Hodgson, RussellChristiansen, DaleZiolkowski, AndrewMouhtouris, EffieSimeonovic, CharmaineIerino, FrancescoSandrin, Mauro2015-12-100041-1337http://hdl.handle.net/1885/68968Background: Blockade of the inducible costimulator (ICOS) pathway has been shown to prolong allograft survival; however, its utility in xenotransplantation is unknown. We hypothesize that local expression of ICOS-Ig by the xenograft will suppress the T-cell response resulting in significant prolonged graft survival. METHODS.: Pig iliac artery endothelial cells (PIEC) secreting ICOS-Ig were generated and examined for the following: (1) inhibition of allogeneic and xenogeneic proliferation of primed T cells in vitro and (2) prolongation of xenograft survival in vivo. Grafts were examined for Tregs by flow cytometry and cytokine levels determined by quantitative reverse-transcriptase polymerase chain reaction. Results: Soluble ICOS-Ig markedly decreased allogeneic and xenogeneic primed T-cell proliferation in a dose-dependent manner. PIEC-ICOS-Ig grafts were significantly prolonged compared with wild-type grafts (median survival, 34 and 12 days, respectively) with 20% of PIEC-ICOS-Ig grafts surviving more than 170 days. Histological examination showed a perigraft cellular accumulation of Forkhead box P3 (Foxp3) cells in the PIEC-ICOS-Ig grafts, these were also shown to be CD3+CD4+CD25+. Survival of wild-type PIEC grafts in a recipient simultaneously transplanted with PIEC-ICOS-Ig were also prolonged, with a similar accumulation of Foxp3 cells at the periphery of the graft demonstrating ICOS-Ig induces systemic graft prolongation. However, this prolongation was specific for the priming xenograft. Intragraft cytokine analysis showed an increase in interleukin-10 levels, suggesting a potential role in induction/function of CD4+CD25+Foxp3+ cells. Conclusions: This study demonstrates prolonged xenograft survival by local expression of ICOS-Ig, we propose that the accumulation of CD4+CD25+Foxp3+ cells at the periphery of the graft and secretion of interleukin-10 is responsible for this novel observation.Keywords: CD28 antigen; complementary DNA; cytotoxic T lymphocyte antigen 4; immunoglobulin; immunoglobulin Fc fragment; inducible costimulator; interleukin 10; transcription factor FOXP3; unclassified drug; animal cell; animal experiment; animal model; article; CD Foxp3; ICOS-Ig; Treg; Xenotransplantation201110.1097/TP.0b013e31821774e02016-02-24