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Instant C3a generation after intraportal porcine islets xenotransplantation in non-human primate is dependent on alternative complement pathway activation

Hee Jung Kang¹, Haneulnari Lee¹, Jeong-mi Ha¹, Jae-iI Lee², Jun-Seop Shin², Chung-Gyu Park², and Sang-Joon Kim²

¹Department of Laboratory Medicine, Hallym University College of Medicine, Anyang; ²Xenotransplantation Research Center, Seoul National University Hospital, Seoul, Korea

Intraportal transplantation of porcine islets to non-human primate brings about instant blood-mediated inflammatory reaction (IBMIR), leading to early loss of transplanted islets. To understand the mechanism of IBMIR in porcine islet transplantation, we investigated the change of complement system in blood in contact with porcine islets in vivo and in vitro. Purified adult porcine islets were intraportally transplanted into eight streptozotocin-induced diabetic rhesus monkeys, five of which were treated with cobra venom factor (CVF) 24 h before transplantation. The following complement and coagulation activation parameters were monitored during one week after transplantation: C3a, C4a, C4d, factor Bb, thrombin-antithrombin complex (TAT) and D-dimer. Additionally, in vitro C3a generation and C3 deposition on porcine islets after incubation of porcine islets with 20 % AB type fresh human serum were analyzed and inhibitory effects of anti-human factor B monoclonal antibody (alternative pathway inhibitor) and C1 esterase inhibitor (classical pathway inhibitor) were also assessed. The levels of C3a, factor Bb and TAT, not those of C4a, C4d and D-dimer, increased within 15 min after transplantation and then decreased to the basal level within 2 h in non-CVF treated monkeys. CVF treatment ameliorated immediate increase of those parameters after transplantation. Incubation of porcine islets with fresh human serum in vitro induced C3 deposition on islet cells and generated C3a into soluble phase. The use of anti-factor B antibody efficiently reduced C3a generation but not C3 deposition on islets while C1 esterase inhibitor did not show inhibitory effects. Anti-factor B antibody significantly prolonged porcine islet-induced clotting time of recalcified human platelet-rich plasma. These results demonstrate that intraportal transplantation of adult porcine islets induces complement activation in non-human primate recipient, mainly through alternative pathway, which aggravates coagulation abnormalities. The inhibition of alternative complement pathway would be an effective strategy to reduce IBMIR.

This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MEST) (2010-0021930), a grant from the Korea Health 21 R&D Project, Ministry of Health & Welfare, Republic of Korea (Project No.: A040004), and a grant from Hallym University Medical Center Research Fund (01-2010-15).