Figure 7. Influence of special cardioplegic solutions on xenograft endothelial cell surface. We suggest 3 theories explaining the reduced antigen-antibody interaction on porcine aortic endothelial cells: It is possible that cardioplegic solutions (1) cause structural changes on the endothelial cell surface, (2) result in a detachment (shedding) of Galα1-3Galβ1-4GlcNAc-Rs, or (3) coat the endothelial surface.