Reactivity of human natural antibodies to endothelial cells from Galalpha(1,3)Gal-deficient pigs.
BACKGROUND
Xenoreactive human natural antibodies (NAb) are predominantly directed against galactose-alpha(1,3)galactose (Gal). Binding of immunoglobulin (Ig) G and IgM NAb activates porcine endothelial cells (pEC) and triggers complement lysis responsible for hyperacute xenograft rejection. In vitro, IgG NAb induce human natural killer (NK) cell-mediated lysis of pEC by antibody-dependent cell-mediated cytotoxicity (ADCC). The present study examined the levels of anti-porcine NAb in a large number of individuals and addressed the functional role of non-Gal anti-porcine NAb.


METHODS
Sera from 120 healthy human blood donors were analyzed for the presence of anti-porcine NAb by flow cytometry using porcine red blood cells (pRBC), lymphoblastoid cells (pLCL), and pEC derived from control or Gal-deficient pigs. Xenogeneic complement lysis was measured by flow cytometry using human serum and rabbit complement. ADCC was analyzed by chromium-release assays using human serum and freshly isolated NK cells.


RESULTS
Human IgM binding to pRBC was found in 93% and IgG binding in 86% of all samples. Non-Gal NAb comprised 13% of total IgM and 36% of total IgG binding to pEC. NAb/complement-induced lysis and ADCC of Gal-deficient compared to Gal-positive pEC were 21% and 29%, respectively. The majority of anti-Gal and non-Gal IgG NAb were of the IgG2 subclass.


CONCLUSIONS
The generation of Gal-deficient pigs has overcome hyperacute anti-Gal-mediated xenograft rejection in nonhuman primates. Non-Gal anti-porcine NAb represent a potentially relevant immunological hurdle in a subgroup of individuals by inducing endothelial damage in xenografts.
Baumann
Bettina C
BC
Department of Internal Medicine, Laboratory for Transplantation Immunology, University Hospital, Zurich, Switzerland.
Stussi
Georg
G
Huggel
Katja
K
Rieben
Robert
R
Seebach
Jörg D
JD
D000017:ABO Blood-Group System / Q000276:immunology; D000818:Animals; D030801:Animals, Genetically Modified; D000906:Antibodies / Q000145:classification / Q000276:immunology*; D002478:Cells, Cultured; D003602:Cytotoxicity, Immunologic; D004187:Disaccharides / Q000172:deficiency* / Q000378:metabolism*; D042783:Endothelial Cells / Q000276:immunology* / Q000378:metabolism*; D004912:Erythrocytes / Q000276:immunology; D006801:Humans; D013552:Swine
D000017:ABO Blood-Group System; D000906:Antibodies; D004187:Disaccharides; C055075:galactosyl-(1-3)galactose