Review: the molecular basis of the Rh blood group phenotypes.
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Antigen-Antibody Reactions↗
Biomedical subjects
F F Wagner
Publications and source records attributed to F F Wagner.
Section 1B: Rh flow cytometry. Coordinator's report. Rhesus index and antigen density: an analysis of the reproducibility of flow cytometric determination.
Fifty-seven IgG monoclonal anti-D antibodies were evaluated in the Rh flow cytometry section, in which 12 laboratories participated. Staining protocols and a fluorescein (FITC)-conjugated Fab fragment goat anti-human IgG (H + L) as a secondary antibody were recommended but not mandatory. A CcDEe red blood cell (RBC) sample that was shown to be homozygous for RHD by molecular methods was supplied and used as internal 'standard RBC' throughout all experiments. An RBC panel comprising two partial D and four weak D types was supplied as well. The use of standard RBC reduced the variability of the data among the laboratories and allowed the conversion of fluorescence data into epitope densities, which were compounded in an antigen density (antigen D per RBC). The highest antigen density was determined for DVI type III, followed by DVII and weak D type 3; the lowest antigen density were determined for weak D type 1 and type 2. Nine of the 12 participating laboratories discriminated three groups of aberrant RhD that had similar Rhesus indices (RI): D category VI with RI = 0; weak D type 2 and type 3 with an high RI; and D category VII and weak D type 1 with an intermediate RI. The antigen densities and the Rhesus indices obtained correlated well among the laboratories of this Workshop section despite different staining protocols, secondary antibodies and instrumentation.
Algorithms↗
RHD positive haplotypes in D negative Europeans.
BACKGROUND: Blood group genotyping is increasingly utilized for prenatal diagnosis and after recent transfusions, but still lacks the specificity of serology. In whites, the presence of antigen D is predicted, if two or more properly selected RHD-specific polymorphism are detected. This prediction must fail, if an antigen D negative RHD positive allele is encountered. Excluding RHDpsi and CdeS frequent only in individuals of African descent, most of these alleles are unknown and the population frequency of any such allele has not been determined. METHODS: We screened 8,442 antigen D negative blood donations by RHD PCR-SSP. RHD PCR positive samples were further characterized by RHD exon specific PCR-SSP or sequencing. The phenotype of the identified alleles was checked and their frequencies in Germans were determined. RESULTS: We detected 50 RHD positive samples. Fifteen samples harbored one of three new Del alleles. Thirty samples were due to 14 different D negative alleles, only 5 of which were previously known. Nine of the 14 alleles may have been generated by gene conversion in cis, for which we proposed a mechanism triggered by hairpin formation of chromosomal DNA. The cumulative population frequency of the 14 D negative alleles was 1:1,500. Five samples represented a D+/- chimera, a weak D and three partial D, which had been missed by routine serology; two recipients transfused with blood of the D+/- chimera donor became anti-D immunized. CONCLUSION: The results of this study allowed to devise an improved RHD genotyping strategy, the false-positive rate of which was lower than 1:10,000. The number of characterized RHD positive antigen D negative and Del alleles was more than doubled and their population frequencies in Europe were defined.
Adult↗
A new h allele detected in Europe has a missense mutationin alpha(1,2)-fucosyltransferase motif II.
BACKGROUND: The FUT1 gene encodes an alpha(1,2)-fucosyltransferase (H transferase), which determines the blood group H. Nonfunctional alleles of this gene, called h alleles and carrying loss-of-function mutations, are observed in the exceedingly rare Bombay phenotype. Twenty-three distinct h alleles have been characterized at the molecular level in various populations. The FUT2 (SE) gene is highly homologous to FUT1 (H:). STUDY DESIGN AND METHODS: The FUT1 gene of an Austrian proband with the Bombay phenotype was characterized by nucleotide sequencing of the full-length coding sequence. A PCR method using sequence-specific primers for FUT2 genotyping in whites was developed. The plasma alpha(1,2)-fucosyltransferase activity was determined. The distribution of the mutations underlying 24 h alleles and 7 se alleles was analyzed. RESULTS: The proband carried a new h allele. Two nucleotide changes, G785A and C786A, in codon 262 of the FUT1 gene resulted in the replacement of serine by lysine. No alpha(1,2)-fucosyltransferase activity was detected in the proband's plasma. The proband was homozygous for the seG428A allele. Six of 17 missense mutations in nonfunctional h and se alleles occurred in highly conserved fucosyltransferase motifs. No loss-of-function mutation was observed in the aminoterminal section encompassing the transmembraneous helix. CONCLUSION: The missense mutation S262K in the FUT1 gene caused the loss of H transferase activity. The analysis of the distribution of mutations in nonfunctional FUT1 and FUT2 genes can point to functionally important domains in the H transferase.
ABO Blood-Group System↗
PCR screening for common weak D types shows different distributions in three Central European populations.
BACKGROUND: DNA sequencing showed RHD mutations for all weak D phenotypes investigated in a study from Southwestern Germany. Molecular classification of weak D offers a more reliable basis than serotyping and is relevant for optimal D transfusion strategies. STUDY DESIGN AND METHODS: Sequence-specific primers were designed to detect weak D types 1 to 5 and the partial D phenotype HMi in a modular set for conventional PCR analysis. Alternatively, all reactions were multiplexed into a single tube, and the products were identified after automated capillary electrophoresis by their size and fluorescence. Weak D phenotype samples from 436 donors in the Tyrol (Austria) and Northern Germany were investigated by PCR. RESULTS: More than 90 percent of the weak D types identified by PCR represented type 1, 2, or 3. The distribution among the common types varied between the Tyrol and Northern Germany (p<0.0001). Three new RHD alleles were identified. CONCLUSION: A PCR method of detecting the common weak D types was validated. This PCR system introduces a simple and rapid tool for routine DNA typing of weak D samples. The results confirmed that all weak D phenotype samples identified by current serologic criteria carry altered D proteins.
Alleles↗
A D(V)-like phenotype is obliterated by A226P in the partial D DBS.
BACKGROUND: In D category V types, the RHD exon 5 or parts thereof are replaced by the corresponding RHCE DNA segments. In D category V types I and II, the amino acid at position 226 is alanine, which is typical of the prevalent RHD allele and is observed in all RHCE alleles encoding the antigen e. A proline at position 226 in RHCE encodes the antigen E. STUDY DESIGN AND METHODS: A blood sample of ccDEe phenotype was referred as suspected D category VI. The RHD nucleotide sequence and the D epitope pattern were determined. RESULTS: A new partial D, DBS, encoded by an RHD-RHcE(5)-RHD hybrid allele, was found. Although it differed from D(Va) type II by an A226P substitution only, it lacked epitopes epD4, epD12, epD17, epD18, and epD22 that were present in D(Va). The 5' breakpoint region was located between the deletion in RHD intron 4 and the first polymorphic nucleotide of DBS exon 5. CONCLUSION: The phenotypes of RHD alleles with gene conversions limited to exon 5 depended critically on the amino acid at position 226. If alanine was present at this position, gene conversions involving E233Q led to a D(Va)-like phenotype. If proline was present, many additional epitopes were lost, and the phenotype became reminiscent of DFR. The 5' breakpoint region is shared by 10 alleles and may represent the most active "hot spot" for gene conversions known in RH.
Adult↗
An AQP1 null allele in an Indian woman with Co(a-b-) phenotype and high-titer anti-Co3 associated with mild HDN.
BACKGROUND: The Colton blood group system (CO, ISBT 015) is composed of three antigens, of which Co3 (ISBT 015.003) is carried by almost all persons, except those of the extremely rare Co(a-b-) phenotype. The Colton blood group antigens are expressed by the water channel aquaporin 1 (aqp1; also known as channel-forming integral protein, CHIP-28), which is a highly conserved RBC integral membrane protein. The two most frequent alleles, CO1 and CO2, encode the antigens Co(a) and Co(b), respectively. Four null alleles have been described for the AQP1 gene to date. CASE REPORT: An Indian woman had an alloimmune antibody to an high-frequency antigen associated with mild HDN. Her RBCs were typed Co(a--b-), and the antibody was an anti-Co3. She typed CO1-positive and CO2-negative in a new genotyping method, using PCR with sequence-specific priming, for CO1 and CO2. A method for nucleotide sequencing of the four AQP1 exons from genomic DNA was developed. The patient was shown to be homozygous for a nonfunctional allele AQP1(232delG) that also carried the CO1-specific polymorphism. CONCLUSION: The kindred presented a fifth example of an AQP1 null allele, which was caused by a single nucleotide deletion leading to a shift in the reading frame beyond codon 78. A method of genotyping CO for Co(a) and Co(b) antigen phenotype prediction was presented.
Adult↗
Completely converting a national blood supply to the use of safer plasma.
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Blood Banks↗
RHD gene deletion occurred in the Rhesus box.
The Rh blood group antigens derive from 2 genes, RHD and RHCE, that are located at chromosomal position 1p34.1-1p36 (chromosome 1, short arm, region 3, band 4, subband 1, through band 6). In whites, a cde haplotype with a deletion of the whole RHD gene occurs with a frequency of approximately 40%. The relative position of the 2 RH genes and the location of the RHD deletion was previously unknown. A model has been developed for the RH locus using RHD- and RHCE-related nucleotide sequences deposited in nucleotide sequence databases along with polymerase chain reaction (PCR) and nucleotide sequencing. The open reading frames of both RH genes had opposite orientations. The 3' ends of the genes faced each other and were separated by about 30 000 base pair (bp) that contained the SMP1 gene. The RHD gene was flanked by 2 DNA segments, dubbed Rhesus boxes, with a length of approximately 9000 bp, 98.6% homology, and identical orientation. The Rhesus box contained the RHD deletion occurring within a stretch of 1463 bp of identity. PCR with sequence-specific priming (PCR-SSP) and PCR with restriction fragment length polymorphism (PCR-RFLP) were used for specific detection of the RHD deletion. The molecular structure of the RH gene locus explains the mechanisms for generating RHD/RHCE hybrid alleles and the RHD deletion. Specific detection of the RHD(-) genotype is now possible. (Blood. 2000;95:3662-3668)
Base Sequence↗
Weak D alleles express distinct phenotypes.
The weak D phenotype is caused by many different RHD alleles encoding aberrant RhD proteins, raising the possibility of distinct serologic phenotypes and of anti-D immunizations in weak D. We reported 6 new RHD alleles, D category III type IV, DIM, and the weak D types 4.1, 4.2.1, 4.2.2, and 17. The immunohematologic features of 18 weak D types were examined by agglutination and flow cytometry with more than 50 monoclonal anti-D. The agglutination patterns of the partial D phenotypes DIM, D(III) type IV, and D(IV) type III correlated well with the D epitope models, those of the weak D types showed no correlation. In flow cytometry, the weak D types displayed type-specific antigen densities between 70 and 4000 RhD antigens per cell and qualitatively distinct D antigens. A Rhesus D similarity index was devised to characterize the extent of qualitative changes in aberrant D antigens and discriminated normal D from all tested partial D, including D category III. In some rare weak D types, the extent of the alterations was comparable to that found in partial Ds that were prone to anti-D immunization. Four of 6 case reports with anti-D in weak D represented auto-anti-D. We concluded that, in contrast to previous assumptions, most weak D types, including prevalent ones, carry altered D antigens. These observations are suggestive of a clinically relevant potential for anti-D immunizations in some, but not in the prevalent weak D types, and were used to derive an improved transfusion strategy in weak D patients. (Blood. 2000;95:2699-2708)
Alleles↗
Predicting a donor's likelihood of donating within a preselected time interval.
The procurement of some advanced blood components, like quarantined plasma units, depends critically on retesting the donor within a fixed time frame. For health care systems, such as that in Germany, with mandatory retesting of donors before plasma release, the reliable identification of donors who are more likely to return in time has an immense practical implication, because their blood components could be preferably selected for quarantine purposes. The donation histories of about 760 000 donors with 4910 000 donation attempts were analysed. We developed a logistic regression model to calculate a probability of donation, p(Dts-te), within a preselected time frame (ts-te). The donation history was compounded in a score and shown to be very useful for determining p(Dts-te). A logistic regression model was developed with score and donor status as parameters; different regression coefficients applied to first-time-donors (ftd) and to repeat donors (intercept, int, and score factor, scf ). This model allowed us to determine the probability of donation, p(Dts-te), within a preselected time interval, e.g. 6-9 months after an index donation. The p(Dts-te) can be calculated for any donor of blood services. The p(D170-275 days) ranged from about 22% to 86% for any index donation in 1996/97. First-time donors had a p(D170-275 days) of 33% and were more likely to return within the time interval than certain subsets of repeat donors who can be defined by our model. We provided a technical procedure to increase the rate of plasma unit release after quarantine storage and showed the usefulness of our procedure for blood component management, if quarantine storage is required. By applying the model to our current plasma quarantine programme we could retrieve about 30% more units, which would represent about 30 000 units per year, without incurring additional costs. General implications for blood collection, like planning blood drives, were discussed. The whole demand of a health care system for single plasma units may be met by quarantine plasma and their cost-efficiency can be improved.
Adolescent↗
Primary anti-D immunization by weak D type 2 RBCs.
BACKGROUND: D is the most immunogenic blood group antigen. In about 0.4 percent of whites, D is expressed on RBCs in a weak form. Recently, it was found that the weak D phenotypes are caused by a large number of distinct RHD alleles generally encoding altered D proteins. No particular molecular weak D type has yet been shown to induce anti-D. The threshold of D antigen density required for anti-D immunization is not known. CASE REPORT: A 72-year-old D- white man received apparently D- RBCs. Nineteen days later, he developed a positive DAT, and anti-D was found in his serum and an eluate from his RBCs. One donor was found to be D+ with a weak D type. The weak D type was determined by RHD exon 9-specific nucleotide sequencing from genomic DNA. The transfusion recipient showed alloanti-D. Ten months later, anti-D but no other antibody was detectable; the DAT was negative and the eluate was nonreactive. The donor of the incriminated unit was D+ (ccDEe) with weak D due to the weak D type 2 allele, expressing about 450 D antigens per RBC. CONCLUSION: This case provides formal proof that RBCs of weak D type 2 phenotype may cause alloanti-D immunization. Among the more prevalent weak D types in whites, weak D type 2 has the lowest D antigen density. Thus, units of blood from donors of the weak D type 2 phenotype should be labeled D+; the weak D type 2 phenotype may be useful for quality assurance.
Aged↗
Molecular genetics of RH.
BACKGROUND AND OBJECTIVES: The two Rhesus proteins, RhD and RhCE, constitute one of the clinically most relevant blood group antigen system. In the last two years, the understanding of RH molecular genetics has increased considerably. The state of the current knowledge was briefly summarised. MATERIALS AND METHODS: Recent reviews, original work since 1999 and own results were utilised. RESULTS: The structure of the RH gene locus comprising RHD, RHCE and SMP1 was presented. True RHD genotyping became feasible by establishing the molecular basis of the most prevalent RH haplotype in whites harbouring the RHD gene deletion and of the RHD pseudogene RHD psi in Africans. Molecular and serologic characteristics of weak D and partial D alleles were compared. Closely related alleles for both, weak D and partial D, were collated as examples contributing to the understanding of RH phylogeny. CONCLUSION: The RH gene locus is a model system for molecular polymorphism in clustered genes and suitable for studying molecular evolution in humans. It lends itself for developing molecular diagnostics because its genetics is appropriately complex and challenging; yet the expressed phenotypes have been studied for decades and are well understood. Legal and ethical issues that are rightfully of public concern would not be infringed if RH genotyping will be attempted on a massive scale.
Alleles↗
Molecular basis of weak D phenotypes.
A Rhesus D (RhD) red blood cell phenotype with a weak expression of the D antigen occurs in 0.2% to 1% of whites and is called weak D, formerly Du. Red blood cells of weak D phenotype have a much reduced number of presumably complete D antigens that were repeatedly reported to carry the amino acid sequence of the regular RhD protein. The molecular cause of weak D was unknown. To evaluate the molecular cause of weak D, we devised a method to sequence all 10 RHD exons. Among weak D samples, we found a total of 16 different molecular weak D types plus two alleles characteristic of partial D. The amino acid substitutions of weak D types were located in intracellular and transmembraneous protein segments and clustered in four regions of the protein (amino acid positions 2 to 13, around 149, 179 to 225, and 267 to 397). Based on sequencing, polymerase chain reaction-restriction fragment length polymorphism and polymerase chain reaction using sequence-specific priming, none of 161 weak D samples investigated showed a normal RHD exon sequence. We concluded, that in contrast to the current published dogma most, if not all, weak D phenotypes carry altered RhD proteins, suggesting a causal relationship. Our results showed means to specifically detect and to classify weak D. The genotyping of weak D may guide Rhesus negative transfusion policy for such molecular weak D types that were prone to develop anti-D.
Alleles↗
Three molecular structures cause rhesus D category VI phenotypes with distinct immunohematologic features.
Rhesus D category VI (DVI) is the clinically most important partial D. DVI red blood cells were assumed to possess very low RhD antigen density and to be caused by two RHD-CE-D hybrid alleles. Because there was no population-based work-up, we screened three populations in central Europe for DVI. Twenty-six DVI samples were detected and examined by exon-specific RHD polymerase chain reaction with sequence-specific primers (PCR-SSP). A new genotype, hereby designated D category VI type III, was characterized as a RHD-Ce(3-6)-D hybrid allele by sequencing of the cDNA, parts of intron 1, and by PCR-restriction fragment length polymorphism (PCR-RFLP) of intron 2. Rhesus introns 5 and 6 were sequenced and the 3' breakpoints of all known DVI types shown to be distinct. We differentiated the 5' breakpoints of DVI type I and DVI type II by a newly devised RHD-PCR. Thus, the DVI phenotype originated in at least three independent molecular events. Each DVI type showed distinct immunohematologic features in flow cytometry. The number of RhD proteins accessible on the red blood cells' surface of DVI type III was normal (about 12,000 antigens/cell; DVI type I, 500; DVI type II, 2,400) based on the determination of an RhD epitope density profile. DVI type II and DVI type III occurred as CDe haplotypes, and DVI type I as a cDE haplotype. The distribution of the DVI types varied significantly in three German-speaking populations. Genotyping strategies should take account of allelic variations in partial RhD. The reconsideration of previous serologic and clinical data for partial D in view of the underlying molecular structures may be worthwhile.
Alleles↗
Rh phenotype prediction by DNA typing and its application to practice.
The complexity of the RHD and RHCE genes, which is the greatest of all blood group systems, confounds analysis at the molecular level. RH DNA typing was introduced in 1993 and has been applied to prenatal testing. PCR-SSP analysis covering multiple polymorphisms was recently introduced for the screening and initial characterization of partial D. Our objective is to summarize the accrued knowledge relevant to the approaches to Rh phenotype prediction by DNA typing, their possible applications beyond research laboratories and their limitations. The procedures, results and problems encountered are highly detailed. It is recommended that DNA typing comprises an analysis of more than one polymorphism. We discuss future directions and propose a piecemeal approach to improve reliability and cost-efficiency of blood group genotyping that may eventually replace the prevalent serology-based techniques even for many routine tasks. Transfusion medicine is in the unique position of being able to utilize the most extensive phenotype databases available to check and develop genotyping strategies.
Blood Transfusion↗
Blood transfusion: influence of transfusion therapy on outcome.
Few studies have addressed the influence of different transfusion therapies on outcome in a convincing way. Proven adverse impact of allogeneic blood on outcome is minimal. Acute mortality has declined to about 1 : 500,000 and the rate of transfusion-transmitted infections is decreasing, too. Data on postoperative infections and non-Hodgkin's lymphoma as possible adverse effects are controversial. Evidence for an increased risk of tumour recurrences is lacking. Alternatives to allogeneic blood may have appreciable risks: perioperative blood recovery had a fatality rate of more than 1 : 40,000. Reduction of allogeneic blood exposure may not be equated with improved outcome.
Journal Article↗
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. These would have both been originally classified as D(II) phenotype individuals, but we have revealed subtle differences in the serological profile of these erythrocytes. Such a differential reactivity and determination of the molecular bases of these phenotypes allows us to predict critical amino acids for epD3, epD4 and epD9 expression. The DNU phenotype arises from a single point mutation in the RHD gene resulting in a single amino acid change (Gly353Arg). Sequence analysis of exon 7 of the RHD gene derived from the D(II) propositus indicates that there is a single point mutation in this exon resulting in a single amino acid change (Ala354Asp). It is likely that this point mutation gives rise to the D(II) phenotype. Both mutations result in the change to Rh D-specific residues. Our results indicate that the following amino acids are crucial for epD3a (Asp350), epD3b (Asp350 + Gly353), epD4a (Gly353 + Ala354), epD4b (Ala354), epD9a (Asp350 + Gly353 + Ala354) and epD9b (Asp350 + Ala354) expression. All of these amino acids reside on the predicted sixth external domain of the Rh D protein, so it is possible that epD3, 4 and 9 are continuous epitopes.
Amino Acids↗