Carbohydrate residues downstream of the terminal Galalpha(1,3)Gal epitope modulate the specificity of xenoreactive antibodies

TY - JOUR

T1 - Carbohydrate residues downstream of the terminal Galalpha(1,3)Gal epitope modulate the specificity of xenoreactive antibodies

AU - Milland, Julie

AU - Yuriev, Elizabeth

AU - Xing, Pei-Xiang

AU - McKenzie, Ian

AU - Ramsland, Paul A

AU - Sandrin, Mauro Sergio

PY - 2007

Y1 - 2007

N2 - Carbohydrates are involved in many immunological responses including the rejection of incompatible blood, tissues and organs. Carbohydrate antigens with Gal alpha(1,3)Gal epitopes are recognized by natural antibodies in humans and pose a major barrier for pig-to-human xenotransplantation. Genetically modified pigs have been established that have no functional alpha 1,3galactosyltransferase (alpha 1,3GT), which transfers alpha Gal to N-acetyllactosamine ( LacNAc) type oligosaccharides. However, a low level of Gala( 1,3) Gal is still expressed in a1,3GT knockout animals in the form of a lipid, isoglobotrihexosylceramide (iGb3), which is produced by iGb3 synthase on lactose ( Lac) type core structures. Here, we define the reactivity of a series of monoclonal antibodies (mAb) generated in alpha 1,3GT-/- mice immunized with rabbit red blood cells (RbRBC), as a rich source of lipid-linked antigens. Interestingly, one mAb (15.101) binds weakly to synthetic and cell surface-expressed Gal alpha(1,3)Gal on LacNAc, but strongly to versions of the antigen on Lac cores, including iGb3. Three-dimensional models suggest that the terminal alpha-linked Gal binds tightly into the antibody-binding cavity. Furthermore, antibody interactions were predicted with the second and third monosaccharide units. Collectively, our findings suggest that although the terminal carbohydrate residues confer most of the binding affinity, the fine specificity is determined by subsequent residues in the oligosaccharide.

AB - Carbohydrates are involved in many immunological responses including the rejection of incompatible blood, tissues and organs. Carbohydrate antigens with Gal alpha(1,3)Gal epitopes are recognized by natural antibodies in humans and pose a major barrier for pig-to-human xenotransplantation. Genetically modified pigs have been established that have no functional alpha 1,3galactosyltransferase (alpha 1,3GT), which transfers alpha Gal to N-acetyllactosamine ( LacNAc) type oligosaccharides. However, a low level of Gala( 1,3) Gal is still expressed in a1,3GT knockout animals in the form of a lipid, isoglobotrihexosylceramide (iGb3), which is produced by iGb3 synthase on lactose ( Lac) type core structures. Here, we define the reactivity of a series of monoclonal antibodies (mAb) generated in alpha 1,3GT-/- mice immunized with rabbit red blood cells (RbRBC), as a rich source of lipid-linked antigens. Interestingly, one mAb (15.101) binds weakly to synthetic and cell surface-expressed Gal alpha(1,3)Gal on LacNAc, but strongly to versions of the antigen on Lac cores, including iGb3. Three-dimensional models suggest that the terminal alpha-linked Gal binds tightly into the antibody-binding cavity. Furthermore, antibody interactions were predicted with the second and third monosaccharide units. Collectively, our findings suggest that although the terminal carbohydrate residues confer most of the binding affinity, the fine specificity is determined by subsequent residues in the oligosaccharide.

UR - http://www.nature.com/icb/journal/v85/n8/full/7100111a.html

U2 - 10.1038/sj.icb.7100111

DO - 10.1038/sj.icb.7100111

M3 - Article

VL - 85

SP - 623

EP - 632

JO - Immunology and Cell Biology

JF - Immunology and Cell Biology

SN - 0818-9641

IS - 8

ER -