Pharmacological preconditioning with adenosine A receptor agonist induces immunosuppression and improves graft survival in novel allogeneic transplantation models.

Adenosine is widely known as a potent modulator of innate and acquired immunity. It is released during transplants, and acts on four subtype receptors. In previous studies, we demonstrated that pharmacological preconditioning (PPC), pre-administration of the selective A receptor (AR) agonist led to AR desensitization, is followed by upregulation of the adenosine A receptor. This immunosuppressive effect resulted in lymphopenia, and it reduced T-cell reactivity. The aim of the current study was to challenge the immunosuppressive effects of AR-PPC in models of allogeneic grafts. PPC mice were treated by intraperitoneal injection using specific adenosine AR agonist 24 h and 12 h before starting any procedure. We challenged our method in novel allogeneic muscle and skin grafts models. Mice and grafts were assessed by complete blood counts, MLR from PPC splenocytes, and pathological evaluation. We found a significant reduction in WBC and lymphocyte counts in PPC-treated mice. Two-way MLR with splenocytes from PPC grafted mice showed decreased proliferation and anergy. Histology of PPC allogeneic grafts revealed profoundly less infiltration and even less muscle necrosis compared to vehicle treated allografts. Similar results observed in PPC skin transplantation. To conclude, PPC moderated graft rejection in separate allogeneic challenges, and reduced lymphocytes infiltration and ischemic damage.