An attempt to identify the intestinal receptor for the K88 adhesin by means of a haemagglutination inhibition test using glycoproteins and fractions from sow colostrum.

The K88 antigen of Escherichia coli specifically adheres to the piglet intestinal cell; a solution of this antigen agglutinates guinea-pig red cells at 4 degrees C. The latter reaction was used as a model of the former, using inhibition of haemagglutination as an index of specific combination with the K88 adhesin. Inhibition was found with mucous glycoproteins and chemical modification of their heterosaccharide residues by mild acid hydrolysis, periodate oxidation or the Smith degradation procedure suggested that the terminal beta-D-galactosyl structure in a heterosaccharide sidechain of a glycoprotein might combine specifically with the K88 adhesin and inhibit haemagglutination. One serum glycoprotein (fetuin), after exposure of its subterminal beta-D-galactosyl residue, also inhibited haemagglutination, but high inhibitory activity was exhibited by some submaxillary glycoproteins in which this structure was absent or not prominent. It was concluded that in some cases inhibition of haemagglutination by glycoprotein was non-specific. No inhibition was found using glycosaminoglycans, glycogen or any simple sugar or glycoside. Sow colostrum was inhibitory but this was associated mainly with its gamma-globulin fraction. Some inhibitory activity was traced to a colostral glycopeptide fraction of low molecular weight but the smaller colostral oligosaccharides were not inhibitory; the composition of these components in sow colostrum is reported.