The Role of Lymph Nodes' Transfer and Lymphangiogenesis In Vascularized Composite Allotransplantation
Ioana Lese Catherine Tsai, Mai Abd El Hafez, Radu Olariu, Adriano Taddeo
Background: The lymphatic system plays an important role in modulating inflammation and autoimmune disease, along with organ immune-rejection processes. The lymph node (LN) is the first site of contact between donor and recipient immune cells, and it has been postulated that this plays an important role in inducing peripheral tolerance after transplantation. However the role of lymphatic reconstitution after vascularized composite allotransplantation (VCA) has not previously been studied. The aim of this study is to assess the impact of regional donor lymph nodes and lymphangiogenesis on graft survival after VCA.
Materials and Methods: A total of 18 Brown-Norway to Lewis rats hind-limb transplantations were performed, with 9 receiving grafts containing popliteal and inguinal lymph nodes (LNs) (Group LN+) and 9 receiving grafts depleted of all LNs (Group LN-). To assess lymphangiogenesis, rats received daily lymphography after injection of Indocyanine Green into the transplant limb starting post-operative day 2. Rejection was evaluated macroscopically and graded from 1 to 3 (most severe). Rats were sacrificed on day of Grade 3 rejection, and blood, LNs, skin, spleen, thymus, and bone marrow were collected to assess donor/recipient lymphocyte composition by flow cytometry.
Results: Survival data was available for 15 rats (7 LN+, 6 LN-). There was a trend towards better graft survival in the LN+ group compared to the LN- group (mean 8.8 vs 8.2 days, respectively). There was a trend towards more overall FOXP3CD25+ regulatory T-cells as well as donor-specific regulatory T-cells in the blood of the LN+ group compared to the LN- group. When lymphangiogenesis was able to be seen, it occurred earlier in the LN+ group compare to the LN- group (3.5 days vs 5 days, respectively).
Conclusion: Hind-limb transplantations with LNs showed increased level of regulatory T cells and chimerism in the recipient. Survival was improved and lymphangeogenesis occurred earlier when transplants included LNs. These results underline the potential of specifically targeting lymphatic vessels and LN to influence VCA rejection.
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