We have previously shown that when porcine livers are perfused with human blood, porcine Kupffer cells extract up to 3 units of human erythrocytes over the course of a 72 hr perfusion. We have previously hypothesized that the recognition event responsible for this interaction involves a lectin receptor on the surface of the porcine Kupffer cell interacting with a carbohydrate epitope on the surface of the human erythrocytes.Treatments to disrupt the protein core of purified glycoproteins from the surface of human erythrocytes included: pronase, trypsin, beta-mercaptoethanol (2-ME), and heating to 90 degrees . Alternatively, we have removed the carbohydrate residues from purified human red blood cell (RBC) glycoproteins using glycosidases. Erythrocyte binding in the presence or absence of treated glycoproteins was quantified by Chromium-labeled RBC recognition by primary cultures of porcine Kupffer cells.Human, but not porcine, erythrocytes were bound by in vitro primary cultures of porcine Kupffer cells. Binding was inhibited by preincubation of porcine Kupffer cells with purified human erythrocyte glycoproteins (hEGP) from human erythrocyte membranes. Pretreatment of human EGP with pronase, trypsin, 2-ME, or heating did not interfere with the ability of human EGP to inhibit the binding of human erythrocytes to porcine Kupffer cells. Deglycosylation of the purified hEGP completely disrupted hEGP ability to inhibit the binding of human erythrocytes to porcine Kupffer cells.We conclude that porcine Kupffer cells bind xenogeneic human RBC by recognition of a carbohydrate epitope on the surface of human erythrocytes. We hypothesize that this binding is mediated by a porcine Kupffer cell lectin receptor.