The Rare Phenotype En(a-) in a French-Canadian Family

Abstract

A French-Canadian En(a- ) propositus, whose red cells are phenotypically like the three previously reported, differs in the mode of reaction of this antibody which is apparently not immune. His consanguineous parents and 2 of this 4 sibs are heterozygous En^a En, the other 2 being En^a En^a. Sialic acid levels and the MN glycoprotein content of the red cells of the family and the PAS-stained patterns of the red cell membranes of the propositus confirm the serological findings.

Another individual (J.R.) whose red blood cells appear to carry a hybrid MNSs sialoglycoprotein

“…Indeed, it is already known that the R.L. 35 anti-Ena can be totally inhibited by SGP preparations, and does not react with papain or trypsin-treated red blood cells. Presumably this anti-Ena is an anti-MN SGP defining a portion of the normal MN SGP that is intact in SGP isolates, but is no longer detected on red blood cells that have been treated with trypsin or papain.…”

MNS Blood Group System

“…Three possible En heterozygotes were found by screening 6202 donors by direct agglutination of their red cells with ' incomplete ' anti -D and anti -c (see above) [118] . Two other En(a − ) propositi with anti -En a , a French Canadian [106] and a Pakistani [107] , have been reported. Two other En(a − ) propositi with anti -En a , a French Canadian [106] and a Pakistani [107] , have been reported.…”

“…None of the four En(a− ) siblings of the three propositi had made anti -En a ; none had been transfused, but one had been pregnant fi ve times. The French -Canadian En(a − ) propositus (RL), a man with no transfusion history, made anti -En a and no anti -Wr b ; his anti -En a differed from the other examples in that it defi ned a trypsin -sensitive antigen and could be inhibited by extracted M and N substances [106] . Neither antibody reacted with cells of the En(a − ) Wr(a − b − ) phenotype, but anti -En a , unlike anti -Wr b , did react with En(a + ) Wr(a + b − ) cells (described below).…”

“…Anti -En a TS recognises a T rypsin -S ensitive determinant and is typifi ed by the antibody of the French -Canadian En(a − ) propositus (RL) [106] . It does not react with En(a + ) red cells treated with trypsin, fi cin, or papain and can be inhibited by isolated GPA and reacts with a determinant around amino acid residues 31 -39, but only on those GPA molecules that are not glycosylated at Thr33 [40] .…”

“…Pr 2 and Sa are also detected on red cell gangliosides [169] . Pr antibodies agglutinate En(a − ) cells very weakly and do not agglutinate M K cells at all [16,106,171] . Unfortunately, no adsorption/elution studies were performed with M K cells, which would be expected to carry some Pr determinants on other membrane components such as GPC and GPD.…”