Low Dose Interleukin-2 Induces Exosomes With Tolerance Markers (Pdl1, Cd73) And Significantly Delays Development Of Chronic Rejection Following Murine Heterotopic Cardiac Transplantation

Purpose Aim of the study is to determine the effect of low dose interleukin-2 (IL-2) therapy on the kinetics of induction of circulating exosomes with tolerance markers (PDL1, CD73) and their role in abrogating chronic rejection following murine heterotopic cardiac transplant (HTx). Methods Allogenic (BALB/c to C57BL/6) HTx was performed heterotopically in abdominal cavity. Costimulatory blockade consisting of MR1 (250 μg/ip day 0) and CTLA4-Ig (200 μg/ip day 2) was performed. Low dose IL-2 (2000IU/day) was administered from day 15 post-transplant for 3 weeks. Sera was collected on days 7-100 for kinetic analysis of exosome induction and characterization of PDL1, CD73, cardiac self-antigens (SAgs) (Myosin, Vimentin), class II MHC trans-activator (CIITA), and 20S proteasome by western blot using specific antibodies (Abs) and Abs to SAgs. Results BALB/c to C57BL/6 HTx rejected transplanted heart with median survival time of 8 (7-9) days. HTx done following costimulatory blockade developed chronic rejection with mean survival time 26 (7-47) days. Exosome and Ab development demonstrated induction of exosomes with Vimentin (2.2± 1.0 vs 0.6±0.1; p Conclusion Circulating exosomes containing cardiac SAgs and development of Abs to SAgs lead to chronic rejection in a murine model occurring after costimulation blockade following allogenic HTx. Low dose IL-2 abrogated chronic rejection and induced circulating exosome with tolerance markers. This result supports an important role for exosomes, inducing tolerance and significantly delaying development of chronic rejection in murine model of chronic cardiac allograft rejection.