The PD-1: PD-L1 is a potent inhibitory pathway involved in immune regulation and a potential therapeutic target in transplantation. In this study, we show that overexpression of PD-1 (PD-1 Tg) on T cells promotes allograft tolerance in a fully MHC-mismatched cardiac transplant model when combined with costimulation blockade (CTLA-4-Ig). PD-1 overexpression on T cells also protected against chronic rejection in a single MHC II mismatched cardiac transplant model, while it still allowed the generation of an effective immune response against an Influenza A virus. Notably, Treg cells from PD-1 Tg mice were required for tolerance induction and presented higher ICOS expression than those from wild-type mice. Survival benefit of PD-1 Tg recipients required ICOS signaling and donor PD-L1 expression. These results indicate that modulation of PD-1 expression, in combination with a costimulation blockade, is a promising therapeutic target to promote transplant tolerance.
Thiago J. Borges, Naoka Murakami, Isadora T. Lape, Rodrigo B. Gassen, Kaifeng Liu, Songjie Cai, Joe Daccache, Kassem Safa, Tetsunosuke Shimizu, Shunsuke Ohori, Alison M. Paterson, Paolo Cravedi, Jamil Azzi, Peter Sage, Arlene Sharpe, Xian C. Li, Leonardo V. Riella