, Inbred Lew; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000032:analysis / Q000627:therapeutic use; D015996:Survival Rate; D013934:Thymectomy; D013950:Thymus Gland / Q000276:immunology* / Q000601:surgery; D013997:Time Factors; D023001:Transplantation Tolerance / Q000187:drug effects / Q000276:immunology*; D014184:Transplantation, Homologous / Q000276:immunology* / Q000473:pathology
D007166:Immunosuppressive Agents; D016693:Receptors, Antigen, T-Cell, alpha-beta; D016572:Cyclosporine