The computer crossmatch: a safe alternative to the serological crossmatch.

The crossmatch has evolved from including a wide range of techniques through a test purely to eliminate ABO incompatibility (immediate spin) to computer crossmatching in which no serological testing is carried out and validation ensures the correct ABO/RhD type blood is issued. The crossmatch was always considered to be the most important feature of the compatibility test and in particular the antiglobulin phase; however, there are potential risks associated with serological and computer crossmatching including technical and procedural errors. The use of immediate spin and computer crossmatch change the emphasis for safety of the compatibility test from the crossmatch to the antibody screen.

Epitopes on Rh proteins.

Analyses of the reactions of monoclonal anti-D with Rh D variant red cells have shown that there are at least 24 different epitopes of the Rh D antigen. Similar studies Of Rh E variant red cells with monoclonal anti-E indicate that there are at least 4 epitopes of the Rh E antigen. The relation of these serologically defined epitopes to the structure of the Rh proteins is reviewed.

Site directed mutagenesis of the human Rh D antigen: molecular basis of D epitopes.

Previous attempts to define the molecular configuration of D epitopes has been confined to the analysis of the serological profile and Rh D molecular structure of partial D phenotypes. There are numerous drawbacks in this approach, most fundamental of which is that with the exception of RoHar, partial D phenotypes are defined by the loss of D epitope expression, and is thus difficult to directly correlate a specific amino acid to a particular D epitope. Furthermore, most partial D phenotypes are associated with multiple amino acid changes in the mutant Rh protein species associated with partial D expression.

Monoclonal antibodies to Rh D--development and uses.

Monoclonal anti-D has proved impossible to make in rodent systems. Human monoclonal anti-D has been produced using EBV transformed peripheral B cells, coupled with fusions to myeloma cell lines. More recently molecular biology techniques have been used to produce monoclonal anti-D.

Molecular configuration of Rh D epitopes as defined by site-directed mutagenesis and expression of mutant Rh constructs in K562 erythroleukemia cells.

The Rh D antigen is the most clinically important protein blood group antigen of the erythrocyte. It is expressed as a collection of at least 37 different epitopes. The external domains of the Rh D protein involved in epitope presentation have been predicted based on the analysis of variant Rh D protein structures inferred from their cDNA sequences and their D epitope expression.

International reference reagents: antihuman globulin. An ISBT/ICSH joint working party report. International Society of Blood Transfusion. International Committee for Standardization in Haematology.

An international working party has conducted a study designed to select a suitable reference reagent for antihuman globulin, to replace those first made available in 1987. The chosen preparation contains levels of anti-IgG and anti-C3 (anti-C3c and anti-C3d) potency that are considered suitable to serve for reference when evaluating either polyspecific antihuman globulin reagents or those containing their separate monospecific components. The reference material is available in 2-ml freeze-dried aliquots from seven assigned distribution centres.

Detection of weak D and D(VI) red cells in D-negative mixtures by flow cytometry: implications for feto-maternal haemorrhage quantification and D typing policies for newborns.

Quantitation of feto-maternal haemorrhage (FMH) by flow cytometry (FC) has been shown to be more accurate than the Kleihauer-Bekte test. Fetal cells will be predominately of R1r or R2r phenotype, with antigen site numbers per cell (SPC) of between 9900 and 16000. If the fetus is of weak D or partial D(VI) phenotype, fewer SPC will be present.

Site-directed mutagenesis of the human D antigen: definition of D epitopes on the sixth external domain of the D protein expressed on K562 cells.

Background: The antigens of the human Rh system are of great clinical significance in transfusion medicine and pregnancy. Of the Rh system antigens, D is clinically the most important, being one of the most immunogenic structures arising from human cells. The human D antigen represents a collection of epitopes expressed on a red cell membrane protein that is predicted to have 12 membrane-spanning segments giving rise to six exofacial domains.

New reference reagent for the quality assurance of anti-D antibody detection.

A UK BTS-NIBSC freeze-dried anti-D preparation has been prepared and used to monitor the performance of routine antibody detection tests and of the test operators. With the day-to-day use of this preparation, adverse changes in test performance and in test operator may be detected and appropriate action taken before the effect becomes significant. Two dilutions of this preparation have been defined, one which should be detected unequivocally in every test; the other, more dilute, may not be detected in every test but is used to monitor changes in performance.

IgG anti-Jka/Jkb antibodies are unlikely to fix complement.

Antibodies in the Kidd blood group system show a great deal of serological variability, are notoriously elusive and hence evoke difficulties in detection. However, they have been regularly reported as causing severe immediate or delayed haemolytic transfusion reactions and this clinical potential has been largely attributed to their complement binding ability. In initial investigations on 43 anti-Jka/Jkb sera with a range of titres of IgG antibody only a few seemed to fix complement, though following repeated tests on 20 of these sera a further five were shown to bind complement, making a total of 12 (27.

DBT: a partial D phenotype associated with the low-incidence antigen Rh32.

Eight probands are described with a D phenotype in which a partial D antigen is associated with Rh32 antigen; three of these probands were investigated because of the anti-D in their serum. The partial D lacks epD1-epD5 and epD9 and some epD6/7 and only expresses epD8 and other parts of epD6/7. The strength of the partial D antigen varies between unrelated DBT individuals.

Molecular basis of the D variant phenotypes DNU and DII allows localization of critical amino acids required for expression of Rh D epitopes epD3, 4 and 9 to the sixth external domain of the Rh D protein.

The discovery of Rh partial D variant red cells by discrepant reactions with different monoclonal anti-D has demonstrated the range of Rh D epitopes that have arisen due to alterations in Rh D protein structure. There are two current classification systems, one which uses a nine epitope model (epD1-epD9) whereas a more recent model proposes 30 different epitopes. We describe here the molecular basis of two D variants which lack epD4 and epD9 namely the DNU and D(II) phenotypes.

An explanation and the clinical significance of the failure of microcolumn tests to detect weak ABO and other antibodies.

Shear forces are proposed to explain the failure of antiglobulin and 'neutral' (no antiglobulin) microcolumn tests at 37 degrees C to detect weak ABO incompatibilities and other weak antibodies, clearly detectable by spin-tube methods. These shear forces can be minimized in a microcolumn test using a biphasic centrifugation phase. Although this biphasic test is not suitable for routine use, it may be of use as an investigational method for reference laboratories.

Molecular analysis of Rh transcripts and polypeptides from individuals expressing the DVI variant phenotype: an RHD gene deletion event does not generate All DVIccEe phenotypes.

The D antigen is a mosaic comprising at least 30 epitopes. Partial Rh D phenotypes occur when there is absence of one or more of these epitopes, with the remainder expressed. The DVI phenotype is the most common of the partial D phenotypes, lacking most D antigen epitopes (ep D) (epD1, 2, 5-8 using the 9-epitope model or epD 1-4, 7-22, 26-29 using the 30-epitope model).

The serological profile and molecular basis of a new partial D phenotype, DHR.

Background And Objectives: The Rh D antigen comprises a mosaic of at least 30 epitopes expressed on a 30-kD non-glycosylated Rh D polypeptide. The equivalent Rh CeEe polypeptide expressing the Rh C/c and E/e antigens differs in only 36 of the 417 amino acid residues. Partial D individuals have been described who fail to express a number of D epitopes.

Serologic characteristics of H-deficient phenotypes among Chinese in Hong Kong.

Background: The occasional presence of H-deficient red cells among both referred and donor blood samples prompted the mass screening of donated blood in Hong Kong for H-deficient phenotypes; 96 percent of the donors tested are Chinese from the southern province of Kwongtung.

Study Design And Methods: Donor blood was screened for H-deficient red cells with the use of Ulex europaeus. Lewis phenotyping was carried out on all H-deficient individuals, and saliva testing was performed on most such individuals.