Local Delivery of Regulatory T Cells Promotes Corneal Allograft Survival

Background Regulatory T (Treg) cell-based immunotherapies have been studied as potential cell-based modalities for promoting transplant survival. However, the efficacy of local delivery of Treg cells in corneal transplantation has not been fully elucidated. Herein, we investigated the kinetics of migration of subconjunctivally injected Treg cells and their role in promoting corneal allograft survival. Methods GFP(+)CD4(+)CD25(+)Foxp3(+) Treg cells were isolated from draining lymph nodes (DLNs) of GFP transgenic mice and were subconjunctivally injected to corneal allograft recipients. Next, Treg cells, conventional T cells (Tconv) or a combination of both was locally injected to graft recipients, and graft survival was determined by evaluating opacity scores for 10 weeks. Transplanted mice without treatment served as controls. The frequencies of major histocompatibility complex-II(+)CD11b(+) antigen-presenting cells, IFN gamma(+)CD4(+) Th1 cells, and CD45(+) cells in the DLNs and cornea were evaluated at week 2 posttransplantation using flow cytometry. Expressions of IFN gamma, IL-10 and TGF-beta in the grafts were assessed using reverse transcription polymerase chain reaction and enzyme-linked immunosorbent assay. Results GFP(+) Treg cells were detected in the ipsilateral cornea and DLNs of recipients 6 hours after injection. Subconjunctival injection of Treg cells significantly decreased the frequencies of mature antigen-presenting cells in the graft and DLNs, suppressed Th1 frequencies in DLNs, and inhibited CD45(+) cell infiltration to the graft. Finally, locally delivered Treg cells significantly reduced the expression of IFN-gamma, enhanced the levels of IL-10 and TGF-beta in the graft, and promoted long-term allograft survival. Conclusions Our study elucidates the kinetics of migration of locally delivered Treg cells and shows their role in suppressing host immune response against the allograft.