Exogenous IL-10 induces corneal transplantation immune tolerance by a mechanism associated with the altered Th1/Th2 cytokine ratio and the increased expression of TGF-β

The aim of the present study was to examine the effect of exogenous IL-10 transfected rat dendritic cells (DCs) in corneal allografts. Rat lymphocyte separation medium and a cytokine induction method was used to extract and culture precursor cells of rat bone marrow-derived dendritic cells. A corneal transplant model was established, with Sprague-Dawley (SD) rats as the recipients and Wistar rats as the donors. Flow cytometry (FCM) was used to detect the expression of CD83, which indicates a mature dendritic cell, and a specific cell surface stimulatory molecule CD86. Western blot analysis was used to detect interleukin (IL)-10 protein expression and RT-PCR was used to detect cytokine IL-10, IL-2 and TGF-beta mRNA expression in each group. Compared with the other groups, the survival time of corneal grafts in the IL-10-green fluorescent protein (GFP)-DC group was significantly prolonged and H&E staining demonstrated mild graft edema and inflammatory cell infiltration. There was a high expression of IL-10 and a low expression of the surface antigens, CD83 and CD86, with a lower proliferation of T lymphocytes in the IL-10-GFP-DC group. The expression of IL-10 and TGF-beta in the IL-10-GFP-DC group was higher than that in the other groups, while the expression of IL-2 was lower. The transfection of the IL-10 gene inhibited dendritic cell maturation. IL-10 gene-modified immature dendritic cells (imDC) were able to inhibit corneal allograft rejection and induce immune tolerance to prolong the survival time of the corneal graft. The Th1/Th2 deviation and the high expression of TGF-beta may lead to immune tolerance.