The genomic organization of the partial D category DVa: the presence of a new partial D associated with the DVa phenotype

Transfusion support for a patient with alloanti-D and the RHD*DV.1 allele

BACKGROUND

Safe blood transfusion is significantly affected by the complex antigen polymorphism and a high proportion of autoantibodies of the Rh blood group system.

THE PATIENT AND METHODS

A male Chinese patient with primary biliary cirrhosis, esophageal and gastric rupture, and bleeding was admitted to our hospital. Blood typing identified that he had serological O and D+ blood groups. Because autoantibody was not detected using routine immediate spin (IS) and indirect antiglobulin test (IAT), he was treated by transfusing D+ red blood cells (RBCs). However, this treatment was ineffective. Thus, manual polybrene test (MPT) and low ionic salt solution indirect antiglobulin test (LISS-IAT) were performed, followed by exon sequencing of the RHD gene.

RESULTS

The patient was confirmed as a DV Type 1 individual by gene sequencing, and had 4+ RhD antigen agglutination. The anti-D in serum and elution could only be detected by MPT (2+ agglutination) and LISS-IAT methods (1+/3+ agglutination). It was presumed that attenuated alloantibody contributed to ineffective RBC transfusion, causing a transient increase in hemoglobin (HGB) before falling back to 50 g/L or even lower within four days.

CONCLUSION

Genotyping helps to support the specificity of detecting autoantibodies and alloantibodies. Combining more serological methods with molecular technology in blood typing is beneficial to improve the safety and effectiveness of blood transfusion.

Frequency of RHD variants in serologically weak D Turkish blood donors

BACKGROUND

RhD typing has remained of primary importance, as being the leading cause of hemolytic disease of the newborn. Among Rh system's 55 blood group antigens, RhD is the most immunogenic. We aimed with this study to determine weak D/partial D variant frequency in blood donors who were admitted to our blood center and have serologically designated blood group weak D.

MATERIALS AND METHODS

We screened blood donors who admitted between 2011 and 2017 to our blood center. Sixty-seven serologically weak D phenotyped donors have participated in the study. These donors' samples were studied further by Polymerase Chain Reaction Sequence- Specific Primers (PCR-SSP) for determining D variants.

RESULTS

Weak D phenotype was detected in 228(0.12 %) out of 177,554 donors. Sixty-seven of them agreed to take part in the study. The frequency of weak D and partial D was 68.7 % (n = 46), and 22.4 % (n = 15), in order. The most encountered weak D and partial D variant was type 15 and DFR type, respectively.

CONCLUSIONS

The prevalence of serologically weak D phenotypes varies by race and ethnicity. Turkey is a country covering a mixture of European and Asian DNA with different ethnic groups. Thus, our research as giving the overall distribution of RHD variants from the largest city of Turkey, which may reflect the general ethnic background of the country, would help to the establishment of a databank for blood banking. This paper is the first molecular study on RHD variants in Turkey. New molecular research would be more reliable and precise.

Comprehensive Molecular Analysis of Serologically D-Negative and Weak/Partial D Phenotype in Thai Blood Donors

Background

Molecular genetics of the Rh system has been extensively studied in Caucasians, Black Africans, East Asians, and Indians more recently. In this work, we sought to investigate the molecular basis of variant D expression in the Thai population, which remains unknown.

Materials and Methods

Blood samples from 450 Thai donors showing the variant D phenotype were collected. The RHD gene was analyzed by quantitative multiplex polymerase chain reaction of short fluorescent fragments and/or Sanger sequencing.

Results

The most frequent alleles in 200 D-negative and 121 DEL samples were the whole RHD gene deletion and the Asian DEL alleles, respectively. In 129 weak/partial D samples, 36 variant alleles were identified, including eight novel alleles. RHD*06.03, which is common in variant D samples from South China, is the most prevalent variant allele, followed by the recently reported Indian RHD*01W.150 allele.

Discussion

For the first time, a comprehensive overview of the nature and distribution of variant RHD alleles in Thailand is reported. It is a milestone to pave the way towards improvement of the current screening strategy to identify DEL donors accurately. The next step will be the design and implementation of a simple molecular test for screening the most frequent alleles, specifically in this population.

A comprehensive investigation of RHD polymorphisms in the Chinese Han population in Xi'an

BACKGROUND

This study is a comprehensive analysis of RHD in D-negative phenotypes in saline, in Xi'an, Shanxi province, central China.

MATERIAL AND METHODS

DCcEe in saline was measured for each blood sample from every donor between January 2008 and June 2012 in the Xi'an Blood Centre, China. D-negative results were confirmed by an indirect antiglobulin test and further investigated by adsorption-elution as required. The initial step of molecular analysis was RHD zygosity testing. Then RHD was detected by a sequence-specific polymerase chain reaction system for RHD(1227G>A), weak D type 15, and RHD(711delC) alleles for the samples carrying at least one RHD. For the remaining non-identified samples, ten RHD exons were amplified using a previously widely used RHD coding region sequencing method. Some RHD/RHCE conversion alleles were identified while those remaining were submitted to direct sequencing.

RESULTS

Overall, 2,493 D-negative samples in saline were detected in a total of 890,403 donors (D-negative rate, 0.28%). Among the D-negative individuals, RHD deletion (d/d) was assessed in 1685 donors (67.59%). Non-functional RHD alleles were detected in 184 donors (7.38%), the most common being the RHD-CE(2-9)-RHD and RHD(711delC) alleles. Two new alleles were observed and family investigations were performed; RHD(1227G>A) DEL was detected in 516 individuals (20.70%), and weak D or partial D variants were identified in 108 donors (4.33%). The most common alleles were weak D type 15, D(VI) type 3 and D(V) type 2. Four new weak D alleles were noted, and two cases of RHD(1227G>A)/weak D type 15 heterozygosity were confirmed.

CONCLUSIONS

Currently, it seems to be difficult to observe any new RHD alleles in the Han Chinese population. D prediction in this population is easier because popular alleles are dominant, accounting for about 99.80% of alleles in D-negative people. Weak D types and partial D variants are rare and occur in approximately 0.01% of the population.

A convenient qualitative and quantitative method to investigate RHD-RHCE hybrid genes

BACKGROUND

Molecular biology techniques, such as single specific-primer polymerase chain reaction (PCR), denaturing-high performance liquid chromatography, direct sequencing, next-generation sequencing, and microarray platforms, contribute to the efficient genotyping of the human blood group RHD gene. However, some alleles remain undetermined in rare cases in DNA samples carrying two copies of the RHD gene, which challenge the identification of D-CE hybrid genes.

STUDY DESIGN AND METHODS

We set up, in a single-tube format, a qualitative and quantitative assay based on multiplex PCR of short fluorescent fragments (QMPSF) to simultaneously amplify all 10 RHD exons on the one hand and all 10 RHCE exons on the other hand.

RESULTS

The test proved to be useful to rapidly identify hybrid genes in hemizygous RHD samples carrying a hybrid D-CE gene and to resolve unknown genotypes by quantifying individual exons in compound heterozygous samples, but also unexpectedly helped to redefine the RHDΨ haplotype. While validating the test, two novel single-point variants, c.648G>C (p.L216F) and c.1048G>C (p.D350H), were found.

CONCLUSION

For the first time, a QMPSF-based method is reliable to individually quantify the exons of both RH genes, including hybrid D-CE genes in compound heterozygous samples and may help to investigate samples with unknown RHD and/or RHCE status.

Molecular genetic blood group typing by the use of PCR-SSP technique

BACKGROUND

DNA-based methods are useful for enhancing immunohematology typings. Ready-to-use Conformité Européenne (CE)-marked test kits based on polymerase chain reaction with sequence-specific priming (PCR-SSP) have been developed, which enable the examination of weak, unexpected, or unclear serologic findings. DEVELOPMENT AND VALIDATION: Primers were designed according to established mutation databases. Proficiency testing for CE marking was performed in accordance with Directive 98/79EC of the European Parliament and of the Council of October 27, 1998 on in vitro diagnostic medical devices using pretyped in-house and external samples. INTENDED USE: BAGene PCR-SSP kits are in vitro diagnostic devices. Genotyping of ABO and RHD/RHCE as well as HPA and KEL, JK, and FY specificities has to be performed after the conclusion of the serologic determination.

APPLICATION

Ready-to-use PCR-SSP typing kits allow the determination of common, rare, or weak alleles of the ABO blood group, Rhesus, and Kell/Kidd/Duffy systems as well as alleles of the human platelet antigens.

RESULTS

The investigations showed clear-cut results in accordance with serology or molecular genetic pretyping.

CONCLUSION

PCR-SSP is a helpful supplementary technique for resolving most of the common problems caused by discrepant or doubtful serologic results, and it is an easy-to-handle robust method. Questionable cases in donor, recipient, and patient typing can be examined with acceptable cost.

Molecular basis of D variants in Chinese persons

BACKGROUND

Most studies of the molecular basis of D variants have been conducted in Caucasian and African populations. There are limited data on the molecular basis for D variants in Chinese populations.

STUDY DESIGN AND METHODS

With a blended monoclonal anti-D and a sequential slide and tube typing protocol, red blood cells from greater than 99 percent of Han Chinese were tested for the D antigen. Samples that agglutinated weakly by tube method or that reacted only by indirect antiglobulin test (IAT) were classified as D variants. The D variant was tested by an RHD polymerase chain reaction with sequence specific primers and by gene sequencing to distinguish and characterize weak D and partial D alleles.

RESULTS

Of 305,572 samples from individual donations (305,475 [99.97%] were ethnic Han and 97 [0.032%] were ethnic minorities), 304,134 (99.53%) typed as D+. Five (0.0016%) typed as D variants (weak agglutination by tube). By IAT an additional 32 (0.0105%) typed as D variants and 1401 (0.46%) typed as D-. Weak D type 15 and RHD(K409K) alleles represented 72.7 percent of all weak D phenotypes. All partial D phenotypes were DVI Type 3 or DV. Three new weak D alleles carrying 594A>T and 602C>G (weak D Type 51), 92T>C (weak D type 52), and 740T>G (weak D type 53) mutations, respectively, were identified.

CONCLUSION

There are significant differences in the frequencies and molecular characteristics of D variants among indigenous Chinese populations, compared to Caucasian and African populations, which must be considered when developing clinical practices related to D variant blood donors, transfusion recipients, or obstetrical patients.

Partial D, weak D types, and novel RHD alleles among 33,864 multiethnic patients: implications for anti-D alloimmunization and prevention

BACKGROUND

The D antigen includes category D, partial D, and weak D types, which are important because anti-D alloimmunization can occur in some but not all persons that express a variant RHD allele. At present, there is little prospective information on the prevalence of D variants among obstetric patients and potential transfusion recipients.

STUDY DESIGN AND METHODS

The RHD alleles were prospectively examined in a large patient population identified on the basis of a difference in anti-D reactivity between two reagents.

RESULTS

Fifty-five discrepancies (0.96% of D-) were noted among 33,864 ethnically diverse patients over 18 months, of which 54 represented mutated RHD alleles. Seven obstetric patients were assigned D- status based on serology; only 1 patient had a partial RHD allele. Ten of 25 (36%) obstetric patients and 4 of 6 (67%) female potential transfusion recipients of childbearing age or younger were assigned D+ status, and they expressed a D variant known to permit anti-D alloimmunization. In total 20 RHD alleles were identified including category, DVa or DVa-like alleles (n = 7), DAR (n = 8), and four novel RHD alleles including two new DAU alleles.

CONCLUSION

Given the complexity of D antigen expression, it is concluded that some clinically important D variants identified by standard serologic analysis phenotype as D+ and are potentially at risk for the development of anti-D.

Random survey for RHD alleles among D+ European persons

BACKGROUND

RHD alleles are considered more variable in African persons than in European persons. A systematic survey, however, was lacking among D+ European persons at the molecular level, precluding any definite frequency estimate.

STUDY DESIGN AND METHODS

A random survey was performed among 500 ccDee, 250 CcDee, and 250 ccDEe blood donors in southwestern Germany. They were tested by polymerase chain reaction with sequence-specific priming (PCR-SSP) for up to 12 single-nucleotide polymorphisms representative for the most frequent RHD alleles among European persons. The RHD exon 5 nucleotide sequence was also tested in all 1000 samples. The nucleotide sequence of the 10 RHD exons was checked in all samples with aberrant exon 5 or positive PCR-SSP procedures.

RESULTS

By PCR-SSP, 15 aberrant RHD alleles were found among the 500 ccDee, 2 among the 250 CcDee, and none among the ccDEe samples. One of these was the novel RHD(F223V, E233Q, T379M) allele dubbed DAU-5. Weak D type 4 was detected more frequently than expected, whereas the population frequencies of the other RHD alleles conformed to published estimates. Nucleotide sequencing of RHD exon 5 further revealed three novel alleles RHD(G212G), RHD(R234W), and RHD(V245L), dubbed DUC-1, DQC, and DUC-2.

CONCLUSION

In a limited screen at the molecular level among 1000 random D+ donors in southwestern Germany, 20 donors were found carrying aberrant RHD alleles. Four of these alleles were new and likely sporadic. An estimate was derived of the variety that may be encountered in genotyping approaches, and it was concluded that even within the European population the variety of RHD alleles may be larger than anticipated.

Whole exon 5 and intron 5 replaced by RHCE in DVa(Hus)

The DVa(Hus) was previously investigated through cDNA analysis, which revealed an RHD-CE(5)-D hybrid allele. However, the 5' and 3' breakpoints remain unknown. In this article, gene recombinations between the RHD and RHCE alleles were investigated by a combination approach of a sequence-specific primer PCR (PCR-SSP) and an RHD full-length coding region sequencing method on two Chinese subjects with weak D phenotypes. The hybrid Rhesus box of each individual was also investigated through an established PCR-based method. As a result, two partial D phenotypes, DVa(Hus) and DVI type III, were identified, each carrying one hybrid RHD-CE-D allele. The two samples were also serotyped with Rh phontypes of DccEe and DCcee, respectively. Other sequencing analyses of the DVaHus sample showed that the sequence of intron 4 is identical with RHD, whereas the whole sequence of exon 5 and intron 5 is identical with RHCE except for seven polymorphisms in the intron 5. We may concluded that in the case of this Chinese DVa(Hus), the whole exon 5 and complete intron 5 of a total segment of 1801 nucleotides were replaced by RHCE suggesting that the breakpoints of the replaced region are the 5' end of the exon 5 and the 3' end of the intron 5.

Serological studies of monoclonal RH antibodies with RH1 (D), RH2 (C), RH3 (E) and RH5 (e) variant RBCs

One hundred and forty five Mabs against RH antigens were tested. In this paper, we chose to detail reactivity of MoAbs directed against variant RBCs of the CNRGS collection for which we studied the molecular background. Because we developed procedures to identify variants of the RhD, RhC, RhE and Rhe antigens, we were especially interested in finding new monoclonal antibodies that could help us to characterize more accurately these variants. Therefore, we drew parallels between our procedures and results obtained with the 2001 workshop antibodies.

The nature of diversity and diversification at the ABO locus

In this study we analyzed the complete genomic sequences, except intron 1, and 2 regulatory regions of 6 common (ABO*A101, ABO*A201, ABO*B101, ABO*O01, ABO*O02, and ABO*O03) and 18 rare ABO alleles, 3 of which were new. This was done by phylogenetic analysis and correlating sequence data with the ABO phenotypes. The study revealed multiple polymorphisms in noncoding regions. The intron-based phylogenetic analysis revealed 5 main lineages: ABO*A, ABO*B, ABO*O01, ABO*O02, and ABO*O03. The genomic sequences of most rare ABO alleles differed slightly from those of the common alleles. Singular mutations or hybrid alleles were most common, but a few exhibited mosaic sequence pattern containing multiple exon and/or intron motifs from other ABO lineages. Thus, both an accumulation of mutations as well as an assortment of the mutations by recombination seems to be responsible for the ABO gene diversity. The prevalence of replacement mutations indicates positive selection for allelic diversity. Phenotype-genotype correlation showed that sequence variations within the complete coding sequence can affect A- and B-antigen expression. All variant ABO*A/B alleles and one new ABO*O03-like allele were associated with weak ABO phenotypes. These findings are suggestive of the requirement of a comprehensive coding sequence database for sequence-based phenotype prediction.

The evolution and formation of RH genes

The Rh system clinically is one of the important blood groups. The major Rh antigens, which are constituted by over 40 types, are RhD, RhC/c, and RhE/e. Furthermore, Rh blood group system is characterized by the existence of many variants. It was considered that Rh blood group system was encoded on two genes termed the RHCE and RHD, which are composed of ten exons, respectively. It is inferred that the RHD gene encodes the RhD antigen and that the RHCE gene encodes the Rh C/c and RhE/e antigens. There are RHce, RHCe, RHcE and RHCE alleles as polymorphisms of RHCE gene. In 2000, the entire nucleotide sequences in all introns of both the RHD and RHCE genes were determined. Due to the new findings on RH genes, it is thought that multiple recombination (and/or gene conversion), nucleotide substitutions, small nucleotide gaps, replication slippage of microsatellite, large nucleotide gaps (due to Alu sequence) and the high level of the homology (%) between both RH genes are the important factors in the formation and evolution of both RH genes and Rh variants. Based on the advance of human genome project, the new interpretations on the evolution and formation of RH genes and Rh variants will be performed. Human Rh family (superfamily) and its counterparts in primates, mammals, fish, amphibians, bacteria, lower eukaryotes, archaea and plants have been identified. A lot of findings have been accumulated in their evolution and function. As gene conversions or recombination events confuse the phylogenetic tree of human RH genes and their counterparts, careful attention is necessary for researchers to calculate the time of gene duplication and to discuss the evolution of Rh family and its counterparts.Rh genotyping methods will never be perfect and both the clinicians and researchers have to recognize the limitation of Rh genotyping, especially RhD genotyping, because new Rh variants must have formed continually. In applying the Rh genotyping to clinical medicine, especially transfusion medicine, it is necessary to compare and examine the serological (phenotypic) data in Rh blood group system with caution.

The DAU allele cluster of the RHD gene

Variant D occurs frequently in Africans. However, considerably less RHD alleles have been described in this population compared with Europeans. We characterized 5 new RHD alleles, dubbed DAU-0 to DAU-4, that shared a T379M substitution and occurred in a cDe haplotype. DAU-1 to DAU-4 were detected in Africans with partial D phenotypes. They harbored one and 2 additional missense mutations, respectively, dispersed throughout the RhD protein. An anti-D immunization was found in DAU-3. DAU-0 carrying T379M only was detected by screening European blood donors and expressed a normal D phenotype. Within the phylogeny of the RHD alleles, DAU formed an independent allele cluster, separate from the DIVa, weak D type 4, and Eurasian D clusters. The characterization of the RH phylogeny provided a framework for future studies on RH alleles. The identification of the DAU alleles increased the number of known partial D alleles in Africans considerably. DAU alleles may be a major cause of antigen D variability and anti-D immunization in patients of African descent.

Isolation, characterization, and family study of DTI, a novel partial D phenotype affecting the fourth external loop of D polypeptides

BACKGROUND

The Rh system is the most polymorphic of the blood group systems and is of major importance in transfusion medicine. The partial D phenotypes lack one or more of the D epitopes. These variants appear to have arisen through hybrid RhD-CE-D or by spontaneous point mutations in RhD. The serologic findings and the molecular characterization of a novel partial D phenotype, termed DTI, are presented here.

STUDY DESIGN AND METHODS

RBCs from the DTI proband and RBCs from individuals with other partial D phenotypes were tested with MoAbs against 16 D epi- topes, according to the recommendations of the 4th ISBT Workshop on MoAbs (Rh Section 1A). A full-length cDNA encoding DTI and introns 4 and 5 of RhD were isolated and analyzed by DNA sequencing. A family study of the DTI allele was carried out using PCR-RFLP and long-range PCR methods.

RESULTS

Analysis of RBCs from the proband revealed that the DTI phenotype lacks epitopes D1, D2.1 (partial), D2.2, D5, D6 (partial), and D8. The DTI polypeptide exhibits seven amino acid substitutions in the D polypeptide: F223V, A226P, E233Q, V238M, V245L, G263R, and K267M. The genomic organization of DTI showed that the replacement of RhD with RhCE was located in intron 4, and the replacement of RhCE with RhD was located in intron 5. Family studies revealed that the DTI allele was inherited maternally, whereas the RhD- allele was inherited paternally in the proband.

CONCLUSION

The serologic data provide the first molecular characterization of DTI, a previously unknown partial D phenotype. This phenotype affected the D polypeptide within the fourth external loop, resulting in a new RhD-CE (entire exon 5)-D hybrid gene. It is worth noting that P226, encoded by exon 5, is derived from E of RhCE in the DTI polypeptide. Family studies demonstrated that DTI was associated with a cDTIE haplotype.

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.

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.

Molecular biology and genetics of the Rh blood group system

The Rh (Rhesus) blood group system is the most complex of the known human blood group polymorphisms. The expression of its antigens is controlled by a two-component genetic system consisting of RH and RHAG loci, which encode Rh30 polypeptides and Rh50 glycoprotein, respectively. Over the past decade, there has been a rapid advance in knowledge of the biochemistry, molecular biology, and genetics of the Rh genes and proteins. The primary structures of D and CcEe antigens have become well understood and the molecular genetic basis of a vast array of phenotype polymorphisms has been delineated. The identification of various molecular defects associated with Rh deficiency syndrome clarifies the nature of the amorph, suppressor, and modifier genes. The observed mutation spectrum defines a basic set of components essential for Rh complex assembly in the erythrocyte membrane. The resulting molecular information, combined with new experimental tools, is helping to dissect the fine structure of Rh antigens in terms of epitope mapping. The discovery of novel Rh homologs in primitive organisms and in nonerythroid tissues opens new avenues of research beyond the scope of erythrocytes and Rh antigens. This review provides an update on the Rh family in antigen expression, phenotype diversity, and disease association.

The Rh blood group system: a review

The Rh blood group system is one of the most polymorphic and immunogenic systems known in humans. In the past decade, intense investigation has yielded considerable knowledge of the molecular background of this system. The genes encoding 2 distinct Rh proteins that carry C or c together with either E or e antigens, and the D antigen, have been cloned, and the molecular bases of many of the antigens and of the phenotypes have been determined. A related protein, the Rh glycoprotein is essential for assembly of the Rh protein complex in the erythrocyte membrane and for expression of Rh antigens. The purpose of this review is to provide an overview of several aspects of the Rh blood group system, including the confusing terminology, progress in molecular understanding, and how this developing knowledge can be used in the clinical setting. Extensive documentation is provided to enable the interested reader to obtain further information.

Sequence analysis of the spacer region between the RHD and RHCE genes

Numerous variants of the Rh blood group system, discovered by Levine and Stetson in 1939, have been detected and more than forty antigens have been identified. By performing the molecular genetic analysis of the introns as well as the exons in both RH genes, it was elucidated that Rh variants were generated by gene conversion or recombination, deletions, or mutations. For understanding the generation of many Rh variants and Rh antigens in detail, it is necessary to analyze not only the RHCE and RHD genes but also the structure and the physical distance between both these RH genes. In order to achieve the aforesaid purpose, the spacer region between the RHD and RHCE genes were amplified by the long PCR method. Therefore the full spacer region was determined to be 12159 bp in length and contained the Alu consensus sequences and the putative CpG island. It was probable that the duplication of both RH genes occurred within about 12 kb region. Analysis of the spacer region provides new information for the research on the transcription-control region, the molecular evolution of RH genes, Rh variants, and the deletion of the RHD gene in Rh blood group system.