Search PubMed⌕ Search

Biomedical subjects

T Cairns

Publications and source records attributed to T Cairns.

At least 19 recordsLinked to original sources
PubMed1999

Inhibition of expression of the Galalpha1-3Gal epitope on porcine cells using an intracellular single-chain antibody directed against alpha1,3galactosyltransferase.

The carbohydrate epitope Galalpha1-3Gal has been shown to be the major target of natural antibodies responsible for hyperacute rejection of porcine tissues transplanted into primates. We have sought to produce a phenotypic knockout of the alpha1, 3Galactosyltransferase enzyme that is responsible for generating this epitope, using an intracellular antibody approach. We have isolated high affinity anti-alpha1,3Galactosyltransferase single-chain antibodies from a semi-synthetic phage display library. Expression of a KDEL-tagged anti-alpha1,3Galactosyltransferase single-chain antibody in a porcine endothelial cell line resulted in the decreased expression of the Galalpha1-3Gal epitope and increased resistance to lysis by human serum.

Amino Acid Sequence↗
PubMed1999

Chloramine-induced haemolysis presenting as erythropoietin resistance.

BACKGROUND: In December 1996 we identified an outbreak of erythropoietin (rHuEpo) resistance requiring a substantial increase in rHuEpo dosage in one of our four haemodialysis (HD) units. The dialysate chloramine levels in this unit had risen from <0.1 p.p.m. in 1996 to 0.25-0.3 p.p.m. in 1997. In the other three HD units levels remained <0.1 p.p.m. Other parameters of water quality were within accepted standards. METHODS: Monthly records of haemoglobin level and rHuEpo dose were available for 148 patients between January 1996 and May 1998. Seventy-two patients, with no recognized cause of rHuEpo resistance, were analysed in detail (August 1997 to April 1998). A subgroup of 15 patients was examined for evidence of haemolysis during HD (methaemoglobin and haptoglobin levels, reticulocyte counts and Heinz bodies). Larger carbon columns were installed in December 1997 to effect chloramine removal. RESULTS: There was an increase in mean methaemoglobinaemia of 23% (P<0.01) and a 21% fall in mean haptoglobin (P<0.01) across HD, although no patient had a reticulocytosis and only one patient with G6PD deficiency had Heinz bodies. Following installation of larger carbon columns there was an 18.6% rise (P<0.001) in mean haemoglobin level and a subsequent 25.0% reduction (P<0.001) in mean rHuEpo dose. Intradialytic changes in methaemoglobin and haptoglobin were abolished. The dialysate chloramine levels fell to < 0.1 p.p.m. Water company records subsequently revealed a sustained twofold increase in mains water chloramine from November 1996. CONCLUSIONS: This is the first report linking chloramine exposure and rHuEpo resistance, with only subtle signs of haemolysis. Unheralded changes in mains water constituents can directly affect dialysate water quality and clinical outcomes.

Adult↗
PubMed1998

Demonstration of IgM antibodies of high affinity within the anti-Galalpha1-3Gal antibody repertoire.

BACKGROUND: Human anti-Galalpha1-3Gal IgG and IgM xenoantibodies can distinguish between very similar epitopes with a high degree of selectivity. METHODS: Anti-Galalpha1-3Gal antibodies were affinity isolated using two separate Galalpha1-3Gal-based immunoadsorbents, Galalpha1-3Gal itself and Galalpha1-3Galbeta1-4Glc. IgG and IgM were separated using a protein G column. Antibody purity was achieved by serial adsorption/elutions from the columns. By this means, different antibody fractions were prepared that contained either IgG or IgM, reactive with either Galalpha1-3Gal, Galalpha1-3Galbeta1-4Glc, or both. The dissociation equilibrium constants (Kd) of these antibodies were then measured using an IAsys biosensor. RESULTS AND CONCLUSIONS: Sera from two individuals were used and Kd values for one IgG (fraction 1A) and two IgM (fractions 1B and 2A) fractions were obtained. The Kd for the IgG was 4.85 x 10(-7) M (fraction 1A). For IgM, the Kd values were higher at 7.8x10(-10) M (fraction 1B) and 1.07x10(-10) M (fraction 2A). Natural anti-pig antibodies include high affinity IgM that continue to be produced without class switch. The B cell mechanism behind this is not known. It may be possible to exploit this mechanism in future xenotransplantation strategies.

Antibodies↗
PubMed1998

Polymorphism in the human anti-pig natural antibody repertoire: implications for antigen-specific immunoadsorption.

BACKGROUND: Anti-Galalpha1-3Gal antibodies cause hyperacute rejection (HAR) in pig-to-primate xenotransplantation. Long-term graft survival has not been achieved despite abrogation of HAR using transgenic pigs. IgG and IgM anti-Galalpha1-3Gal also play a role in the events following abrogation of HAR. Characterizing these antibodies and developing a system for their removal is therefore crucial to future success in xenotransplantation. METHODS AND RESULTS: We have developed a neoglycoprotein enzyme-linked immunosorbent assay to probe the precise antigenic requirements for the binding of anti-Galalpha1-3Gal and have analyzed 77 normal sera. Sixty-six percent of individuals have IgG that recognizes the Galalpha1-3Gal di-, tri-, and pentasaccharides (D, T, and P, respectively), termed DTP phenotype. The frequency of other phenotypes was - -P, 13%; -TP, 12%; D-P, 8%; and DT-, 1%. The IgG subclasses found were IgG2 (95%), IgG3 (34%), IgG1 (31%), and IgG4 (17%). IgM in 91% of individuals recognized all three antigens. Further antibody heterogeneity was demonstrated when immunoadsorbents derived from Galalpha1-3Galbeta1-4GlcNAcbeta1-3Galbeta1-4Glc (PENTA) were tested. Galalpha1-3Galbeta1-4Glc (TRI 6) or PENTA agarose were effective for IgG removal in all individuals. For IgM removal, two deoxy derivatives were completely successful in 73% of individuals. Combining the Galalpha1-3Gal (DI) and TRI 6 agarose produced an adsorbent that completely removed anti-Galalpha1-3Gal IgG and IgM in all individuals tested. CONCLUSIONS: Although the polymorphism in the anti-Galalpha1-3Gal repertoire, which we have demonstrated, represents a major obstacle to the development of an effective immunoadsorbent, the combination of DI and TRI 6 agarose appears sufficient for pig-to-human xenotransplantation.

Animals↗
PubMed1995

Inhibition of the pig to human xenograft reaction, using soluble Gal alpha 1-3Gal and Gal alpha 1-3Gal beta 1-4GlcNAc.

Natural anti-carbohydrate antibodies are central to hyperacute rejection in ABO-incompatible allotransplantation and in discordant xenotransplantation. ABO-incompatible rejection has been inhibited successfully using intravenous soluble carbohydrates as antibody inhibitors. The approach has been less successful previously in pig to primate xenotransplantation, where the necessary concentrations of a partial inhibitor (Gal alpha 1-6Glc) proved highly toxic. In this study, we have identified more effective inhibitors of the dominant human anti-pig antibodies that bind to the pentasaccharide Gal alpha 1-3Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4Glc beta 1-. The inhibitors are the terminal disaccharide (Gal alpha 1-3Gal) and terminal trisaccharide (Gal alpha 1-3Gal beta 1-4GlcNAc) of the target pentasaccharide. Twelve sera (3 from each ABO blood group) were tested in 3 different assays: lymphocytotoxic, lymphocyte flow cytometry, and solid-phase antigen ELISA. Fifty percent to 75% inhibition of human IgG and IgM was achieved using the disaccharide and trisaccharide inhibitors in the range of 10-50 mM. Disaccharide (70 mM) was used to inhibit hyperacute thrombosis in pig kidneys perfused for 40 min with heparinized human AB whole blood. The disaccharide completely inhibited red cell occlusion of glomerular but not of intertubular capillaries, although there was residual platelet thrombus in glomeruli. Disaccharide and trisaccharide can, therefore, be used in concentrations shown for other carbohydrate inhibitors to be nontoxic, for inhibition of hyperacute pig-to-human xenograft rejection. The inhibition is incomplete, however, and other antigen specificities and other rejection mechanisms are likely to be involved.

ABO Blood-Group System↗