Role of anti-Galα1,3Gal and anti–platelet antibodies in hyperacute rejection of pig lung by human blood

Background. Previous work has shown that antibodies against porcine antigens are an important trigger of hyperacute lung rejection (HALR). The relative importance of Galα1,3Gal epitopes and other antigens, such as those expressed on pig platelet membranes or lung itself, has not been defined. This study compares the efficiency of three anti–pig antibody depletion strategies, and their efficacy with regard to attenuation of HALR. Methods. Plasma pooled from three human donors was adsorbed against Galα1,3Gal disaccharide or porcine platelet extract (PPE), or passed through pig lung vasculature. Whole blood reconstituted using adsorbed plasma was then used to perfuse piglet lung, and results were compared with unmodified human blood. Results. Depletion of lung-reactive anti–Galα1-3Gal antibodies was most efficient with the αGal column (99% ± 0.5% vs 87% to 93% ± 11% for PPE and 92% to 95% ± 8% for lung, p < 0.01 vs αGal column). PPE column tended to be more efficient (77% to 84% ± 12%) in removing anti-PPE antibodies than pig lung (66% to 70% ± 14%) or the αGal column (56% to 63% ± 16%, p < 0.05). Lung survival and function with each antibody depletion strategy was improved relative to unmodified controls (mean survival ≥146 minutes vs 8 minutes for controls). Although αGal and lung adsorption yielded more consistent lung protection (survival beyond 2 hours) than did PPE, no approach proved significantly superior. Complement C3a elaboration at 10 minutes was attenuated >80% by each adsorption strategy, an effect that was most pronounced in the lung adsorption group (95%, p < 0.01). Histamine elaboration was blunted significantly by PPE adsorption but not in other groups (p < 0.05). Platelet but not leukocyte sequestration was decreased with antibody depletion compared with the nondepleted group (44% to 50% vs 82%, p < 0.01). Conclusions. Each antibody depletion strategy tested significantly prolongs lung xenograft survival and function compared with unmodified human blood, but none was sufficient to reliably prevent HALR. Depletion of antibodies against both αGal and additional cell membrane antigens, or control of antibody-independent pathogenic pathways, may be necessary to consistently prevent HALR.