The in vitro and in vivo effects of anti-galactose antibodies on endothelial cell activation and xenograft rejection.

Xu H, Yin D, Naziruddin B, Chen L, Stark A, Wei Y, Lei Y, Shen J, Logan JS, Byrne GW, Chong AS
J Immunol. 2003 170 (3): 1531-9

PMID: 12538718 · DOI:10.4049/jimmunol.170.3.1531

We have previously produced a series of antigalactose (anti-Gal) hybridomas and characterized their heavy chain gene usage. Here we have quantified the affinity of these Abs for the alpha-Gal epitope and characterized their in vitro effects on endothelial cell activation and apoptosis. We report that anti-Gal mAbs derived from Gal(-/-) mice show a range of affinity for the alpha-Gal epitope, and that affinity was generally increased as the V(H) gene usage transitioned from germline sequences to sequences exhibiting somatic maturation. Despite an 85-fold range in affinity, all the anti-Gal mAbs examined induced alpha-Gal-specific endothelial cell activation, and after prolonged exposure induced endothelial cell apoptosis in a complement-independent manner. Only murine anti-Gal mAbs of the IgM or IgG3 subclass, but not IgG1, were effective at initiating complement-dependent cell lysis. Using a novel rat to mouse xenograft model, we examined the in vivo ability of these mAbs to induce xenograft rejection and characterized the rejection using histology and immunohistochemistry. Infusion of complement-fixing IgG3 mAbs resulted in either hyperacute rejection or acute vascular rejection of the xenograft. Surprisingly, infusion of an equal amount of a high affinity anti-Gal IgG1 mAb, that fixed complement poorly also induced a rapid xenograft rejection, which we have labeled very acute rejection. These studies emphasize the importance of in vivo assays, in addition to in vitro assays, in understanding the role of anti-Gal IgG-mediated tissue injury and xenograft rejection.

MeSH Terms (23)

Animals Antibodies, Monoclonal Antibody Affinity Apoptosis Binding Sites, Antibody Cell Line Disaccharides DNA-Binding Proteins Endothelium, Vascular Erythrocytes Graft Rejection Heart Transplantation Humans Hybridomas Injections, Intravenous Mice Mice, Knockout Nuclear Proteins Rats Rats, Inbred Lew Swine Transplantation, Heterologous Transplantation, Heterotopic

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