Involvement of the MN blood group antigen in shear-enhanced hemagglutination induced by the Escherichia coli F41 adhesin.

An adhesin from Escherichia coli F41 with an apparent subunit molecular weight of 28,000 daltons was isolated by using (NH4)2SO4 precipitation at pH 10 and Sephacryl S-500 gel filtration. The hemagglutination (HA) properties of the native high-molecular-weight adhesin were studied by using a viscometric assay, which provided a quantitative index of the degree of agglutination present as a function of time at a known rate of shear. Shear was found to enhance the degree of agglutination over a 20-min period. A strong, shear-enhanced HA was observed for all donors with the MM or MN blood type studied, but those with the NN blood type showed very little HA. In the microtiter HA assay, the selectivity of the adhesin for MM over NN erythrocytes was found to be dependent on pH and temperature. At 21 degrees C and pH 7.4, there was little difference in HA between the two blood types, but NN cells were progressively more weakly agglutinated than MM cells as the pH or the temperature was increased. Glycophorin A, which bears the M or N determinant, was isolated from individuals with the MM and NN blood types and was shown to be an effective inhibitor of the reaction, with the MM type being the more effective in both microtiter and viscometric assays. Acidic monosaccharides, particularly sialic acid, were also effective inhibitors of HA, although they were less potent on a molar basis than glycophorin. The adsorption isotherm of 125I-labeled adhesin was measured, and the binding was shown to be strongly inhibited by MM glycophorin and somewhat less strongly by NN glycophorin. Collectively, these data strongly suggest that glycophorin AM is a receptor for the F41 adhesin.