Studies on the removal of anti‐pig xenoantibodies in the human by plasmapheresis/immunoadsorption

Abstract: Removal of human preformed natural anti‐pig antibodies from the blood is a prerequisite before xenografting between pig and man can be performed. This work explores the effect of plasmapheresis and immunoadsorption (protein‐A sepharose) on the reduction and recurrence of anti‐pig antibodies in 14 patients. The anti‐pig antibody changes were evaluated by lymphocy to toxic, hemagglutinating, and endothelial cell ELISA techniques. The changes induced showed a similar pattern with all three techniques used. In addition, plasma from plasmapheresis treatments were perfused through pig kidneys and the reduction of anti‐pig antibodies was estimated by the mentioned in vitro techniques. The anti‐pig antibody titers could be reduced to low levels, but not completely eliminated, by 3–4 plasmapheresis sessions. The titers gradually returned to pretreatment levels or higher in a period of 1–2 weeks. A few patients showed signs of a more rapid resynthesis reaching pretransplant levels in 3–4 days. Protein A immunoadsorption satisfactory removed IgG but not IgM antibodies. In vitro perfusion of pig kidneys at 37°C showed a rapid reduction of anti‐pig antibody titers of 3–4 titer steps. The combination of 3–4 plasma exchanges followed by in vitro pig kidney perfusion completely removed all anti‐pig antibodies. Reduction of the anti‐pig lymphocyte and erythrocyte antibody titers by soluble oligosaccharides carrying terminal Galoc‐epitopes was only partly successful. A 40–60% inhibition was achieved by 5–10 mg saccharide/ml serum and no clear inhibition difference between di‐ and trisaccharides was found. Inhibition of plasma obtained after 3–4 plasmapheresis treatments with soluble Galα1‐di‐ and trisaccharides resulted in very low anti‐pig titers. Therefore one feasible pretreatment procedure, before pig to human xenotransplantation could be plasmapheresis for major reduction of anti‐pig antibody titer followed by neutralisation of the remaining antibodies by addition of soluble oligosaccharides or immunoadsorption with Galα‐1‐columns.