Antibody-mediated immune suppression of erythrocyte alloimmunization can occur independently from red cell clearance or epitope masking in a murine model.

Anti-D can prevent immunization to the RhD Ag on RBCs, a phenomenon commonly termed Ab-mediated immune suppression (AMIS). The most accepted theory to explain this effect has been the rapid clearance of RBCs. In mouse models using SRBC, these xenogeneic cells are always rapidly cleared even without Ab, and involvement of epitope masking of the SRBC Ags by the AMIS-inducing Ab (anti-SRBC) has been suggested. To address these hypotheses, we immunized mice with murine transgenic RBCs expressing the HOD Ag (hen egg lysozyme [HEL], in sequence with ovalbumin, and the human Duffy transmembrane protein) in the presence of polyclonal Abs or mAbs to the HOD molecule. The isotype, specificity, and ability to induce AMIS of these Abs were compared with accelerated clearance as well as steric hindrance of the HOD Ag. Mice made IgM and IgG reactive with the HEL portion of the molecule only. All six of the mAbs could inhibit the response. The HEL-specific Abs (4B7, IgG1; GD7, IgG2b; 2F4, IgG1) did not accelerate clearance of the HOD-RBCs and displayed partial epitope masking. The Duffy-specific Abs (MIMA 29, IgG2a; CBC-512, IgG1; K6, IgG1) all caused rapid clearance of HOD RBCs without steric hindrance. To our knowledge, this is the first demonstration of AMIS to erythrocytes in an all-murine model and shows that AMIS can occur in the absence of RBC clearance or epitope masking. The AMIS effect was also independent of IgG isotype and epitope specificity of the AMIS-inducing Ab.

SIRPα/CD172a and FHOD1 are unique markers of littoral cells, a recently evolved major cell population of red pulp of human spleen.

Asplenic individuals are compromised not only in their ability to destroy infectious agents, but are at increased risk for death from autoimmune disease, certain tumors, and ischemic heart disease. Enhanced mortality is attributed to lack of phagocytes sequestered in spleen that efficiently engulf and destroy appropriate targets, although related cells are found elsewhere. To determine whether a unique population regulates RBC-pathogen clearance and filtration of altered self, we reviewed the anatomic literature and analyzed in situ by immunohistochemistry and immunofluorescence the expression patterns of a little-characterized cell that dominates the splenic red pulp of humans and closely related primates: the venous sinus-lining or littoral cell (LC). High expression of the formin homology domain protein 1 outlines the LC population. Although LCs are endothelial-like in distribution, they express several macrophage-directed proteins, the RBC Duffy Ag receptor for chemokines and T cell coreceptor CD8α/α, yet they lack lineage-associated markers CD34 and CD45. Strikingly, SIRPα (CD172a) expression in human spleen concentrates on LCs, consistent with recent demonstration of a key role in RBC turnover and elimination versus release of infected or altered self. Our results indicate human LCs (SIRPα(+), formin homology domain protein 1(+), CD8α/α(+), CD34(-), CD45(-)) comprise a highly plastic barrier cell population that emerged late in primate evolution coordinate with CD8 expression. Unique to Hominidae, LCs may be the ultimate determinant of which cells recirculate after passage through human spleen.

Activation state of alpha4beta1 integrin on sickle red blood cells is linked to the duffy antigen receptor for chemokines (DARC) expression.

In sickle cell anemia, reticulocytes express enhanced levels of α4ß1 integrin that interact mainly with vascular cell adhesion molecule-1 and fibronectin, promoting vaso-occlusion. These interactions are known to be highly sensitive to the inflammatory chemokine IL-8. The Duffy antigen receptor for chemokines (DARC) modulates the function of inflammatory processes. However, the link between α4ß1 activation by chemokines and DARC erythroid expression is not or poorly explored. Therefore, the capacity of α4ß1 to mediate Duffy-negative and Duffy-positive sickle reticulocyte (SRe) adhesion to immobilized vascular cell adhesion molecule-1 and fibronectin was evaluated. Using static adhesion assays, we found that, under basal conditions, Duffy-positive SRe adhesion was 2-fold higher than that of Duffy-negative SRes. Incubating the cells with IL-8 or RANTES (regulated on activation normal T cell expressed and secreted) increased Duffy-positive SRe adhesion only, whereas Mn(2+) increased cell adhesion independently of the Duffy phenotype. Flow cytometry analyses performed with anti-ß1 and anti-α4 antibodies, including a conformation-sensitive one, in the presence or absence of IL-8, revealed that Duffy-positive and Duffy-negative SRes displayed similar erythroid α4ß1 expression levels, but with distinct activation states. IL-8 did not affect α4ß1 affinity in Duffy-positive SRes but induced its clustering as corroborated by immunofluorescence microscopy. Our results indicate that in Duffy-negative SRes α4ß1 integrin is constitutively expressed in a low affinity state, whereas in Duffy-positive SRes α4ß1 is expressed in a higher chemokine-sensitive affinity state. This activation state associated with DARC RBC expression may influence the intensity of the inflammatory responses encountered in sickle cell anemia and participate in its interindividual clinical expression variability.

Expression of blood group genes by mesenchymal stem cells.

Incompatible blood group antigens are highly immunogenic and can cause graft rejections. Focusing on distinct carbohydrate- and protein-based membrane structures, defined by blood group antigens, we investigated human bone marrow-derived mesenchymal stem cells (MSCs) cultured in human serum. The presence of H (CD173), ABO, RhD, RhCE, RhAG, Kell, urea transporter type B (SLC14A1, previously known as JK), and Duffy antigen receptor of chemokines (DARC) was evaluated at the levels of genome, transcriptome and antigen. Fucosyltransferase-1 (FUT1), RHCE, KEL, SLC14A1 (JK) and DARC mRNA were transcribed in MSCs. FUT1 mRNA transcription was lost during differentiation. The mRNA transcription of SLC14A1 (JK) decreased during chondrogenic differentiation, while that of DARC increased during adipogenic differentiation. All MSCs synthesized SLC14A1 (JK) but no DARC protein. However, none of the protein antigens tested occurred on the surface, indicating a lack of associated protein function in the membrane. As A and B antigens are neither expressed nor adsorbed, concerns of ABO compatibility with human serum supplements during culture are alleviated. The H antigen expression by GD2dim+ MSCs identified two distinct MSC subpopulations and enabled their isolation. We hypothesize that GD2(dim+) H(+) MSCs retain a better 'stemness'. Because immunogenic blood group antigens are lacking, they cannot affect MSC engraftment in vivo, which is promising for clinical applications.

Coexpression of atypical chemokine binders (ACBs) in breast cancer predicts better outcomes.

Some evidence suggests that atypical chemokine binders (ACBs) including DARC, D6, and CCX-CKR play an important role in inhibiting invasion and metastasis of cancer cells; however, their expression in breast cancer has not been well characterized. The purpose of this study was to determine the predictive value of ACBs for relapse-free survival and overall survival in breast cancer. The expressions of the three molecules were analyzed immunohistochemically in a total of 558 consecutive breast specimens comprising 12 normal breast tissues, 29 noninvasive (carcinoma in situ), and 517 invasive breast carcinoma and their relationships to clinicopathological features and survival were investigated in invasive breast cancer. Coexpression of ACBs in invasive breast carcinoma (55.9%) was much lower that of noninvasive breast carcinoma (93.1%) and normal breast tissue (100.0%), P = 0.0004, 0.0096, respectively. Their separate stainings in invasive cancer were significantly conversely correlated with lymph node status and tumor stage. In univariate analysis, the three proteins and their coexpression were significantly associated with higher relapse-free survival and overall survival. In multivariate analysis, each of these molecules was favorable for relapse-free survival, but not overall survival. Surprisingly, their coexpression was not only independently prognostic factor for relapse-free survival (RR = 0.182, 95% CI: 0.101-0.327, P < 0.001), but also for overall survival (RR = 0.271, 95% CI: 0.081-0.910, P = 0.035). These findings highlight that the multiple loss of ACBs may occur during the development of tumorigenesis and their coexpression in breast cancer is predictive of favorable outcomes.

Co-expression network analysis identified atypical chemokine receptor 1 (ACKR1) association with lymph node metastasis and prognosis in cervical cancer.

Cervical cancer (CC) is one kind of female cancer. With the development of bioinformatics, targeted specific biomarkers therapy has become much more valuable. GSE26511 was obtained from gene expression omnibus (GEO). We utilized a package called "WGCNA" to build co-expression network and choose the hub module. Search Tool for the Retrieval of Interacting Genes Database (STRING) was used to analyze protein-protein interaction (PPI) information of those genes in the hub module. A Plug-in called MCODE was utilized to choose hub clusters of PPI network, which was visualized in Cytoscape. Clusterprofiler was used to do functional analysis. Univariate and multivariate cox proportional hazards regression analysis were both conducted to predict the risk score of CC patients. Kaplan-Meier curve analysis was done to show the overall survival. Receiver operating characteristic (ROC) curve analysis was utilized to evaluate the predictive value of the patient outcome. Validation of the hub gene in databases, Gene set enrichment analysis (GSEA) and GEPIA were completed. We built co-expression network based on GSE26511 and one CC-related module was identified. Functional analysis of this module showed that extracellular space and Signaling pathways regulating pluripotency of stem cells were most related pathways. PPI network screened GNG11 as the most valuable protein. Cox analysis showed that ACKR1 was negatively correlated with CC progression, which was validated in Gene Expression Profiling Interactive Analysis (GEPIA) and datasets. Survival analysis was performed and showed the consistent result. GSEA set enrichment analysis was also completed. This study showed hub functional terms and gene participated in CC and then speculated that ACKR1 might be tumor suppressor for CC.

K562 erythroleukemia line as a possible reticulocyte source to culture Plasmodium vivax and its surrogates.

Establishing an in vitro "red blood cell matrix" that would allow uninterrupted access to a stable, homogeneous reticulocyte population would facilitate the establishment of continuous, long-term in vitro Plasmodium vivax blood stage cultures. In this study, we have explored the suitability of the erythroleukemia K562 cell line as a continuous source of such reticulocytes and have investigated regulatory factors behind the terminal differentiation (and enucleation, in particular) of this cell line that can be used to drive the reticulocyte production process. The Duffy blood group antigen receptor (Fy), essential for P. vivax invasion, was stably introduced into K562 cells by lentiviral gene transfer. miRNA-26a-5p and miRNA-30a-5p were downregulated to promote erythroid differentiation and enucleation, resulting in a tenfold increase in the production of reticulocytes after stimulation with an induction cocktail compared with controls. Our results suggest an interplay in the mechanisms of action of miRNA-26a-5p and miRNA-30a-5p, which makes it necessary to downregulate both miRNAs to achieve a stable enucleation rate and Fy receptor expression. In the context of establishing P. vivax-permissive, stable, and reproducible reticulocytes, a higher enucleation rate may be desirable, which may be achieved by the targeting of further regulatory mechanisms in Fy-K562 cells; promoting the shift in hemoglobin production from fetal to adult may also be necessary. Despite the fact that K562 erythroleukemia cell lines are of neoplastic origin, this cell line offers a versatile model system to research the regulatory mechanisms underlying erythropoiesis.

Duffy antigen expression on reticulocytes does not alter following blood loss in an autologous donation model.

BACKGROUND: The Duffy blood group (Fy) antigen functions as the receptor whereby the malarial parasite Plasmodium vivax invades reticulocytes. In this study, we evaluated an autologous blood donation model to measure Fy expression during the anticipated response to blood loss. AIMS: This study aims to examine Fy expression following anticipated reticulocytosis in response to blood loss from autologous whole blood donation. METHOD: Subjects were healthy blood donors presenting for planned collection of two or three autologous units. Whole blood (450 ml +/- 10%) was collected and processed. Blood samples for Fy testing were obtained from the donations. These were assayed by flow cytometry by measuring binding of a phycoerythrin-labelled anti-Fy6 antibody and compared against reticulocyte numbers. Reticulocyte numbers were measured using thiazole orange. Results were compared from baseline (first donation) with samples at second and, if available, third, donations. Phenotyping for Fy a and b antigens was performed. RESULTS: Reticulocytes increased by a mean of 37% over baseline [0.93% (range 0.31-1.93) to 1.23% (0.32-3.51%)] following donation of two (n = 32) or three (n = 9) autologous whole blood units. Absolute reticulocyte count remained low. Mean and median Fy expression on mature red blood cells and reticulocytes did not change from baseline levels despite individual variation. No apparent relationship to serologically determined Fy a and/or b antigen status was present. CONCLUSION: Baseline expression of Fy antigen on mature red blood cells and reticulocytes is quite variable between individuals, but appears not to be greatly affected by mild to moderate reticulocytosis following blood loss in an autologous blood donation model.

Opposing roles of murine duffy antigen receptor for chemokine and murine CXC chemokine receptor-2 receptors in murine melanoma tumor growth.

The Duffy antigen receptor for chemokines (DARC) has been classified as a "silent" receptor, as it can bind CXC and CC chemokines to undergo ligand-induced receptor internalization, but is not coupled to trimeric G proteins required for the classic G protein-coupled receptor-mediated signaling. CXC chemokine receptor-2 (CXCR2) has been shown to play a major role in tumor angiogenesis. To test the hypothesis that these two chemokine receptors might play opposing roles in the growth of melanoma tumors, we developed a transgenic mouse model, where the preproendothelin promoter/enhancer (PPEP) is used to drive expression of either murine DARC (mDARC) or murine CXCR2 (mCXCR2) in endothelial cells. We show herein that the growth of melanoma tumor xenografts, established from s.c. injection of immortalized murine melanocytes overexpressing macrophage inflammatory protein-2, was inhibited or enhanced in the PPEP-mDARC and PPEP-mCXCR2 transgenic mice, respectively, compared with control mice. The early tumors formed in mDARC transgenic mice exhibited a significantly higher number of infiltrating leukocytes compared with either the control or mCXCR2 transgenic mice, suggesting a potential role for DARC expressed on endothelial cells in leukocyte migration. In addition, the tumor-associated angiogenesis in mDARC transgenic mice was reduced when compared with the control. Conversely, tumor angiogenesis was significantly increased in mCXCR2 transgenic mice. Results indicate that endothelial cell overexpression of mDARC increased leukocyte trafficking to the tumor, reduced the growth of blood vessels into the tumor, and reduced the growth rate of the tumor, whereas endothelial cell overexpression of mCXCR2 had the reverse effect on tumor angiogenesis and growth.

Molecular basis of the Duffy blood group system.

ACKR1, located on chromosome 1q23.2, is the gene that encodes a glycoprotein expressing the Duffy blood group antigens. This gene is transcribed in two mRNA variants yielding two isoforms, encoding proteins with 338 and 336 amino acids. This review provides a general overview of the Duffy blood group to characterise and elucidate the genetic basis of this system. The Fya and Fyb antigens are encoded by co-dominant FY*A (FY*01) and FY*B (FY*02) alleles, which differ by c.125G>A (rs12075), defining the Fy(a+b-), Fy(a-b+) and Fy(a+b+) phenotypes. The Fy(a-b-) phenotype that occurs in Africans provides an explanation for the apparent absence of Plasmodium vivax in this region: this phenotype arises from homozygosity for the FY*B allele carrying a point mutation c.1-67T>C (rs2814778), which prevents Fyb antigen expression only in red blood cells. The same mutation has also been found on the FY*A allele, but it is very rare. The Fy(a-b-) phenotype in Europeans and Asians arises from mutations in the coding region of the FY*A or FY*B allele, preventing Duffy antigen expression on any cell in the body and thus are true Duffy null phenotypes. According to the International Society for Blood Transfusion, ten alleles are associated with the null expression of the Fy antigens. Furthermore, different allelic forms of FY*B modify Fyb antigen expression, which may result in very weak or equivocal serology results. The mostly common found variants, c.265C>T (rs34599082) and c.298G>A (rs13962) -previously defined in combination only with the FY*B allele - have already been observed in the FY*A allele. Thus, six alleles have been recognised and associated with weak expression of the Fy antigens. Considering the importance of the Duffy blood group system in clinical medicine, additional studies via molecular biology approaches must be performed to resolve and clarify the discrepant results that are present in the erythrocyte phenotyping.

Enhanced expression of Duffy antigen receptor for chemokines by breast cancer cells attenuates growth and metastasis potential.

In addition to the role in regulating leukocyte trafficking, chemokines recently have been shown to be involved in cancer growth and metastasis. Chemokine network in tumor neovascularity may be regulated by decoy receptors. Duffy antigen receptor for chemokines (DARC) is a specific decoy receptor binding with the angiogenic CC and CXC chemokines. To investigate the effects of DARC on the tumorigenesis and the metastasis potential of human breast cancer cells, human DARC cDNA was reintroduced into the MDA-MB-231 and MDA-MB-435HM cells which have a high capability of spontaneous pulmonary metastasis. We demonstrated that DARC overexpression induced inhibition of tumorigenesis and/or metastasis through interfering with the tumor angiogenesis in vivo. This inhibition is associated with decreasing CCL2 protein levels, and MVD and MMP-9 expression in xenograft tumors. In human breast cancer samples, we also demonstrated that low expression of the DARC protein is significantly associated with estrogen receptor (ER) status, MVD, lymph node metastasis, distant metastasis and poor survival. Our results suggest for the first time that DARC is a negative regulator of growth in breast cancer, mainly by sequestration of angiogenic chemokines and subsequent inhibition of tumor neovascularity.

[Duffy antigen receptor for chemokines attenuates breast cancer growth and metastasis: an experiment with nude mice].

OBJECTIVE: To study the effects of Duffy antigen receptor for chemokines (DARC) on the tumorigenesis and metastasis of breast cancer. METHODS: Human breast cancer cells of the line MDA-MB-435HM with a great potentiality of metastasis were cultured and then divided into 3 groups: MDA-MB-435HM-DARC cell group, to be transfected with pcDNA3/DARC FyB containing human DARC cDNA; MDA-MB-435HM-vect cell group, to be transfected with blank plasmid pcDNA3; and MDA-MB-435HM cell group without transfection. Female BALB/c nude mice were implanted with MDA-MB-435HM cells into the nipple. The size of the implanted cancer was measured once a week. The mice were killed 4, 6, and 8 weeks after the implantation respectively and their lungs were taken out to observe the number of metastatic tumor. Immunohistochemical staining was performed to calculate the microvascular density (MVD). Western blotting was used to detect the matrix metalloproteinase (MMP)-9 protein expression of the lung tissues. ELISA was used to detect the concentrations of the 2 DARC ligands: CNCL8 and CCL2 in the supernatant of culture fluid of the 3 kinds of cells and the metastatic tumors. RESULTS: The expression levels of DARC mRNA and protein of the MDA-MB-435HM cells were 38% those of the MDA-MB-435 cells. The expression levels of CXCL8 and CCL2 of the MDA-MB-435HM-DARC cells were significantly lower than those of the MDA-MB-435HM-vect cells and MDA-MB-435HM cells (both P < 0.05). All mice developed tumor with a tumorigenesis rate of 100%. However, the tumor occurred 17 days after implantation in those mice implanted with MDA-MB-435HM-DARC cells, significantly later then in those implanted with MDA-MB-435HM-vect cells and MDA-MB-435HM cells (9 and 10 days after implantation) the size of tumor in the former group being significantly smaller than those of the 2 latter groups (both P < 0.01). The number of metastatic foci in the lung of the MDA-MB-435HM-DARC group was significantly less than those of the other 2 groups (both P < 0.01). The level of CCI2 of the implanted tumor in the MDA-MB-435HM-DARC group was significantly lower than those of the other 2 groups (both P < 0.01). The MVD of the MDA-MB-435HM-DARC was significantly less than those of the other 2 groups (both P < 0.01) and most of the vessels of the MDA-MB-435HM-DARC group were not newly formed vessels with a diameter < 8 red blood cells. The MMP-9 protein expression levels of the MDA-MB-435HM-vect cells and MDA-MB-435HM-cells were 3.1 and 3.4 times that of the MDA-MB-435HM-DARC group (both P < 0.05). CONCLUSION: DARC, a chemokine decoy receptor, inhibits the chemokine-induced angiogenesis, thus inhibiting the growth and lung metastasis of breast cancer.

Duffy antigen receptor for chemokines and CXCL5 are essential for the recruitment of neutrophils in a multicellular model of rheumatoid arthritis synovium.

OBJECTIVE: The role of chemokines and their transporters in rheumatoid arthritis (RA) is poorly described. Evidence suggests that CXCL5 plays an important role, because it is abundant in RA tissue, and its neutralization moderates joint damage in animal models of arthritis. Expression of the chemokine transporter Duffy antigen receptor for chemokines (DARC) is also up-regulated in early RA. The aim of this study was to investigate the role of CXCL5 and DARC in regulating neutrophil recruitment, using an in vitro model of RA synovium. METHODS: To model RA synovium, RA synovial fibroblasts (RASFs) were cocultured with endothelial cells (ECs) for 24 hours. Gene expression in cocultured cells was investigated using TaqMan gene arrays. The roles of CXCL5 and DARC were determined by incorporating cocultures into a flow-based adhesion assay, in which their function was demonstrated by blocking neutrophil recruitment with neutralizing reagents. RESULTS: EC-RASF coculture induced chemokine expression in both cell types. Although the expression of CXC chemokines was modestly up-regulated in ECs, the expression of CXCL1, CXCL5, and CXCL8 was greatly increased in RASFs. RASFs also promoted the recruitment of flowing neutrophils to ECs. Anti-CXCL5 antibody abolished neutrophil recruitment by neutralizing CXCL5 expressed on ECs or when used to immunodeplete coculture-conditioned medium. DARC was also induced on ECs by coculture, and anti-Fy6 antibody or small interfering RNA targeting of DARC expression effectively abolished neutrophil recruitment. CONCLUSION: This study is the first to demonstrate, in a model of human disease, that the function of DARC is essential for editing the chemokine signals presented by ECs and for promoting unwanted leukocyte recruitment.

HIV and chemokine binding to red blood cells--DARC matters.

A mutation in the Duffy antigen (DARC) that abrogates receptor expression and gives profound protection against some malaria species has become almost universal in African populations. He et al. (2008) show that this polymorphism also leads to significantly increased susceptibility to HIV-1 infection but, paradoxically, to prolonged survival in HIV-1-infected subjects.

Duffy antigen receptor for chemokines mediates trans-infection of HIV-1 from red blood cells to target cells and affects HIV-AIDS susceptibility.

Duffy antigen receptor for chemokines (DARC) expressed on red blood cells (RBCs) influences plasma levels of HIV-1-suppressive and proinflammatory chemokines such as CCL5/RANTES. DARC is also the RBC receptor for Plasmodium vivax. Africans with DARC -46C/C genotype, which confers a DARC-negative phenotype, are resistant to vivax malaria. Here, we show that HIV-1 attaches to RBCs via DARC, effecting trans-infection of target cells. In African Americans, DARC -46C/C is associated with 40% increase in the odds of acquiring HIV-1. If extrapolated to Africans, approximately 11% of the HIV-1 burden in Africa may be linked to this genotype. After infection occurs, however, DARC-negative RBC status is associated with slower disease progression. Furthermore, the disease-accelerating effect of a previously described CCL5 polymorphism is evident only in DARC-expressing and not in DARC-negative HIV-infected individuals. Thus, DARC influences HIV/AIDS susceptibility by mediating trans-infection of HIV-1 and by affecting both chemokine-HIV interactions and chemokine-driven inflammation.

Arg89Cys substitution results in very low membrane expression of the Duffy antigen/receptor for chemokines in Fy(x) individuals.

The Duffy (FY) blood group antigens are carried by the DARC glycoprotein, a widely expressed chemokine receptor. The molecular basis of the Fya/Fyb and Fy(a-b-) polymorphisms has been clarified, but little is known about the Fyx antigen and the FY*X allele associated with weak expression of Fyb, Fy3, Fy5, and Fy6 antigens. We analyzed here the structure and expression of the FY gene in 4 Fy(a-bweak) individuals. As compared with Fy(a-b+) controls, the Fy(a-bweak) red blood cell membranes contained residual amount of DARC polypeptide and these cells were poorly bound by anti-Fy antibodies and chemokines. The FY gene from Fy(a-b+) and Fy(a-bweak) individuals differed by one substitution, C286T. The resulting Arg89Cys amino acid change reduced the binding of anti-Fy antibodies and chemokines to DARC transfectants. We concluded that the Fybweak donors carried the FY*X allele at the FY locus and that the Fyx antigen corresponds to highly reduced expression of a grossly normal Fyb polypeptide caused by the Arg89Cys substitution. Because FY is a single copy gene, this defect should also affect DARC expression in nonerythroid cells. Because the Fyx phenotype is not associated with apparent clinical consequences, we discussed these findings in the light of the putative roles of DARC in various tissues. Finally, we developed a Fyx DNA typing assay that should be useful for genetic studies and clinical transfusion medicine.

Induction of Duffy gene (FY) in human endothelial cells and in mouse.

Duffy Blood Group protein is a glycoprotein with seven transmembrane domains that binds to C-X-C and C-C chemokines. The antigen is constitutively expressed in endothelial and epithelial cells of several nonerythroid tissues and in Purkinje cells of the cerebellum. We studied the effect of proinflammatory cytokines on Duffy gene expression in endothelial cells from human umbilical vein (HUVEC) and human pulmonary arteries (HPAEC). Also, we studied the effect of inflammatory agents like bacterial lipopolysaccharide (LPS) on Duffy gene induction in mouse. Reverse transcription-PCR and mRNA blot analyses showed that Duffy mRNA was present in these cells in negligible amounts. However, treatment with tumor necrosis factor-alpha for 6-24h resulted in a 5 to 8-fold increase in Duffy mRNA. On the other hand, treatment with interleukin-1 (IL-1), IL-6 or LPS did not have any effect. Fluorescence microscopy and fluorescence activated cell sorting showed greater expression of Duffy protein in treated cells correlating the increase in mRNA synthesis with an increase in antigen production. In mice, Duffy gene was induced in lungs and brain with LPS treatment indicating that the induction is a physiological event. Vascular endothelial cells may induce Duffy protein to regulate leukocytes and/or chemokine trafficking.

Expression of the Duffy antigen in K562 cells. Evidence that it is the human erythrocyte chemokine receptor.

The human malarial parasite Plasmodium vivax invades erythrocytes by binding to a cell surface protein identified as the Duffy blood group antigen. The molecular properties of the Duffy antigen, which was recently cloned, are very similar to those of a chemokine binding protein known as the human erythrocyte chemokine receptor. This has led to the suggestion that these two molecules are the same protein. To further investigate the suspected double identity of the Duffy antigen we have transfected it into a human erythroleukemic cell line, K562. Cells stably expressing the Duffy antigen were isolated and used to characterize the protein. K562 cells transfected with the Duffy antigen displayed specific 125I-melanoma growth-stimulating activity (MGSA) binding while mock transfected cells did not. Comparison of 125I-MGSA binding to the Duffy antigen and the human erythrocyte chemokine receptor showed that the specific 125I-MGSA binding to both proteins was displaced by excess unlabeled MGSA, interleukin-8, RANTES, monocyte chemotactic peptide-1, and platelet factor 4, but not by macrophage inflammatory protein-1 alpha or -1 beta. Scatchard analysis of competition binding studies with these unlabeled chemokines revealed high affinity binding to the Duffy antigen with KD binding values of 24 +/- 4.9, 20 +/- 4.7, 41.9 +/- 12.8, and 33.9 +/- 7 nM for MGSA, interleukin-8, RANTES, and monocyte chemotactic peptide-1, respectively. A monoclonal antibody, Fy6, to the Duffy antigen inhibited 125I-MGSA binding to K562 cells expressing the Duffy antigen. Cell membranes from K562 cells permanently expressing the Duffy antigen were chemically cross-linked with 125I-MGSA. SDS-polyacrylamide gel electrophoresis analysis of the cross-linked products showed covalent incorporation of radiolabeled MGSA into a protein of molecular mass 47 kDa, and cross-linking was inhibited in the presence of unlabeled MGSA. These studies provide evidence that the Duffy blood group antigen is the same protein as the human erythrocyte chemokine receptor.

Duffy antigen facilitates movement of chemokine across the endothelium in vitro and promotes neutrophil transmigration in vitro and in vivo.

The Duffy Ag expressed on RBCs, capillaries, and postcapillary venular endothelial cells binds selective CXC and CC chemokines with high affinity. Cells transfected with the Duffy Ag internalize but do not degrade chemokine ligand. It has been proposed that Duffy Ag transports chemokines across the endothelium. We hypothesized that Duffy Ag participates in the movement of chemokines across the endothelium and, by doing so, modifies neutrophil transmigration. We found that the Duffy Ag transfected into human endothelial cells facilitates movement of the radiolabeled CXC chemokine, growth related oncogene-alpha/CXC chemokine ligand 1 (GRO-alpha/CXCL1), across an endothelial monolayer. In addition, neutrophil migration toward GRO-alpha/CXCL1 and IL-8 (IL-8/CXCL8) was enhanced across an endothelial monolayer expressing the Duffy Ag. Furthermore, GRO-alpha/CXCL1 stimulation of endothelial cells expressing the Duffy Ag did not affect gene expression by oligonucleotide microarray analysis. These in vitro observations are supported by the finding that IL-8/CXCL8-driven neutrophil recruitment into the lungs was markedly attenuated in transgenic mice lacking the Duffy Ag. We conclude that Duffy Ag has a role in enhancing leukocyte recruitment to sites of inflammation by facilitating movement of chemokines across the endothelium.