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Abstract 17: Engineering a “Hybrid Thymus” to Promote Transplant Tolerance

Plastic and Reconstructive Surgery - Global Open: April 2016 - Volume 4 - Issue 4S - p 43
doi: 10.1097/01.GOX.0000488949.01538.27
PRS PSRC Podium Proofs 2016

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Sara AlFadil, MD,* Mi-Jeong Kim, PhD,† Marcos Iglesias Lozano, DVM, PhD,* Byoungchol Oh, DVM, PhD,* W.P. Andrew Lee, MD,* Gerald Brandacher, MD,* Thomas Serwold, PhD,* Giorgio Raimondi, PhD*

From the *Johns Hopkins Medical Institute, Baltimore, Md.; and †Joslin Diabetes Center, Boston, Mass.

PURPOSE: Targeting the process of central (thymic) selection of developing T lymphocytes is the key tolerogenic mechanism of bone marrow transplantation-based protocols of transplant tolerance induction. However, they are not amenable to most transplant recipients. Thymic epithelial cells (TECs), a population of stromal cells residing in the thymus, exerts a major contribution to central selection. However, donor TEC do not develop following bone marrow transplantation protocols. Therefore, we propose a new immunomodulatory strategy based on generating a donor-recipient “hybrid thymus,” through donor TEC engraftment, to reengineer the thymic microenvironment and achieve dominant central tolerance.

METHODS: We developed our own protocol for isolating TEC via a combination of negative and positive selection. Purified BALB/c TEC was injected intrathymically into C57BL/6 with or without co-stimulation blockade [cytotoxic T lymphocyte-associated antigen-4 immunoglobulin (CTLA4-Ig)]. Fourteen and 28 days postinjection donor-TEC survival was assessed, and peripheral T cells analyzed for changes in TCR-β Vβ11 expression—a marker of negative selection.

RESULTS: Our optimized purification protocol yields an average 70% TEC purity. As expected, unmanipulated animals promptly rejected TEC. However, CTLA4-Ig co-administration exerted a significant protection. In this latter group, the percentage of Vβ11+ T cells on d24 was significantly lower indicating functional activity of the engrafted donor TEC.

CONCLUSIONS: Our preliminary data show that the thymic engraftment, survival, and function of allogenic TEC can be promoted by CTLA4-Ig. These exciting results indicate that engineering a donor-recipient hybrid thymus is feasible and has the potential to promote a dominant regulation of alloreactivity that could be conducive to transplant tolerance induction.

© 2016 American Society of Plastic Surgeons