Combination of decay-accelerating factor expression and alpha1,3-galactosyltransferase knockout affords added protection from human complement-mediated injury.
BACKGROUND
Hyperacute rejection (HAR) currently prevents the use of pigs as organ donors for humans. It is now generally accepted that the key instigators of HAR are naturally occurring xenoantibodies against the terminal disaccharide galactose alpha1,3-galactose (Gal), and the species incompatibility between human complement and porcine complement regulatory molecules. Using two in vitro models and an ex vivo mouse heart perfusion model, we have shown previously that cells and tissues from Gal knockout (Gal KO) and transgenic mice expressing the human cell surface complement regulator decay-accelerating factor (DAF/CD55) are partially, but not completely, protected from human complement-mediated injury.


METHODS
In the present study, Gal KO mice were crossed with DAF transgenic mice and bred to homozygosity (DAF/Gal KO). Isolated splenocytes were incubated with human serum, and the protective effect of DAF and Gal KO was assessed by measuring complement deposition and cell lysis. Hearts perfused ex vivo with human plasma were examined for human antibody and complement deposition, and assessed functionally by measuring work performed by the heart.


RESULTS
Splenocytes from DAF/Gal KO mice were found to be more resistant to complement-mediated injury than cells from either DAF transgenic or Gal KO mice. In addition, hearts from DAF/Gal KO mice, when perfused with human plasma, displayed prolonged survival compared with hearts from Gal KO mice. This was associated with a reduction in the extent of endothelial deposition of IgG, IgM, and complement C3b.


CONCLUSIONS
These findings demonstrate that expression of human DAF in association with elimination of the Gal epitope provides added protection from complement-mediated injury in these models of HAR.
van Denderen
B J
BJ
Immunology Research Centre, St. Vincent's Hospital, Fitzroy, Victoria, Australia. bryce.van.denderen@nantes.inserm.fr.
Salvaris
E
E
Romanella
M
M
Aminian
A
A
Katerelos
M
M
Tange
M J
MJ
Pearse
M J
MJ
d'Apice
A J
AJ
D000818:Animals; D018958:CD55 Antigens / Q000096:biosynthesis* / Q000235:genetics; D002470:Cell Survival; D002478:Cells, Cultured; D003176:Complement C3 / Q000378:metabolism; D003165:Complement System Proteins / Q000633:toxicity*; D004730:Endothelium, Vascular / Q000276:immunology / Q000378:metabolism; D000939:Epitopes; D005700:Galactosyltransferases / Q000172:deficiency* / Q000235:genetics; D006720:Homozygote; D006801:Humans; D008214:Lymphocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009206:Myocardium; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000032:analysis / Q000096:biosynthesis; D013154:Spleen / Q000276:immunology; D013552:Swine; D014183:Transplantation, Heterologous
D018958:CD55 Antigens; D003176:Complement C3; D000939:Epitopes; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D003165:Complement System Proteins; D005700:Galactosyltransferases; C038887:N-acetyllactosamine alpha-D-galactosyltransferase