Confirmation of Duffy blood group antigen locus (FY) at 1q22-->q23 by fluorescence in situ hybridization

Allelic frequency variation of ACKR1 in three Algerian populations: Zenata, Reguibat, and Oran

INTRODUCTION

The discovery of the Duffy antigen is of great significance, given its essential role in immune response and various physiological processes. Genetic mutations in the Duffy gene not only affect antigen expression but also result in different antigen types. This underscores the importance of genetic characterization for clinical studies and exploring genetic diversity within the population. This study primarily aims to genetically characterize the Duffy blood group within three Algerian populations: the Zenata, Reguibat, and Oran populations.

METHODS

The genetic polymorphism of the Duffy erythrocyte group was examined, focusing on five allelic versions of the ACKR1 locus: FY*01, FY*02, FY*X, and silent alleles FY*01 N.01 and FY*02 N.01. A total of 223 Algerian individuals, including 90 from the Oran population, 66 from the Zenata population, and 67 from the Reguibat population, were analyzed using the polymerase chain reaction with sequence-specific primer (PCR-SSP) method. The results revealed the presence of the silent alleles (FY*01 N.01 and FY*02 N.01) in all three populations, with a total frequency of 78.03% in the Zenata population. Additionally, the FY*X allele was exclusively detected in the Reguibat population, with a frequency of 0.75% CONCLUSION: This study provides valuable insights into the allele and genotypic frequencies of the Duffy system in the Zenata, Reguibat and Oranpopulations, contributing to our understanding of the genetic history and origins of the Algerian population. Further research incorporating additional genetic markers and establishing a comprehensive database would enhance our knowledge in this area.

Distribution of the Duffy genotypes in Malaysian Borneo and its relation to Plasmodium knowlesi malaria susceptibility

The Duffy blood group plays a key role in Plasmodium knowlesi and Plasmodium vivax invasion into human erythrocytes. The geographical distribution of the Duffy alleles differs between regions with the FY*A allele having high frequencies in many Asian populations, the FY*B allele is found predominately in European populations and the FY*B^es allele found predominantly in African regions. A previous study in Peninsular Malaysia indicated high homogeneity of the dominant FY*A/FY*A genotype. However, the distribution of the Duffy genotypes in Malaysian Borneo is currently unknown. In the present study, the distribution of Duffy blood group genotypes and allelic frequencies among P. knowlesi infected patients as well as healthy individuals in Malaysian Borneo were determined. A total of 79 P. knowlesi patient blood samples and 76 healthy donor samples were genotyped using allele specific polymerase chain reaction (ASP-PCR). Subsequently a P. knowlesi invasion assay was carried out on FY*AB/ FY*A and FY*A/ FY*A Duffy genotype blood to investigate if either genotype conferred increased susceptibility to P. knowlesi invasion. Our results show almost equal distribution between the homozygous FY*A/FY*A and heterozygous FY*A/FY*B genotypes. This is in stark contrast to the Duffy distribution in Peninsular Malaysia and the surrounding Southeast Asian region which is dominantly FY*A/FY*A. The mean percent invasion of FY*A/FY*A and FY*A/FY*B blood was not significantly different indicating that neither blood group confers increased susceptibility to P. knowlesi invasion.

Duffy blood group system: New genotyping method and distribution in a Brazilian extra-Amazonian population

Duffy blood group system is of interest in several fields of science including transfusion medicine, immunology and malariology. Although some methods have been developed for Duffy polymorphism genotyping, not all of them have been sufficiently described and validated, and all present limitations. At the same time, the frequency of Duffy alleles and antigens in some densely populated regions of the world are still missing. In this study we present new tests for genotyping the major alleles of the Duffy blood system and describe Duffy alleles and antigens in blood donors and transfusion-dependent patients in Minas Gerais, Brazil. A simple and reproducible strategy was devised for Duffy genotyping based on real-time PCR that included SNPs rs12075 and rs2814778. No significant differences between the allele frequencies were observed comparing blood donors and patients. Among the blood donors, the phenotype Fy(a-b+) was the most common and the Fy(a-b-) phenotype, associated with populations of African descent, was remarkably less common among subjects who self-identified as black in comparison to other ethnoracial categories. However, the African ancestry estimated by molecular markers was significantly higher in individuals with the allele associated to the Duffy null phenotype. The genotyping method presented may be useful to study Duffy genotypes accurately in different contexts and populations. The results suggest a reduced risk of alloimmunization for Duffy antigens and increased susceptibility for malaria in Minas Gerais, considering the high frequency of Duffy-positive individuals.

Genotyping of the Duffy blood group among Plasmodium knowlesi-infected patients in Malaysia

The Duffy blood group is of major interest in clinical medicine as it plays an important role in Plasmodium knowlesi and Plasmodium vivax infection. In the present study, the distribution of Duffy blood group genotypes and allelic frequencies among P. knowlesi infected patients as well as healthy individuals in Peninsular Malaysia were determined. The blood group of 60 healthy blood donors and 51 P. knowlesi malaria patients were genotyped using allele specific polymerase chain reaction (ASP-PCR). The data was analyzed using Fisher's exact test in order to assess the significance of the variables. Our results show a high proportion of the FY*A/FY*A genotype (>85% for both groups) and a high frequency of the FY*A allele (>90% for both groups). The FY*A/FY*A genotype was the most predominant genotype in both infected and healthy blood samples. The genotype frequency did not differ significantly between the donor blood and the malaria patient groups. Also, there was no significant correlation between susceptibility to P. knowlesi infection with any Duffy blood genotype.

Duffy blood group and malaria

Very important progress has been made over the last years in understanding the Duffy blood group system and its complexity. The Duffy blood group antigen serves not only as blood group antigen, but also as a receptor for a family of proinflammatory cytokines termed chemokines, and as a receptor for Plasmodium vivax malaria parasites. The Duffy antigen has been termed the "Duffy Antigen Receptor for Chemokines" (DARC) or the Duffy chemokine receptor. DARC might play a role as a scanvenger on the red blood cell surface to eliminate excess of toxic chemokines produced in some pathologic situations [48]. Plasmodium vivax (P. vivax) causes approximately between 70 and 80 million cases of malaria per year and is the most amply distributed human malaria in the world [51]. Individuals with the Duffy-negative phenotype are resistant to P. vivax invasion, and the molecular mechanism that gives rise to the phenotype Fy(a - b - ) in black individuals has been associated with a point mutation - 33TC expressed in homozigosity in the FYB allele [5]. Despite P. vivax be widespread throughout the tropical and subtropical world, it is absent from West Africa, where more than 95% of the population is Duffy negative. Recently, this point mutation has been described in heterozigosity in the FYA allele in others malaria endemic regions [7, 8], and until now we do not know if it confers a certain degree of protection against P. vivax infection.

Red blood cell polymorphism and susceptibility to Plasmodium vivax

Resistance to Plasmodium vivax blood-stage infection has been widely recognised to result from absence of the Duffy (Fy) blood group from the surface of red blood cells (RBCs) in individuals of African descent. Interestingly, recent studies from different malaria-endemic regions have begun to reveal new perspectives on the association between Duffy gene polymorphism and P. vivax malaria. In Papua New Guinea and the Americas, heterozygous carriers of a Duffy-negative allele are less susceptible to P. vivax infection than Duffy-positive homozygotes. In Brazil, studies show that the Fy(a) antigen, compared to Fy(b), is associated with lower binding to the P. vivax Duffy-binding protein and reduced susceptibility to vivax malaria. Additionally, it is interesting that numerous studies have now shown that P. vivax can infect RBCs and cause clinical disease in Duffy-negative people. This suggests that the relationship between P. vivax and the Duffy antigen is more complex than customarily described. Evidence of P. vivax Duffy-independent red cell invasion indicates that the parasite must be evolving alternative red cell invasion pathways. In this chapter, we review the evidence for P. vivax Duffy-dependent and Duffy-independent red cell invasion. We also consider the influence of further host gene polymorphism associated with malaria endemicity on susceptibility to vivax malaria. The interaction between the parasite and the RBC has significant potential to influence the effectiveness of P. vivax-specific vaccines and drug treatments. Ultimately, the relationships between red cell polymorphisms and P. vivax blood-stage infection will influence our estimates on the population at risk and efforts to eliminate vivax malaria.

Acquired antibody responses against Plasmodium vivax infection vary with host genotype for duffy antigen receptor for chemokines (DARC)

Background

Polymorphism of the Duffy Antigen Receptor for Chemokines (DARC) is associated with susceptibility to and the severity of Plasmodium vivax malaria in humans. P. vivax uses DARC to invade erythrocytes. Individuals lacking DARC are ‘resistant’ to P. vivax erythrocytic infection. However, susceptibility to P. vivax in DARC+ individuals is reported to vary between specific DARC genotypes. We hypothesized that the natural acquisition of antibodies to P. vivax blood stages may vary with the host genotype and the level of DARC expression. Furthermore, high parasitemia has been reported to effect the acquisition of immunity against pre-erythrocytic parasites. We investigated the correlation between host DARC genotypes and the frequency and magnitude of antibodies against P. vivax erythrocytic stage antigens.

Methodology/Findings

We assessed the frequencies and magnitudes of antibody responses against P. vivax and P. falciparum sporozoite and erythrocytic antigens in Colombian donors from malaria-endemic regions. The frequency and level of naturally-acquired antibodies against the P. vivax erythrocytic antigens merozoite surface protein 1 (PvMSP1) and Duffy binding protein (PvDBP) varied with the host DARC genotypes. Donors with one negative allele (FY*B/FY*Bnull and FY*A/FY*Bnull) were more likely to have anti-PvMSP1 and anti-PvDBP antibodies than those with two positive alleles (FY*B/FY*B and FY*A/FY*B). The lower IgG3 and IgG1 components of the total IgG response may account for the decreased responses to P. vivax erythrocytic antigens with FY*A/FY*B and FY*B/FY*B genotypes. No such association was detected with P. falciparum erythrocytic antigens, which does not use DARC for erythrocyte invasion.

Conclusion/Significance

Individuals with higher DARC expression, which is associated with higher susceptibility to P. vivax infection, exhibited low frequencies and magnitudes of P. vivax blood-stage specific antibody responses. This may indicate that one of the primary mechanisms by which P. vivax evades host immunity is through DARC indirectly down-regulating humoral responses against erythrocytic invasion and development.

Duffy blood group system genotyping in an urban Tunisian population

BACKGROUND

The Duffy blood group system, besides its relevance in transfusion medicine, is of major interest for population genetics. In fact, the Duffy molecule is the only red cell receptor for Plasmodium vivax, thus the fixation of FY*silent allele in western south-Saharan Africa resulted in the absence of this type of malaria in that area (for a review see Kwiatowski, Am J Hum Genet 77:171-192, 2005). For the Duffy functional role see, for example, Daniels (Vox Sanguinis 93:331-340, 2007).

METHODS

Duffy blood group distribution in 115 unrelated Tunisians was determined using the polymerase chain reaction with sequence specific primer (PCR-SSP) method detecting the five allelic versions of the FY gene. The red cell antigenic FY phenotype, for each donor, was deduced through DNA analysis. The blood samples of the positive FY*X alleles were investigated by serological methods, mainly the fixation-elution technique.

RESULTS

The following allele frequencies were found (after having excluded FY*X, which had frequency of 0.0174): FY*1 = 0.291 (expressed 0.260; silent 0.031); FY*2 = 0.709 (expressed 0.427; silent 0.282). The most surprising result in this work is the detection of the FY*1 silent allele, usually quite rare, in four samples (1.74%). For FY*2 silent, the predominant allele in Africans, genotyping results showed a prevalence of 29.57%. The FY locus was in Hardy-Weinberg equilibrium in the present sample.

CONCLUSION

When compared with European and African data, Tunisian samples demonstrated the presence of the common signs of these two ancestries (FY*2 and FY*X for the first population; and FY*2 silent for the last one). These data confirm the mixed roots of this urban Tunisian population already suggested by numerous studies on other haematological markers.

Real-time multiplex allele-specific polymerase chain reaction for genotyping of the Duffy antigen, the Plasmodium vivax invasion receptor

BACKGROUND AND OBJECTIVES

Duffy blood group is of major interest in clinical medicine as it is not only involved in blood-transfusion risks and occasionally in neonatal haemolytic disease, but it is also the receptor for the human malaria parasite Plasmodium vivax in the erythrocyte invasion. The aim of this study was to develop a rapid and inexpensive approach for high-throughput Duffy genotyping.

MATERIALS AND METHODS

This paper reported the development of a Duffy genotyping assay based on multiplex real-time polymerase chain reaction (PCR) using SYBR Green I fluorescent dye.

RESULTS

By using this approach for Duffy genotyping we obtained the same results as that for the conventional allele-specific PCR, however, in a high-throughput assay. The Duffy genotyping of field samples demonstrated that P. vivax-infected individuals showed a significantly higher prevalence of two functional alleles than Plasmodium falciparum-infected and non-infected individuals. This finding corroborates the hypothesis that the presence of two functional alleles increases the risk of P. vivax infection.

CONCLUSION

This methodology may be suitable for epidemiological studies, particularly for exploring the relationship between Duffy alleles and malaria susceptibility, and also for identification of transfusional incompatibility in blood banks.

Functional analysis of the promoter and chromosomal localization for human LEP503, a novel lens epithelium gene

LEP503 is a novel gene product isolated from lens epithelial cells by a subtractive cDNA cloning strategy. It is highly conserved in different vertebrate species and developmentally regulated in postnatal rat lens, suggesting that LEP503 may be an important lens epithelium gene involved in the processes of lens epithelial cell differentiation. The expression of LEP503 is highly restricted to lens epithelial cells in vivo. To investigate the molecular mechanisms regulating the promoter of the human LEP503, we cloned and characterized the promoter of the human LEP503 gene. The transcription start site was localized to a nucleotide C 22 base pairs (bp) 5' of the initiation methionine codon. By reporter gene transfection experiments, we found that approximately 2.5-kb of LEP503 5'-flanking sequence directed high level luciferase activity in human lens epithelial cells; further deletion analysis revealed positive regulatory element between bp -401 and +22. Mutation analysis in each of the seven potential binding sites for transcription factors within the region between -401 and +22 showed that the AP-1 element at -131 and the Sp1 element at -48 are the most important sites for the tissue-specific expression of LEP503. Consistent with lens epithelial cell-restricted expression of LEP503 mRNA, we found that the approximately 2.5-kb 5'-flanking sequence directed high-level promoter activity in lens epithelial cells but not in other cell types. Understanding the LEP503 promoter will allow us to investigate lens epithelial cell-specific gene regulation and to uncover methods for targeting gene delivery specifically to lens epithelial cells. The LEP503 gene is mapped to human chromosome 1q22, the same location to which zonular pulverulent cataract was previously mapped.

The genetics of childhood cataract

Human congenital cataract has a diverse aetiology. In the proportion of cases where the cause is genetic, the disease shows wide phenotypic and genetic heterogeneity. Over the past few years, much research has been devoted to mapping the genes that underlie the disorder. This has been helped by the extensive array of naturally occurring and genetically engineered mouse cataract models and the abundance of human candidate genes. Most progress to date has been in the identification of genetic mutations causing autosomal dominant congenital cataract where eight genes have been implicated in cataractogenesis. Overall there is good correlation between the genetic mutations so far identified and the resulting lens phenotype but it is clear that mutations at more that one locus may give rise to similar forms of cataract. The identification of genes causing inherited forms of cataract will improve our understanding of the mechanisms underlying cataractogenesis in childhood and provide further insights into normal lens development and physiology. Perhaps more importantly, it is likely that some of the genes causing early onset cataract will be implicated in age related cataract which remains the commonest cause of blindness in the world.

The Duffy protein: a malarial and chemokine receptor

A major advance towards understanding the Duffy blood group system has been achieved with the cloning of FY, a single-copy gene located in the 1q22->q23 region of chromosome 1. The product of FY Is an acidic glycoprotein (gp-Fy), which spans the plasma membrane seven times and has an exocellular N-terminal domain and an endocellular C-terminal domain. The system consists of four alleles, five phenotypes, and five antigens. FYA, FYB, FYB(ES), and FYB(WK) are the alleles; Fy(a+b-), Fy(a-b+), Fy(a+b+), Fy(a-b+(wK)), and Fy(a-b-), are the phenotypes, and Fy(a), Fy(b), Fy3, Fy5, and Fy6 are the antigens. Fy(a-b-), or Duffy-negative individuals, lack the Duffy protein on erythrocytes and are predominantly African and American blacks. They have the FYB(Es) allele with a mutation in the promoter region, which abolishes the expression of the protein in erythrocytes only. In the few cases of non-black Fy(a-b-) individuals, a nonsense mutation prevents the synthesis of gp-Fy. In Fy(a-b+(wk)) erythrocytes, the Fy(b) antigen is weakly expressed due to a reduced amount of the protein. The Fy5 antigen includes the Rh protein, and the Fy6 antigen is defined by a murine monoclonal antibody. Gp-Fy is produced in several cell types, including endothellal cells of capillary and postcapillary venules, epithelial cells of kidney collecting ducts, and lung alveoli, as well as PurkinJe cells of the cerebellum. The Duffy protein plays a role in inflammation and in malaria Infection. The protein is a member of the superfamily of chemokine receptors and is the receptor to which certain malarial parasites bind to invade red blood cells. The parasite-specific binding site, the binding site of chemokines, and the major antigenic domains are located in overlapping regions at the exocellular N terminus of the Duffy protein.

A Novel Mutation in the Coding Sequence of the FY*B Allele of the Duffy Chemokine Receptor Gene Is Associated With an Altered Erythrocyte Phenotype

The Duffy blood group system is of clinical and biological significance. Antibodies to Duffy antigens are responsible for some cases of transfusion incompatibility and newborn hemolytic disease. The Duffy protein is a receptor for the Plasmodium vivaxerythrocyte-binding protein and is also a receptor for various chemokines (thus renamed Duffy Antigen Receptor for Chemokines [DARC]). The two Duffy polymorphic antigens, Fya and Fyb (coded by the FY*A and FY*B alleles), are present on erythrocyte membranes. The Fy(a−b−) phenotype is the predominant one in populations of black people and also occurs in other populations, including some non-Ashkenazi Jewish groups. The Fy(a−b−) phenotype has been associated with a mutation in the FY*B promoter at the GATA box that abolishes the expression of erythrocyte Duffy protein. We describe here a novel mutation, present in the FY*B coding sequence (271C → T), that is associated with some Fy(b−) phenotypes among non-Ashkenazi Jews and among Brazilian blacks. The mutation is present in Fy(b−) individuals, who have wild-type FY*B GATA and carry the previously described 304G → A substitution. The 271C → T and 304G → A can be identified by restriction enzyme–generated restriction fragment length polymorphisms. The 271C → T substitution represents a considerable change in chemical nature (Arg91 → Cys), one which may affect the antigenic determinants of DARC, and thus be of clinical significance. The mutation may have implications for some physiological roles of DARC and be of interest in malaria research and in studies of population genetics.

A Novel Mutation in the Coding Sequence of the FY*B Allele of the Duffy Chemokine Receptor Gene Is Associated With an Altered Erythrocyte Phenotype

The Duffy blood group system is of clinical and biological significance. Antibodies to Duffy antigens are responsible for some cases of transfusion incompatibility and newborn hemolytic disease. The Duffy protein is a receptor for the Plasmodium vivaxerythrocyte-binding protein and is also a receptor for various chemokines (thus renamed Duffy Antigen Receptor for Chemokines [DARC]). The two Duffy polymorphic antigens, Fya and Fyb (coded by the FY*A and FY*B alleles), are present on erythrocyte membranes. The Fy(a−b−) phenotype is the predominant one in populations of black people and also occurs in other populations, including some non-Ashkenazi Jewish groups. The Fy(a−b−) phenotype has been associated with a mutation in the FY*B promoter at the GATA box that abolishes the expression of erythrocyte Duffy protein. We describe here a novel mutation, present in the FY*B coding sequence (271C → T), that is associated with some Fy(b−) phenotypes among non-Ashkenazi Jews and among Brazilian blacks. The mutation is present in Fy(b−) individuals, who have wild-type FY*B GATA and carry the previously described 304G → A substitution. The 271C → T and 304G → A can be identified by restriction enzyme–generated restriction fragment length polymorphisms. The 271C → T substitution represents a considerable change in chemical nature (Arg91 → Cys), one which may affect the antigenic determinants of DARC, and thus be of clinical significance. The mutation may have implications for some physiological roles of DARC and be of interest in malaria research and in studies of population genetics.

A missense mutation in the human connexin50 gene (GJA8) underlies autosomal dominant "zonular pulverulent" cataract, on chromosome 1q

CZP1, a locus for autosomal dominant "zonular pulverulent" cataract, previously had been linked with the Duffy blood-group-antigen locus on chromosome 1q. Here we report genetic refinement of the CZP1 locus and show that the underlying mutation is present in GJA8, the gene for connexin50. To map the CZP1 locus we performed linkage analysis using microsatellite markers on two distantly related branches of the original Ev. pedigree, which now spans eight generations. Significantly positive two-point LOD score (Z) values were obtained for markers D1S2669 (maximum Z [Zmax] = 4.52; maximum recombination frequency [thetamax] = 0) and D1S514 (Zmax = 4.48; thetamax = 0). Multipoint analysis gave Zmax = 5.22 (thetamax = 0) at marker D1S2669. Haplotyping indicated that CZP1 probably lies in the genetic interval D1S2746-(20.6 cM)-D1S2771. Sequence analysis of the entire protein-coding region of the GJA8 gene from the pedigree detected a C-->T transition in codon 88, which introduced a novel MnlI restriction-enzyme site that also cosegregated with the cataract. This missense mutation is predicted to result in the nonconservative substitution of serine for a phylogenetically conserved proline (P88S). These studies provide the first direct evidence that GJA8 plays a vital role in the maintenance of human lens transparency and identify the genetic defect believed to underlie the first inherited disease to be linked to a human autosome.

Cloning, characterization, and mapping of a murine promiscuous chemokine receptor gene: homolog of the human Duffy gene

We report here the isolation and genomic organization of the orthologous mouse Duffy gene, named Dfy. It is a single copy gene located in chromosome 1 in a region homologous to the human Duffy gene (FY). Sequence analyses indicate that Dfy consists of two exons: exon 1 of 55 nucleotides, which encodes 7 amino acid residues; and exon 2 of 1038 nucleotides, which encodes 327 residues. The single intron consists of 462 nucleotides. The 5'-end promoter region contains motifs involved in vertebrate development in addition to potential binding sites of factors for globin transcription. The open reading frame (ORF) shows 60% homology with the human Duffy protein. However, mouse erythrocytes are serologically Duffy-negative and mouse erythrocyte membrane proteins do not cross-react with two Duffy-specific rabbit polyclonal antibodies. The deduced protein predicts a M(r) of 36,692 and carries three potential N-glycosylation sites to asparagine residues. Hydropathy analysis predicts an exocellular amino-terminal domain of 57 residues, seven transmembrane alpha-helices, and an endocellular carboxy-terminal domain of 29 residues. In bone marrow and spleen, Dfy expresses a major 1.4-kb and a minor 1.8-kb mRNA. Contrary to humans, Dfy is expressed in liver, synthesizing a 1.4-kb mRNA, and is repressed in kidney. Dfy is highly expressed in mouse brain and produces a major 8.5-kb and a minor 10.2-kb mRNA. The human erythroleukemia K562 cells, transfected with cDNA encoding the mouse Duffy-like protein and mouse erythrocytes, have the same chemokine binding profiles indicating that they contain the same protein.

Detection of Duffy Antigen in the Plasma Membranes and Caveolae of Vascular Endothelial and Epithelial Cells of Nonerythroid Organs

The nonerythroid expression of the Duffy blood group protein (gp-Fy) was confined to certain cell types. Immunocytochemistry studies of the kidney showed gp-Fy in the endothelium of glomeruli, peritubular capillaries, vasa recta, and the principal cells (epithelial) of collecting ducts. Gp-Fy was also produced in the endothelial cells of large venules and epithelial cells (type-I) of pulmonary alveoli. In the thyroid, only the endothelial cells of capillaries produced gp-Fy. In the spleen, the endothelial cells of capillaries, high endothelial venule, and sinusoids produced abundant gp-Fy. Ultrastructural studies showed that apical and basolateral plasma membrane domains, including caveolae, had gp-Fy. Immunoblot analysis showed substantially less gp-Fy in nonerythroid cells than in erythrocytes. Moreover, the analyzed nonerythroid organs of Duffy-negative individuals did not produce more gp-Fy to compensate for the lack of this protein in their erythrocytes. The nucleotide sequence and the size of kidney mRNA from a Duffy-positive individual were the same as that of bone marrow. It is assumed, therefore, that nonerythroid Duffy protein is the product of the same gene as that of bone marrow. This notion is reinforced by the fact that nonerythroid and erythroid gp-Fy have the same antigenic domains.

Duffy and receptors for P. vivax and chemotactic peptides

The Duffy blood group system consists of two principal antigens, Fya and Fyb produced by FY*A and FY*B co-dominant alleles. Antisera, anti-Fya and anti-Fyb, define four phenotypes: Fy(a+b-), Fy(a-b+), Fy(a+b+) and Fy(a-b-). Neither antiserum agglutinates Fy(a-b-) cells, the predominant phenotype in Blacks. Outside the Black population, Fy(a-b-) phenotype is very rare. Duffy antigens appear to be multimeric erythrocyte-membrane proteins composed of different subunits. A glycoprotein of 35-45 kDa, gp-Fy, is the major subunit of the complex and has antigenic determinants defined by Duffy antibodies. The protein consists of 337 amino acid residues with a M(r) of 35,733, the same as deglycosylated gp-Fy. The hydropathy map predicts an exocellular N-terminal domain of 64 residues, nine transmembrane alpha-helices, three short protruding hydrophilic loops and an endocellular C-terminal domain of 23 residues. Duffy specific transcript, a approximately 1.3 kb mRNA, is produced by the bone marrow of Duffy-positive individuals, but it is not produced by the bone marrow of Duffy-negative individuals. The same size mRNA is produced in many tissues of Duffy-positive individuals. The same tissues of Duffy-negative individuals also synthesize the same size mRNA and the same gp-Fy as that of Duffy-positive individuals. There is not, therefore, Duffy null phenotype in the Black population. The difference between FY*A and FY*B alleles is a single nucleotide change at position 306; guanine is in FY*A, and adenine is in FY*B.(ABSTRACT TRUNCATED AT 250 WORDS)