Immune regulatory effect of rapamycin and cyclosporine A on experimental corneal allograft survival

Abstract

Abstract Purpose To analyze the efficiency of low dose systemic treatment with rapamycin (Rapa) alone or in combination with cyclosporin A (CsA) in preventing corneal allograft rejection in a high responder strain combination. Methods A total of 80 C57BL/6 mice received corneal grafts of BALB/c donors. Recipients were treated with CsA 3mg/kg/day or Rapa 0.5mg/kg/day monotherapy or received combined treatment. Intraperitoneal injections were started on the day of surgery and continued for 14 days. In addition, corneal samples were subjected to real time RT‐PCR analysis for cytokine transcription. The frequency of CD4+CD25+Foxp3+ T regulatory cells (Treg) in secondary lymphoid organs were measured by flow cytometry. Memory T cells were estimated by Elispot. Results Monotherapy with Rapa significantly delayed allograft rejection (p=0.03). However, the combination of low dose Rapa and CsA prolonged corneal allografts survival at a significantly higher level (MST=17.1 ± 1.37 days, p=0.000004). Addition of CsA to Rapa resulted in down‐regulation of intragraft CD3, IL‐2, IFN‐γ and IL‐10 transcription (p=0.028, p= 0.027, p=0.028 and p= 0.027 respectively). Rapa alone increased the frequency of CD4+CD25+Foxp3+ Tregs in draining lymph nodes, whereas addition of CsA reduced Tregs. Rapa monotherapy as well as combined treatment prevented development of alloantigen specific IFN‐γ producing memory T cells in spleen. Conclusion Combined treatment with low dose CsA and Rapa resulted in superior graft survival and effectively modulated mRNA expression of inflammation and infiltration markers. Supported by DFG (150/14‐2) and SFB650 TP14