Abstract
520 Introduction: Xenoreactive, natural antibodies (XNAb) and activation of complement system are the major trigger for hyperacute xenograft rejection (HXR) after xenotransplantation (XT) of porcine hearts. Removal of these XNAb with immunoadsorption (IA) using the Ig-Therasorb® column was investigated in a working heart model of pig hearts perfused with human blood. Material and methods: Hearts of 12 landrace pigs (weight 22.5±3.8 kg) were explanted after cardioplegic arrest (induced by 4°C Celsior-solution) and were perfused with human blood (500 ml, heparinized) under afterload conditions in the working heart mode. In group 1 (G1) 6 pig hearts were perfused with untreated blood. In group G2 (n = 6) donor blood was separated into plasma and cellular components. Plasma passed twice Ig-Therasorb column to remove IgG, IgM and IgA. In working heart modus hemodynamic parameters (arterial blood pressure, heart rate, cardiac output (CO), stroke work index (SWI), coronary flow/resistance (CF/CR) and arteriovenous oxygen difference (AVDO2) were measured. Blood samples were taken for determination of CK(-MB), LDH, ASAT, immunoglobulins, anti pig antibodies (XNAb), complement factors C3 and C4, complement activity CH50 and AP50. After cardiac arrest tissue was sampled for histological examination (light and electron microscopy, immunohistochemical analysis). Results: Two cycles of IA removed IgG by 84%, IgM by 83%, IgA by 76% and complement C3 and C4 by more than 50% in G2. IA also reduced anti pig antibodies by 84%, whereas in control group G1 XNAb disappeared after 60 min of organ perfusion, IgM immunoglobulin level increased after 3 hours and complement was consumpted after 60 min (p<0.05). Complement activity decreased in G2 after IA. In G1 the decrease was caused by HXR after 30 to 90 min of perfusion. Levels of cardiac enzymes tended to be higher in G1 (n.s.). Histological examination showed typical signs of HXR with marked deposits of IgM, C3, C4 and C5b-9 in the myocardium of G1. In G2 cardiomyocytes showed only slight unspecific damages. In contrast to G1 with cardiac arrest after 125±31.3 min mean perfusion time in IA group G2 was significantly longer (335±37.5 min). Hemodynamic parameters of cardiac xenograft function after IA were significantly improved: CO was 118%, CF 154% and heart rate 12% higher than in G1, whereas CR and AVDO2 (n.s.) were lower. The heart weight increase in G1 was significantly higher than G2 (G1:0.4±0.08 %/h vs. G2: 0.09±0.02%/h). Discussion: Antibody and complement removal by IA resulted in no histological evidence of HXR and in significantly improved xenograft function and perfusion time in a working heart model. IA has the potential to prevent HXR after XT. Ig-Therasorb columns are an ideal additional treatment of HXR after XT in primates and future clinical XT combined with hDAF-transgeneic pig hearts.
Published Version
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