Effect of Mesenchymal Stem Cells on ILT3 Expression in the Splenocytes of Skin Graft Recipient Mice

Background: Mesenchymal stem cells (MSCs) are considered as effective therapeutic cells in transplantation due to their immunomodulatory activities. However, precise mechanism of MSCs immunomodulatory activity is not completely understood. Objectives: To study the role of Immunoglobulin-like transcripts-3 (ILT3) immunomodulatory receptor in immune tolerance induced by MSCs in skin transplantation model and induction of tolerogenic dendritic cells (Tol-DCs) by MSCs through up-regulation of ILT3. Methods: C57BL/6 skin grafts were transplanted to the back of BALB/c mice. Recipient mice received MSCs on days 0, 1 and 2 post transplantation. On days 2, 5 and 10 post skin transplantation, ILT3 and forkhead box P3 (FOXP3) expression in the spleens of MSCs treated mice were evaluated. Furthermore, MSCs and DCs were co-cultured in cell culture plates and transwell systems. Then, the expressions of ILT3 mRNA and protein in MSC-treated DCs were evaluated. Additionally, MSC-treated DCs were co-cultured with allogeneic T-cells and FOXP3 expression in T-cells was evaluated. Results: The expression of ILT3 and FOXP3 were higher in the splenocytes of MSCs-treated mice early post-transplantation. Furthermore, we observed that MSC-treated DCs can increase FOXP3 expression in Tcells. But, we could not find any differences in ILT3 expression between MSC-treated DCs and untreated ones. Conclusion: One of the mechanisms underlying MSCs immunomodulatory function could be up-regulating ILT3 expression in splenocytes. But our results did not support the hypothesis that MSCs induce Tolergenic DCs by upregulation of ILT3.