Regulation of complement-mediated swine endothelial cell lysis by a surface-bound form of human C4b binding protein.
BACKGROUND
Human C4b-binding protein (C4bp) functions as a cofactor for factor I in the degradation of C4b and C3b and, in addition, accelerates the rate of decay of the C4b2a complex.


METHODS
In this study, we constructed a surface-bound form of human C4b-binding protein (C4bp-PI) consisting of a short consensus repeat 1-8 of the alpha-chain of C4bp and a glycosyl phosphatidylinositol (GPI) of the decay-accelerating factor (CD55) and established stable swine endothelial cell (SEC) lines expressing C4bp-PI by transfection of cDNA. Amelioration of complement-mediated lysis by the transfectant molecules was tested as an in vitro hyperacute rejection model of swine to human discordant xenograft, using the lactate dehydrogenase assay.


RESULTS
Flow cytometric profiles of the stable SEC lines with C4bp-PI showed a high level of expression of this molecule. The cell lysate of the SEC line with C4bp-PI showed strong cofactor activity in not only C4b but also C3b, whereas the activity of plasma C4bp to bind to C3 was very weak. Approximately 150 x 10(4) molecules of C4bp-PI per SEC blocked human complement-mediated cell lysis by approximately 75%.


CONCLUSIONS
The results suggest that the surface-bound form of C4bp will be very useful in clinical xenotransplantation.
Mikata
S
S
Department of Immunology, Center for Adult Diseases, Osaka, Japan.
Miyagawa
S
S
Iwata
K
K
Nagasawa
S
S
Hatanaka
M
M
Matsumoto
M
M
Kamiike
W
W
Matsuda
H
H
Shirakura
R
R
Seya
T
T
D000818:Animals; D001483:Base Sequence; D018958:CD55 Antigens / Q000096:biosynthesis; D002462:Cell Membrane / Q000502:physiology; D015935:Complement C4b / Q000378:metabolism*; D003169:Complement Inactivator Proteins; D004730:Endothelium, Vascular / Q000166:cytology* / Q000473:pathology / Q000502:physiology*; D006023:Glycoproteins; D017261:Glycosylphosphatidylinositols / Q000096:biosynthesis; D006084:Graft Rejection / Q000276:immunology*; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D055503:Protein Multimerization; D011951:Receptors, Complement / Q000096:biosynthesis / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D013552:Swine; D014162:Transfection; D014183:Transplantation, Heterologous / Q000276:immunology / Q000502:physiology*
D018958:CD55 Antigens; D003169:Complement Inactivator Proteins; D006023:Glycoproteins; D017261:Glycosylphosphatidylinositols; D009838:Oligodeoxyribonucleotides; D011951:Receptors, Complement; D011993:Recombinant Fusion Proteins; D015935:Complement C4b