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Achieving Allograft Protection through Co-implantation with Donor Antigen-primed Lymph Node Stromal Cells
Location: 47
Mentor: Dr. Alice Tomei
Objective/Background: Pancreatic islet transplantation requires lifelong immunosuppression, reducing its applicability. We aim to eliminate the need for immunosuppression by co-transplanting fibroblastic reticular cells (FRCs), a lymph node stromal cell subtype. FRCs are unconventional antigen-presenting cells that contribute to restraining autoreactive T cells and could be used in transplantation to prevent alloreactive T cell activation. We hypothesize that autologous FRCs co-transplanted with allogeneic donor islets can uptake alloantigen and reprogram the recipient’s alloimmune response toward inactivation/anergy.
Methods: In all experiments, recipient-matched C57BL/6 FRCs were pre-conditioned with or without 10ng/mL interferon-γ (IFNγ) for 72h. FRCs were incubated with CellTrace-labeled NIT1 (fully mismatched to B6) cell lysate or 50µM chicken ovalbumin257-264 (SIINFEKL) peptide overnight. For kinetics, cells were cultured in regular media after overnight treatment. Flow cytometry was used to detect labeled lysate uptake and anti-SIINFEKL-H2Kb for antigen presentation. SIINFEKL antigen-primed FRCs and SIINFEKL-reactive cells were co-cultured overnight while cell activation was measured via β-galactosidase. Data was analyzed by two-way ANOVA.
Results: Uptake of fluorescent NIT1 lysate was dose-dependent, and 96.3±2.6% of FRCs took up lysate at high dose. Confocal microscopy demonstrated donor antigen localization within lysosomes. Donor antigen was cleared from FRCs by 72h. IFNγ potentiates SIINFEKL presentation and 99.9±0.1% of IFNγ-treated FRCs presented SIINFEKL. SIIFNEKL-reactive cells were activated by antigen-primed FRCs independent of IFNγ treatment.
Conclusion: In vitro, FRCs can acquire exogenous antigen, present in MHC I, and activate SIINFEKL-reactive cells. These results predict that FRCs can uptake allogeneic donor cell antigen and can present to alloreactive recipient T cells in in vivo co-transplantation.
