Human blood-group A- and H-specified glycosyltransferase levels in the sera of newborn infants and their mothers

A novel observation on grouping anomaly: The phenomena mimicking the Bel genetic variant of the ABO blood groups

BACKGROUND:

Discrepancy in “forward/reverse” grouping leads to confusion in assigning ABO group to a person. It could be genetic in nature and classified according to the presence/absent of antigen on red blood cell (RBC) vis-a-vis corresponding alloantibody in plasma.

AIM:

The aim of the study was to investigate the grouping anomaly found in a recently delivered woman who required transfusion.

MATERIALS AND METHODS:

A standard protocol for investigation was followed.

RESULTS:

A 27-year-old female, gravida 4, para 3, was grouped O on forward grouping, but her serum did not agglutinate Group B RBCs tested. Absorption-elution study gave an active eluate from her sensitized RBCs with anti-B or anti-A+B. Saliva showed H, but no B antigens indicating to her Bel phenotype. However, 2-week latter in the follow-up study, her serum revealed a presence of complement binding high titer anti-B. The problem of missing anti-B on the previous occasion was attributed to hemagglutination inhibition caused by accumulated complement macromolecules on RBCs that gave rise to physical hindrance in the formation hemagglutination clumps.

CONCLUSION:

The unusual case of erroneous reversed grouping was attributed to complement-mediated hemagglutination inhibition. The positive eluate obtained from sensitized RBCs of the mother was considered to be due to a contamination of fetal RBCs in maternal circulation entered during her postpartum phase of pregnancy. It could also be due to a conversion of H to B antigen no matter in trace amount by the fetal B group-specific transferase percolated into maternal circulation.

A laboratory exercise to determine human ABO blood type by noninvasive methods

Analysis of single-nucleotide polymorphisms and their association with diseases and nondisease phenotypes is of growing importance in human biology studies. In this laboratory exercise, students determine the genetic basis for their ABO blood type; however, no blood is drawn. Students isolate genomic DNA from buccal mucosa cells that are present in saliva and analyze the DNA on an agarose gel. Subsequently, this DNA is used as a PCR template to amplify exons 6 and 7 of the gene that determines the human ABO phenotype. These PCR products are digested and run on agarose gels to examine the restriction fragment length polymorphisms. A deletion in the O(1) allele converts the BstE II site in exon 6 into a Kpn I site, and this feature is used to determine the presence of O(1) alleles. The pattern of exon 7 digest products allows students to distinguish among four other common ABO alleles: A(1) , A(2) , B, and O(2) . This exercise introduces students to commonly used molecular biology techniques, such as genomic DNA isolation, PCR, gel electrophoresis, and restriction digests.

Number of B sites generated on group O red cells from adults and newborn infants

When red cells from the group O blood of adults and newborn infants (cord blood) were incubated with UDP-galactose and group B serum, over 200,000 B sites per cell were generated on adult O cells but only 40,000--70,000 sites per cell on cord cells. It is concluded that smaller amounts of substrate for the B transferase are present on cord cells.