Anti-Gal antibodies in humans and 1, 3alpha-galactosyltransferase knock-out mice.
BACKGROUND
Due to the absence of alphaGAL epitopes, humans and galactosyltransferase knock-out (GALT/ KO) mice express high levels of anti-Gal antibodies. We describe the properties of mouse anti-GAL antibodies.


METHODS
Anti-GAL IgG antibodies were quantified by affinity purification. Antibody affinities and avidities were determined in direct binding and competition assays. Antibody-mediated rejection was investigated using hyperimmunized GALT/KO mice as recipients of GAL+ heart allografts.


RESULTS
In young GALT/KO mice the levels of anti-GAL antibodies were low. Immunization of GALT/KO mice resulted in increased anti-GAL antibody expression. In mouse serum 0.6% of IgG was specific for alphaGAL compared to 0.5% in human serum. The avidity of purified mouse and human anti-GAL IgG was 30 and 6 nM, the affinity 15 and 50 microM, respectively. The isotype distribution in mouse and human anti-GAL IgG appeared to be similar to the isotype distribution in normal sera. The affinity of mouse and human anti-GAL IgM was 150 and 750 microM, respectively. Immunized GALT/KO recipients of GAL+ heart transplants rejected their grafts within 2 hr although nonimmunized GALT/KO mice retained their grafts for up to 6 days. Immunohistological examination of the rejected GAL+ hearts revealed massive deposition of IgM and IgG on endothelial cells of the graft with a concomitant deposition of complement.


CONCLUSIONS
Our studies demonstrate that anti-GAL antibodies from immunized GALT/KO mice bind alphaGAL with an avidity/affinity similar to human anti-GAL antibodies and are able to induce hyperacute rejection of GAL+ heart allografts.
Chiang
T R
TR
SangStat Medical Corp, Fremont, CA 94555, USA.
Fanget
L
L
Gregory
R
R
Tang
Y
Y
Ardiet
D L
DL
Gao
L
L
Meschter
C
C
Kozikowski
A P
AP
Buelow
R
R
Vuist
W M
WM
D000818:Animals; D005700:Galactosyltransferases / Q000172:deficiency* / Q000235:genetics; D006084:Graft Rejection; D016027:Heart Transplantation / Q000276:immunology; D006801:Humans; D007114:Immunization; D007074:Immunoglobulin G / Q000097:blood*; D007075:Immunoglobulin M / Q000097:blood*; D051379:Mice; D018345:Mice, Knockout; D011817:Rabbits; D014312:Trisaccharides / Q000276:immunology*
D007074:Immunoglobulin G; D007075:Immunoglobulin M; D014312:Trisaccharides; C076569:alpha-galactosyl epitope; D005700:Galactosyltransferases; C037959:beta-D-galactosyl-N-acetylglucosaminylglycopeptide alpha-1,3-galactosyltransferase