ARPE-19 and PBMC co-culture study results. (a) OX40L-C + PBMC abrogates the immunosuppressive effect of RPE alone. No difference was observed between OX40L (C- or N- vectors) or GITR ligand. An approximately 20% to 30% reversal of RPE-mediated immunosuppression is seen when stimulated pBMCs were co-cultured with RPE-OX40L vector. (b) A repeat experiment shows that concomitant transfection of both eYFP-C1-OX40L and eYFP-C1-GITRL vectors into RPE cells resulted into an additive reversal of immunosuppression of stimulated pBMCs, when comparing it to either RPE transfected with OX40L-C or GITRL alone. (pBMC unstim, unstimulated peripheral blood mononuclear cells; pBMC stim, stimulated pBMC with anti-CD3 and anti-CD28; RPE, retinal pigment epithelial cells without transfection; OX40L-C, RPE cells transfected with eYFP-C1-OX40L; OX40L-N, RPE cells transfected with eYFP-N1-OX40L; GITRL, RPE cells transfected with eYFP-C1-GITRL).