The Red Cell Phenotype En(a‐) and Anti‐En^a: Serological and Physicochemical Aspects

Abstract

Summary. The lack of the very common red cell antigen Ena is a rare recessive character. En(a‐) cells are further unusual in having only about 33% of the normal amount of sialic acid and in having an electrophoretic mobility about 60% of normal. These abnormalities adequately explain other peculiarities of En(a‐) cells: their weak MN antigens, their ability to be agglutinated, though suspended in saline, by appropriate incomplete Rh antisera, and their preferential agglutination by certain seed extracts and non‐immune animal sera. Ena is antigenic in rabbit as well as in man: an attempt to stimulate in a rabbit an antibody specific for En(a‐) cells did not succeed. The locus responsible for Ena is shown to be genetically independent of the loci for ABO, MNSs, Rh, Duffy and haptoglobins and not to be X‐ or Y‐linked. En(a+) hetereozygous cells show some of the changes of En(a‐) cells, in a modified but recognizable way. The physicochemical background and the nature of the genetic defect in this unusual blood group system are discussed.

Comparison of Electrophoretic Mobility and Membrane Sialic Acid Content of Erythrocytes from Adult and Umbilical Cord Blood

“…Cells of the rare M N variants Mg, Mk (9,12), Miltenberger classes I I I and V (9), as well as cells lacking the public Ena antigen (5,9) and Tn polyagglutinable cells (1 1, 16), exhibit, in addition to their serologic abnormalities, aberrant values for membrane sialic acid content and electrophoretic mobility. In these abnormal cells, as well as in the case of neuraminidase-treated cells (4, lo), the Prinrrd rn U .…”

The Action of Seed and Other Reagents on HEMPAS Erythrocytes

“…En(a-) cells are not polyagglutinable. They are agglutinated in saline by 'incomplete' Rhesus antibodies and by the lectin of Sophora japonica [9]. We found that HEMPAS cells (M. F.) were not agglutinated either by 'incomplete' Rhesus antibodies in saline or by the Sophora japonica lectin which reacts strongly with En(a-) cells or those of En(a+) heterozygotes; this was first observed by Sanger [13] who also observed that these cells in saline do not react with incom plete anti-D, unlike En(a-) or En(a+) heterozygous cells, that they react ed normally with rabbit or human anti-Ena and reacted more strongly than a normal NN control with Vicia graminea and Bauhinia purpurea lectins.…”

AFA-I, a cloned afimbrial X-type adhesin from a human pyelonephritic Escherichia coli strain. Purification and chemical, functional and serlologic characterization

“…In addition to its capacity to agglutinate NN erythrocytes, AFA-I was further distinguished from the M adhesin by the failure of purified glycophorin A to bind AFA-I or to inhibit AFA-I hemagglutination. Furthermore AFA-I agglutinated En(a-) red cells, which have reduced M and N activity [20] due to the decreased content of sialic acid and are markedby deficient in glycophorin A. Similarly, some E. c d i strains agglutinate human erythrocytes by binding sialyl-(2-3/6)-lactose residues.…”