Red Cell D Antigen Sites and Titration Scores in a Family with Weak and Normal D<sup>u</sup> Phenotypes Inherited from a Homozygous D<sup>u</sup> Mother

Measurements have been made of the number of available sites on 10 examples of red cells in which the only abnormality appeared to be a quantitative reduction in the expression of D (weak D cells); these estimates were carried out using three monoclonal anti-D antibodies, Fog-1, Brad-3 and Los-2. The values varied with the monoclonal antibody that was used and fell within the range of 170-1,870 sites/cell. A further 3 examples of weak D cells which had brought about immunisation following transfusion were found to have between 390 and 1,470 sites per red cell. The implications of the D site density on the immunogenicity of weak D cells are discussed. The number of sites on red cells with structurally abnormal D (partial D cells) were also estimated, using the antibody Fog-1. Four of the 5 examples of cells of category IVa (probable phenotype R(0)r) were found to have a high expression of D (range 29,300- 41,300), but the available D sites of categories D^Va, D^VIa, and D^VII were considerably reduced (<500, <500 and 2,400-7,500 sites/cell, respectively). As a working hypothesis, it is suggested that there are two types of genetic abnormality leading to an abnormal expression of D. First, a defect in genomic DNA leading only to a quantitative reduction in the number of available D sites; this genomic lesion should be termed ‘weak D’. Secondly, genomic defects leading to amino acid sequence abnormalities and structural change in the D polypeptide; these lesions should be collectively known as ‘partial D’.

Section: Resultssupporting

confidence: 68%

“…The first report was by Bush et al [5] who studied 7 people all belonging to the same family; thus all the abnormalities resulted from the presence of the same abnormal gene. The number of sites ranged between 110 and 540 per red cell.…”

Section: Introductionmentioning

confidence: 99%

Quantitation of D Sites on Selected 'Weak D' and 'Partial D' Red Cells

Gorick¹,

McDougall²,

Ouwehand³

et al. 1993

“…One situation in which the use of IgM anti-D in red cell phenotyping can be problematic is the detection of weak D cells expressing low amounts of RhD sites per cell [5]. The relative low reactivity of IgM-containing anti-D reagents with these cells is probably related to the low intrinsic affinity of the IgM monomeric units (compared to IgG) [6].…”

Section: Introductionmentioning

confidence: 99%

Direct Agglutination of Weak D Red Cells by Tetramolecular Complexes Containing Monoclonal IgG Anti-D

Lemieux¹,

Verrette²,

Broly³

et al. 1993

The capacity of blood group antibodies to agglutinate red cells suspended in saline is largely dependent on the antibody isotype. The immunological cross- linking of IgG antibodies has previously been described as a means to increase the reactivity of IgG in many situations. We have prepared anti-D-containing complexes by blending a human IgG anti-D monoclonal antibody (mAb) and a murine anti-human IgG mAb. In standard red cell serology assays, the anti-D complexes exhibited a very high avidity and could agglutinate weak D-positive red cells in direct saline testing. These results indicate that potent saline hemagglutinating reagents of RhD and eventually of other blood group specificities can be prepared from IgG mAbs.

“…These results are somewhat less than those presented in this paper. How ever, all the samples of Bush et al [1] are taken from one family, whereas those in this study are taken from random blood donors.…”

Section: Discussionmentioning

confidence: 99%

“…Bush et al [1] presented data from a family study concerned with Du pheno types. Using 125I-labelled anti-D they cal culated the average number of sites per Du cell to be 300 with a range of 110-540.…”

Section: Discussionmentioning

confidence: 99%

A Study of Different Rhesus Phenotypes and their Binding Characteristics

Morley¹

1978

A method has been developed using the AutoAnalyzer to study the binding characteristics of anti-D with cells of various rhesus phenotypes. A positive association has been demonstrated between site density and association constant. A hypothesis is proposed for the presence of two types of antigenic sites on the cell surface recognised only by affinity differences. The higher affinity site binds both arms of an IgG anti-D molecule, whereas the lower affinity site binds only one.