Influence of Cold Ischemia Time, Pretransplant Anti-Porcine Antibodies, and Donor/Recipient Size Matching on Hyperacute Graft Rejection After Discordant Porcine to Cynomolgus Kidney Transplantation

Abstract

Organs transplanted between phylogenetically disparate species, such as from the pig into the primate, are subject to hyperacute rejection (HAR). This form of xenograft rejection is mediated by preformed natural antibodies and is believed to occur invariably in discordant xenografts thus leading to rapid destruction and complete thrombosis of the graft. Recent data, however, have shown that in the porcine to cynomolgus monkey setting, HAR is not inevitably seen after porcine kidney transplantation. The influence of preoperative antiporcine antibody levels in the recipient, cold ischemia time, and donor organ weight on the onset of HAR was investigated by using unmodified large white pigs (aged 3-12 weeks) as organ donors and adult cynomolgus monkeys (aged 1.5-3.5 years) as recipients. Porcine kidney xenotransplantation was performed in either a non-life-supporting model (n=7) or in a life-supporting model (n=8). In both models, no correlation was found between cold ischemia time and HAR. When preoperative anti-porcine antibody levels were investigated, a significant increase in incidence of HAR was observed in animals with elevated anti-porcine IgM (P<0.05) but not IgG levels (P=NS). Interestingly, although 5 of 12 grafts with an organ weight of less than 50 g underwent HAR, none of three grafts with a donor organ weight of more than 70 g showed signs of HAR. In addition, all three larger grafts showed intraoperative and postoperative urine production, although only in 1 (48 g) of the 12 grafts weighing less than 50 g primary graft function was observed. In one animal, a second porcine kidney (23 g) was successfully transplanted (without HAR) immediately after HAR and subsequent removal of a first porcine kidney (20 g). These results indicate that in the porcine to cynomolgus monkey setting anti-porcine IgM rather than IgG anti-porcine antibody levels seem to be of predominant importance for the induction of HAR. By increasing the donor organ size and weight the frequency of the onset of HAR can be at least reduced. This is most likely due to immunoabsorption of the recipients preformed antibodies in the porcine kidney without lethal damage for the graft.

Acute vascular rejection is associated with systemic complement activation ina pig‐to‐primate kidney xenograft model

“…As shown in this study (Fig. 1) and by others (E. Cozzi, personal communication), the analysis of the recipient's serum anti‐porcine antibodies by either hemolytic assays on porcine red blood cells [3] or by non‐specific FACS analysis of antibody binding on PBL [7], reveals significant changes in recipient antibody titer only in a subset of episodes of xenograft rejection. Therefore, measurement of plasma C3a or sC5b‐9 levels could be used as an additional marker for early immunologically mediated damage of the xenograft.…”

“…The reason for the absence of alterations in systemic anti‐porcine antibody levels during the majority of episodes of AVR might be the trapping of the antibodies in the xenograft itself. This hypothesis is supported by the fact that in a non‐life‐supporting model of discordant pig‐to‐cynomolgus xenotransplantation established in our laboratory [7] as well as in a model of heterotopic cardiac transplantation without post‐operative immunosuppression [20] an increase in anti‐porcine antibody levels was in fact observed but only after surgical removal of the xenograft. As long as the graft was perfused in situ, no significant changes in antibody levels were described.…”

“…Kidneys were harvested from anesthesized pigs using a standard technique [7]. After canulation of the infrarenal aorta both kidneys were removed following systemic heparinization and consecutive transaortal hypothermic perfusion with HTK preservation solution (HTK, Köhler‐Chemie GmbH, Alsbach‐Höhnlein, Germany).…”

“…Bound cynomolgus antibody was detected with goat anti‐human FITC secondary antibodies detecting IgG (Dianova, Hamburg, Germany) or IgM (Dian‐ova, Hamburg, Germany), respectively. These antibodies are known to cross‐react with cynomolgus immunoglobulins [7]. The antibodies had been pre‐absorbed using porcine serum.…”

Appropriate Donor Size for Porcine Liver Xenotransplant

“…On the other hand, the ability to estimate and select an organ which is proper in size and weight before transplant may have advantages, such as enhancement of survival and function of the xenograft, 31 as well as a lower incidence of hyperacute rejection. 32 In this study, the mean of total liver weight was 696.6 ± 91.3 g. The percentage of whole liver weight to body weight was approximately 2.5% in pigs and 2% to 4% in humans. Hence, our data suggested that the relation of the human liver/body weight is similar to the pig liver/body weight.…”