Chemokine Receptor Gene Research Articles

Deletion of the Chemokine Receptor CCR1 Prolongs Corneal Allograft Survival

Many corneal grafts undergo immune rejection, and current therapies are associated with many side effects. The purpose of this study was to identify critical chemokine pathways involved in generating the alloimmune response to corneal transplants. Orthotopic corneal transplantation was performed in fully mismatched strains. Cytokine and chemokine receptor gene expression was determined by the RNase protection assay. Knockout (KO) strains for chemokine-chemokine receptors that are upregulated after transplantation underwent corneal transplantation. Results derived from KO murine hosts were compared with cyclosporine (Cy) therapy. In addition to graft survival, graft infiltration, allospecific delayed-type hypersensitivity (DTH), and cytokine expression were compared among the recipient groups. Initial experiments revealed gene upregulation of the chemokine receptors CCR1, -2, and -5 after corneal allorejection. Although CCR1 KO hosts showed a significant increase in graft survival compared with wild-type (WT) hosts, allografts in CCR5, CCR2/CCL3(MIP-1alpha), CXCR3, CXCL10/IP-10, and CCL3/MIP-1alpha KO mice did not show a significant improvement in graft survival. Further, CCR1 KO hosts showed a significantly higher survival rate than with systemic Cy therapy in WT hosts. Moreover, graft infiltration by leukocytes and gene expression of proinflammatory cytokines were reduced in CCR1 KO mice compared with both Cy treated and untreated WT mice, as was the induction of allospecific DTH. These studies provide, for the first time, evidence that targeting of specific chemokine pathways can significantly promote survival of corneal transplants, and suggest that select deletion or suppression of CCR1 can be a useful therapeutic target in corneal transplant immunity.

Optimization of Cancer Immunotherapy by Controlling Immune Cell Trafficking and Biodistribution

An immunosurveillance system for tumor-associated antigens (TAAs) plays an important role in the elimination of cancer cells during the initial stage. Although cancer immunotherapy targeting TAAs has progressed steadily with the development of various vaccine strategies, excellent therapeutic efficacy, as evidenced by marked tumor regression and complete response, has not been reported in a clinical setting to date. To improve the therapeutic effects of cancer immunotherapy, we are attempting to establish an innovative concept, the "cell delivery system," capable of better controlling the trafficking and biodistribution of immune cells by applying chemokine-chemokine receptor coupling, which regulates leukocytic migration and infiltration of local sites in the living body. This review introduces our approaches that employ an Arg-Gly-Asp (RGD) fiber-mutant adenovirus vector encoding the chemokine or chemokine receptor gene in cancer immunotherapy.

Expression and regulation of CCL18 in synovial fluid neutrophils of patients with rheumatoid arthritis

Rheumatoid arthritis (RA) is characterized by the recruitment of leukocytes and the accumulation of inflammatory mediators within the synovial compartment. Release of the chemokine CCL18 has been widely attributed to antigen-presenting cells, including macrophages and dendritic cells. This study investigates the production of CCL18 in polymorphonuclear neutrophils (PMN), the predominant cell type recruited into synovial fluid (SF). Microarray analysis, semiquantitative and quantitative reverse transcriptase polymerase chain reaction identified SF PMN from patients with RA as a novel source for CCL18 in diseased joints. Highly upregulated expression of other chemokine genes was observed for CCL3, CXCL8 and CXCL10, whereas CCL21 was downregulated. The chemokine receptor genes were differentially expressed, with upregulation of CXCR4, CCRL2 and CCR5 and downregulation of CXCR1 and CXCR2. In cell culture experiments, expression of CCL18 mRNA in blood PMN was induced by tumor necrosis factor α, whereas synthesis of CCL18 protein required additional stimulation with a combination of IL-10 and vitamin D3. In comparison, recruited SF PMN from patients with RA were sensitized for CCL18 production, because IL-10 alone was sufficient to induce CCL18 release. These results suggest a release of the T cell-attracting CCL18 by PMN when recruited to diseased joints. However, its production is tightly regulated at the levels of mRNA expression and protein synthesis.

Control of cell migration in the development of the posterior lateral line: antagonistic interactions between the chemokine receptors CXCR4 and CXCR7/RDC1

BackgroundThe formation of the posterior lateral line of teleosts depends on the migration of a primordium that originates near the otic vesicle and moves to the tip of the tail. Groups of cells at the trailing edge of the primordium slow down at regular intervals and eventually settle to differentiate as sense organs. The migration of the primordium is driven by the chemokine SDF1 and by its receptor CXCR4, encoded respectively by the genes sdf1a and cxcr4b. cxcr4b is expressed in the migrating cells and is down-regulated in the trailing cells of the primordium. sdf1a is expressed along the path of migration. There is no evidence for a gradient of sdf1a expression, however, and the origin of the directionality of migration is not known.ResultsHere we document the expression of a second chemokine receptor gene, cxcr7, in the migrating primordium. We show that cxcr7 is highly expressed in the trailing cells of the primordium but not at all in the leading cells, a pattern that is complementary to that of cxcr4b. Even though cxcr7 is not expressed in the cells that lead primordium migration, its inactivation results in impaired migration. The phenotypes of cxcr4b, cxcr7 double morphant embryos suggest, however, that CXCR7 does not contribute to the migratory capabilities of primordium cells. We also show that, in the absence of cxcr4b, expression of cxcr7 becomes ubiquitous in the stalled primordium.ConclusionOur observations suggest that CXCR7 is required to provide directionality to the migration. We propose that directionality is imposed on the primordium as soon as it comes in contact with the stripe of SDF1, and is maintained throughout migration by a negative interaction between the two receptors.

Pushing it back. Dating the CCR5–32 bp deletion to the Mesolithic in Sweden and its implications for the Meso\Neo transition

Genetic variation in the chemokine receptor gene CCR5 has received considerable scientific interest during the last few years. Protection against HIV-infection and AIDS, together with specific geographic distribution are the major reasons for the great interest in CCR5 32bp deletion. The event for the occurrence of this mutation has been postulated by coalescence dating to the 14th century, or 5000 BP. In our prehistoric Swedish samples we show that the frequency of 32pb deletion in CCR5 in the Neolithic population does not deviate from the frequency in a modern Swedish population, and that the deletion existed in Sweden already during the Mesolithic period.

Polymorphisms in CCL2&CCL5 chemokines/chemokine receptors genes and their association with diseases.

Chemokines and chemokine receptors are major mediators of leukocyte trafficking into the sites of the immune response. They participate in defence against microbial infection, in Th1/Th2 polarization of the immune response, allograft rejection and angiogenesis/angiostasis as well as in tumorigenesis and metastasis. To date, several functional polymorphisms of chemokine and chemokine receptor genes have been discovered that are able to deregulate chemokine system and, therefore, they may interfere with the pathogenesis of a large number of inflammatory and other diseases. In this review we focus on the known polymorphisms of two chemokines: CCL2, CCL5 and their corresponding receptors (CCR2, CCR5) and we also discuss their associations with susceptibility and progression to selected immune-mediated diseases. Based on relevant literature this article gives a short overview of case-control and family studies regarding effect of the genetic factors on diseases such as coronary artery disease, systemic lupus erythematosus, diabetes mellitus, lung diseases and others. Recent advance in the identification of chemokine genetic background of the diseases could provide opportunity for pharmacological treatment. However, we need more information about posttranscriptional events to understand functional relevance of polymorphisms and to discovery new avenues to blocking disease development.

Recurrent CXCR4 sequence variation in a girl with WHIM syndrome

WHIM (warts-hypogammaglobulinemia-infections-myelokathexis) syndrome is a recently described primary immunodeficiency disorder caused by mutation of the CXCR4 chemokine receptor gene. We report here of a 6.5-yr-old girl with bacterial infections, severe chronic neutropenia, and hypogammaglobulinemia. Sequencing the CXCR4 gene revealed a c.1013C > G sequence variant suggesting WHIM syndrome. Recurrent c.1013C > G sequence variant of the CXCR4 gene resulting in p.S338X truncation mutation of this chemokine receptor protein is first reported here.

Polymorphism of chemokine receptor gene CCR5 in multiple sclerosis patients and in healthy subjects in the Siberian region

Multiple sclerosis is chronic inflammatory disease of the central nervous system in the development of which chemokines of the type Tx1 play the leading role. Chemokines and their receptors participate in the development of multiple sclerosis as a result of drawing immune cells into central nervous system. Mutation of CCR5 delta32 decreases functional activity of the appropriate receptor on cellular surface and thus can reduce migration of leucocytes into foci of injury. Aimed at studying the role of mutation in multiple sclerosis, we compared frequency of gene type CCR5 in peripheral mononuclears of 102 multiple sclerosis patients and in 136 healthy subjects. The results obtained allow to conclude that polymorphism of chemokine receptor gene CCR5del32 is not a leading factor in the susceptibility to multiple sclerosis in the studied population.

The first non-mammalian CXCR3 in a teleost fish: Gene and expression in blood cells and central nervous system in the grass carp ( Ctenopharyngodon idella)

A novel fish chemokine receptor gene, chemokine (C–X–C motif) receptor 3 (CXCR3)-like was isolated from the grass carp Ctenopharyngodon idella, with its full-length genomic sequence. The cDNA of grass carp CXCR3-like (gcCXCR3-like) consists of 1261 bp with a 49 bp 5′-UTR and a 189 bp 3′-UTR. An open reading frame of 1023 bp encodes a 341-amino acid peptide, with seven transmembrane helices. The deduced amino acid sequence showed the same sequence identities (37.8%) with its counterparts in goat and human. The gcCXCR3-like gene consists of two exons, with one intervening intron, spaced over approximately 2 kb of genomic sequence. Phylogenetic analyses clearly demonstrated that the gcCXCR3-like resembles the CXCR3s of other vertebrates. Real-time PCR analysis showed that gcCXCR3-like was expressed in all tested organs except heart and the expression level of gcCXCR3-like was highest in brain. Flow cytometric analyses showed the positive rate of labelled leukocytes from the healthy grass carp was 17.3%, and the labelled leukocytes were divided into three types by cell sorting. Immunohistochemical localization revealed that gcCXCR3-like expressed in whole brain regions including cerebel, diencephalon, medulla oblongata, optic lobe, and rhinencephalon, and that the labelled leukocytes are actually populations of monocyte and/or phagocyte, lymphocyte and the granulocyte. It is considered that fish CXCR expression and their function may need to be investigated in both nervous and immune systems.

Functional Analysis of the Chemokine Receptor CCR3 on Airway Epithelial Cells

The function of chemokine receptors on structural cells is only partially known. We previously reported the expression of a functional CCR3 receptor on airway epithelial cells (EC). We speculated that CCR3 might drive wound repair and expression of inflammatory genes in epithelium. The human airway EC lines BEAS-2B, 16-HBE, and primary bronchial EC were used to test the effect of in vitro challenge with the CCR3 ligands CCL11/eotaxin, CCL24/eotaxin-2, or CCL26/eotaxin-3 on 1) wound repair, using an established wound model; 2) cell proliferation and chemotaxis, using specific fluorometric assays; and 3) gene expression, using pathway-specific arrays for inflammatory and profibrotic cytokines, chemokines, and chemokine receptor genes. Agonist specificity was tested by cell pretreatment with an AstraZeneca CCR3 antagonist (10(-8) - 10(-6) M). CCL24 challenge significantly accelerated epithelial wound closure, with similar effects exerted by CCL11 and CCL26. This effect was time dependent, submaximal at 1 nM, and comparable in potency to epidermal growth factor. CCL24 induced a concentration-dependent increase in EC proliferation and chemotaxis, with significant effects observed at 10 nM. The AstraZeneca compound selectively inhibited these CCL24-mediated responses. CCL11 induced the up-regulation of several profibrogenic molecules such as fibroblast growth factor 1 and 5 and of several CC and CXC chemokines. Epithelial immunostaining for CCR3 was stronger in bronchial biopsies of asthmatics displaying marked inflammatory changes than in nondiseased samples. Epithelial CCR3 participates in key functions for wound repair, amplifies the expression of profibrogenic and chemokine transcripts, and appears up-regulated in inflamed asthmatic airways.

Impact of Inversion of the CD4/CD8 Ratio on the Natural History of HIV-1 Infection

HIV-1 infection is characterized by an inverted CD4/CD8 T-cell ratio, but the distribution of inversions over time after seroconversion and whether delay of inversion is associated with a favorable prognosis are not known. T-cell counts and clinical outcomes among men in the Multicenter AIDS Cohort Study who had incident HIV-1 infection before December 31, 1995 were analyzed by Kaplan-Meier and Cox proportional hazards methods. Results were also analyzed by time-dependent multivariate methods to adjust for CD4 lymphocyte counts, viral loads, age, race, and polymorphisms in host chemokine receptor genes (CCR5-Delta32 and CCR2-64I). Among 424 cases whose date of seroconversion was known to within +/-4.5 months, 317, 52, and 55 inverted their CD4/CD8 ratio within less than 1, 1 to 2, and more than 2 years of seroconversion, respectively. Longer time to inversion was significantly associated with longer time to AIDS, even after adjusting for CD4 lymphocyte count and viral load at the first seropositive visit and over the first 3 seropositive visits. Of the 6 seroconverters who had more than 500 CD4 lymphocytes 10 years after seroconversion without receiving highly active antiretroviral therapy, 5 took more than 2 years to invert their CD4/CD8 ratio. Time from HIV-1 seroconversion to inversion of the CD4/CD8 ratio independently predicted time to AIDS. Early measurements of the CD4/CD8 ratio until inversion occurs may identify people likely to become long-term nonprogressors or slow progressors, thus facilitating detailed studies of the mechanism of HIV-1 disease progression.

Gene Polymorphisms in CCR5, CCR2, CX3CR1, SDF-1 and RANTES in Exposed but Uninfected Partners of HIV-1 Infected Individuals in North India

Repeated exposure to human immunodeficiency virus (HIV) does not always result in infection. Understanding the mechanisms that give protection against progressive infection with HIV may help in the development of a vaccine. In order to determine the influence of host genetic factors on HIV resistance, we studied 35 exposed but uninfected (EU) partners of HIV-1 infected individuals for polymorphisms in multiple chemokine and chemokine receptor genes and compared the results with those for 75 HIV-1 seronegative normal healthy controls (HC) and 50 HIV infected controls. There was no association between CCR5-Delta32, CCR2-64I, CX3CR1-280 M, CX3CR1-249I, SDF-3'A, RANTES-28G and RANTES-403A polymorphisms and susceptibility against HIV in our cohort of EU individuals. An increased frequency of SDF-1 3'A and RANTES-403A genotypes was present in EU individuals but the difference was not statistically significant when compared to healthy and HIV infected controls. These observations suggest that mechanisms other than genetic mutations of these genes might be responsible for resistance to HIV infection in these individuals.

Chemokines involved in protection from colitis by CD4+CD25+ regulatory T cells

Chemokines are small proteins involved in the direction of migration of immune cells both during normal homeostasis and inflammation. Chemokines have been implicated in the pathology of many different inflammatory disorders and are therefore appealing therapeutic targets. Using a chemokine/chemokine receptor-specific gene expression profiling system of 67 genes, the authors have determined the expression profile of chemokine and chemokine receptor genes in the rectum of colitic mice and in mice that have been protected fromcolitis by CD4CD25 regulatory T cells. In mice protected from colitis, the authors found down regulation of the mRNA expression of the inflammatory chemokine receptors CCR1 and CXCR3 and their ligands CXCL9, CXCL10, CCL5, and CCL7. Also the transcripts for CCR9, CCL25, CCL17, and CXCL1 are found down regulated in protected compared with colitic animals. In addition, the authors' results suggest that CCL20 is used by CCR6 regulatory T cells in the complex process of controlling colitis because transcripts for this chemokine were expressed to a higher level in protected animals. The chemokine pathways identified in the present study may be of importance for the development of new targets for anti-inflammatory treatment strategies in human inflammatory bowel disease.

Using Mutual Information to Measure the Impact of Multiple Genetic Factors on AIDS

Since the discovery of the 32-base-pair deletion in the CCR5 chemokine receptor gene (CCR5-Delta32) and its effect on HIV-1 infection and AIDS progression, many genetic factors affecting AIDS have been identified. Here we quantify the impact of 13 of these factors on AIDS progression using a new statistic based on the mutual information between causal factors and disease, the explained fraction. The influence of causal factors on disease is commonly measured by the attributable fraction statistic, but the attributable fraction is a poor measure of the extent to which a factor explains disease because it considers only whether a factor is necessary, not whether it is sufficient. The definition of the explained fraction, which is analogous to R or the explained variation for regression models, extends naturally to multiple factor levels. Because the explained fraction is approximately additive, it can be used to estimate how much of epidemiological data is explained by known genetic or environmental factors, and conversely how much is yet to be explained by unknown factors. We show that 13 genetic factors can cumulatively explain 9% of slow progression to AIDS, an effect comparable to the effect of smoking on lung cancer.

Host polymorphism in steps of the HIV-1 lifecycle after entry and other genetic variants influencing HIV-1 pathogenesis

Dominant host factors modifying the susceptibility to HIV-1 include diversity in the major histocompatibility complex class I, and alleles of chemokine and chemokine receptor genes. Additional host factors, particularly those determining cell permissiveness to viral replication, are expected to play a significant role in HIV-1 pathogenesis. A growing number of publications (n = 32) propose new variants (n = 27) modifying HIV-1 susceptibility in genes (n = 17) needed for the viral lifecycle, in antiviral innate defense, and in a number of soluble and membrane proteins. Although there are multiple publications describing putative associations of host genetic variants and susceptibility to HIV-1, most reports are yet to be confirmed by subsequent publications, or have led to conflicting data among laboratories.

Analysis of CC chemokine receptor 5 and 2 polymorphisms and renal transplant survival

Chronic rejection is an immune process leading to graft failure. By regulating the trafficking of leukocytes, chemokines and chemokine receptors are thought to be one of the reasons causing acute renal rejection (ARE), which increases the possibility of chronic rejection and organ destruction. This study was designed to investigate, in the Turkish population, an association of chemokine receptor genetic variants, CCR2V641, CCR5-59029-A/G, CCR5-Delta32 and acute renal rejection after renal transplant surgery. We carried out our study in 85 Turkish renal transplant patients (45 men, 40 women; mean age 39 +/- 2 years) by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) techniques. We found no significant difference in the incidence of rejection among patients possessing or lacking CCR5-Delta32. For the groups with and without acute renal rejection, we found a significant difference between the groups in A and G allele distribution in both CCR2V641and CCR559029 gene variants (p = 0.003 and p = 0.003, respectively). According to our findings, the risk of acute rejection in renal transplantation may be associated with genetic variation in the chemokine receptor genes CCR5-59029 and CCR2V641 in Turkey, and studies on these gene polymorphisms could be an ideal target for future interventions intended to prevent renal transplant loss.

The DNA sequence, annotation and analysis of human chromosome 3

After the completion of a draft human genome sequence, the International Human Genome Sequencing Consortium has proceeded to finish and annotate each of the 24 chromosomes comprising the human genome. Here we describe the sequencing and analysis of human chromosome 3, one of the largest human chromosomes. Chromosome 3 comprises just four contigs, one of which currently represents the longest unbroken stretch of finished DNA sequence known so far. The chromosome is remarkable in having the lowest rate of segmental duplication in the genome. It also includes a chemokine receptor gene cluster as well as numerous loci involved in multiple human cancers such as the gene encoding FHIT, which contains the most common constitutive fragile site in the genome, FRA3B. Using genomic sequence from chimpanzee and rhesus macaque, we were able to characterize the breakpoints defining a large pericentric inversion that occurred some time after the split of Homininae from Ponginae, and propose an evolutionary history of the inversion.

Expression of IL-8 during Reperfusion of Renal Allografts Is Dependent on Ischemic Time

Ischemia/reperfusion injury is an inherent consequence of solid organ transplantation that increases tissue inflammation and negatively impacts organ transplant function and survival. This study investigated the expression levels of chemokine and chemokine receptor genes in living versus cadaver donor renal allografts before and after reperfusion. This study involved 39 renal transplant patients (19 cadaveric and 20 living donor). The ischemia biopsy was taken just before graft declamping and the reperfusion biopsy 30 min after declamping. Whole-cell RNA was isolated and chemokine (IL-8, CCL2/MCP-1, CXCL10/IP-10 and CCL5/RANTES) and chemokine receptor (CCR2 and CCR5) expression was tested by quantitative PCR. Just prior to declamping, ischemic cadaveric donor grafts had higher expression of CXCL10/IP-10 but not IL-8 or CCL2/MCP-1 than living donor grafts. IL-8 expression increased 50% from ischemia to reperfusion in living donor grafts but increased more than 13-fold during reperfusion of cadaver donor grafts. Increased total ischemia time induced greater IL-8 expression during reperfusion. MCP-1 expression also increased during reperfusion of living and cadaver donor grafts but differences were not observed between the two groups of grafts. RANTES, CCR2, and CCR5 expression did not change in ischemic vs. reperfusion biopsies. The expression of chemokines directing neutrophil and macrophage recruitment increases during reperfusion of living and cadaveric donor renal allografts. Expression levels of IL-8 correlate with the ischemic time imposed on the renal graft. Early tissue injury may be attenuated by strategies antagonizing chemokines directing the recruitment of neutrophils and macrophages into kidney grafts.

Differential roles for CXCR3 in CD4+ and CD8+ T cell trafficking following viral infection of the CNS

Lymphocyte infiltration into the central nervous system (CNS) following viral infection represents an important component of host defense and is required for control of viral replication. However, the mechanisms governing inflammation in response to viral infection of the CNS are not well understood. Following intracranial (i.c.) infection of susceptible mice with mouse hepatitis virus (MHV), mice develop an acute encephalomyelitis followed by a chronic demyelinating disease. The CXC chemokine ligand 10 (CXCL10) is expressed following MHV infection and signals T cells to migrate into the CNS. The functional contribution of the CXCL10 receptor CXCR3 in host defense and disease in response to MHV infection was evaluated. The majority of CD4+ and CD8+ T cells infiltrating the CNS following MHV infection express CXCR3. Administration of anti-CXCR3 antibody reduced CD4+ T cell infiltration (p<or=0.05), while CD8+ T cell trafficking was not affected. Anti-CXCR3 treatment during chronic disease correlated with improved motor skills and reduced demyelination. The selective effect of anti-CXCR3 treatment on CD4+ T cells was not the result of either reduced proliferation or modulation in chemokine receptor gene expression. Therefore, CXCR3 signaling has a non-redundant role in T cell subset trafficking in response to viral infection.

The WHIM syndrome shows a peculiar dysgranulopoiesis: myelokathexis

A 17-year-old boy had been born at term after an uneventful pregnancy to non-consanguineous parents. His siblings and parents were well. He had experienced numerous upper respiratory tract infections since birth, which had caused pulmonary atelectasia requiring surgical removal of the affected lobe. He had suffered recurrent herpetic peribuccal infection. Warts had appeared on his hands at 6 years of age and extended gradually to the elbows, arms, legs, knees and feet. Pancytopenia was first documented at the age of 1 month. White blood cell counts varied from 1·9 to 3·9 × 109/l with neutrophil counts of 0·9–2·8 × 109/l. There was no cyclic pattern of neutropenia. His haemoglobin concentration ranged between 10 and 12 g/dl and the platelet count was 47–127 × 109/l. Blood smears showed abnormal neutrophils with condensed nuclei connected by long, stringy filaments. The bone marrow was hypercellular with an increased proportion of mature myeloid cells (left). Many neutrophils had bisegmented nuclei with dense pyknotic lobes connected by long filaments leading to bizarre forms, such as ‘eyeglasses’ or ‘clover leaf’ (right). Occasionally, these filaments were twisted around each other. Some eosinophils showed cytoplasmic vacuolation. No significant morphological abnormalities were observed in the other cell lineages. Folic acid and vitamin B12 levels were normal. Immunological investigation showed severe combined immunodeficiency. Both B- and T-cell subpopulations were reduced, particularly CD4+ T cells. T-cell responses to vaccine antigens were moderately affected. Global hypogammaglobulinaemia was observed (IgG < 6 g/l; normal levels of IgG2 and IgG3). No antibodies to leucocytes or platelets were detected and karyotype analysis was normal. Monthly treatment with gammaglobulins and filgrastim was initiated when the child was 7 years of age, producing a subsequent decrease in the rate of infections and an increased neutrophil count (>1 × 109/l). The patient presented the full spectrum of findings described in the WHIM syndrome, a rare immunodeficiency disorder characterised by warts, hypogammaglobulinaemia, infections and myelokathexis. Myelokathexis is characterised by a prolonged retention of neutrophils in the bone marrow compartment leading to neutropenia, despite hyperplasia of bone marrow myeloid cells, and degenerative changes in mature neutrophils. The observation of these morphologic features was strongly suggestive of myelokathexis and is helpful in the diagnosis of WHIM syndrome. This syndrome is caused by the mutation of a chemokine receptor gene, leading to production of the mutant CXCR4 protein that causes abnormal aptoptosis and migratory function, thought to be related to the cause of chronic leucopenia.