Cultured thymus tissue implantation promotes donor-specific tolerance to allogeneic heart transplants
Jean Kwun, … , Allan D. Kirk, M. Louise Markert
Jean Kwun, … , Allan D. Kirk, M. Louise Markert
Published June 4, 2020; First published April 30, 2020
Citation Information: JCI Insight. 2020;5(11):e129983. https://doi.org/10.1172/jci.insight.129983.
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Research Article Immunology Transplantation

Cultured thymus tissue implantation promotes donor-specific tolerance to allogeneic heart transplants

Abstract

Eighty-six infants born without a thymus have been treated with allogeneic cultured thymus tissue implantation (CTTI). These infants, who lack T cells and are profoundly immunodeficient at birth, after CTTI from an unmatched donor develop T cells similar to those of recipient that are tolerant to both their own major histocompatibility antigens and those of the donor. We tested use of CTTI with the goal of inducing tolerance to unmatched heart transplants in immunocompetent rats. We thymectomized and T cell–depleted Lewis rats. The rats were then given cultured thymus tissue from F1 (Lewis × Dark Agouti ) under the kidney capsule and vascularized Dark Agouti (DA) heart transplants in the abdomen. Cyclosporine was administered for 4 months. The control group did not receive CTTI. Recipients with CTTI showed repopulation of naive and recent thymic emigrant CD4 T cells; controls had none. Recipients of CTTI did not reject DA cardiac allografts. Control animals did not reject DA grafts, due to lack of functional T cells. To confirm donor-specific unresponsiveness, MHC-mismatched Brown Norway (BN) hearts were transplanted 6 months after the initial DA heart transplant. LW rats with LWxDA CTTI rejected the third-party BN hearts (mean survival time 10 days); controls did not. CTTI recipients produced antibody against third-party BN donor but not against the DA thymus donor, demonstrating humoral donor-specific tolerance. Taken together, F1(LWxDA) CTTI given to Lewis rats resulted in specific tolerance to the allogeneic DA MHC expressed in the donor thymus, with resulting long-term survival of DA heart transplants after withdrawal of all immunosuppression.

Authors

Jean Kwun, Jie Li, Clay Rouse, Jae Berm Park, Alton B. Farris, Maragatha Kuchibhatla, Joseph W. Turek, Stuart J. Knechtle, Allan D. Kirk, M. Louise Markert

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Figure 1

T cell reconstruction and functional transplanted thymus tissue in cardiac allograft recipients with CTTI.

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T cell reconstruction and functional transplanted thymus tissue in cardi...
(A) Schematic outline of experimental design to show naive T cell reconstitution, thymopoiesis, and donor-specific tolerance induced by CTTI. All LW rats were thymectomized and T cell depleted via anti-CD5 mAb before heart transplantation and CTTI. CTTI from F1(LWxDA) rats and hearts from DA rats were transplanted into thymectomized LW recipients. CsA was given for 4 months after transplantation via osmotic pump. The third-party BN heart was transplanted into the neck 2 to 3 months after CsA discontinuation. Control rats experienced identical procedures except they did not receive CTTI. (B) Circulating T cell repopulation after T cell depletion and thymus and heart transplantation. All animals showed dramatic reduction of circulating T cells after T cell depletion. Cardiac allograft recipients with CTTI (blue line) showed gradual repopulation of circulating T cells. Animals without CTTI also showed some degree of circulating T cells (red line). However, naive and recent thymic emigrants CD4 and CD8 T cells were significantly increased (P < 0.01) in animals with CTTI, whereas control animals showed neither circulating naive CD4 and CD8 T cells nor RTE CD4 and CD8 T cells. (C) Engrafted cultured thymus tissues under the renal capsule on day 180 in a recipient of cardiac allograft. Histology showed a distinct structure separate from renal tissue (original magnification, ×20). Engrafted cultured thymus tissue (right panel) showed a normal thymus structure (H&E), viable T cells (CD3), T cell proliferation (Ki67), and Hassall body formation (black arrow) with a lacy pattern (cytokeratin) on epithelial cells, confirming the viability of thymus with thymopoiesis (original magnification, ×200). Data are presented as means ± SD; n = 8–9 animals per group; student’s t test, *P < 0.05; **P< 0.01; ***P < 0.001, ****P < 0.0001; NS, not significant (P > 0.05). CTTI, cultured thymus tissue implantation; LW, Lewis; LWxDA, Lewis × Dark Agouti; DA, Dark Agouti; CsA, cyclosporine A; BN, Brown Norway; RTE, recent thymic emigrant.