Differential expression of the chemokine receptors by the Th1- and Th2-type effector populations within circulating CD4+ T cells

The in vitro studies have proposed that human Th1 cells favor expression of CXCR3 or CCR5, whereas Th2 cells favor CCR3 and CCR4. In this study, the in vivo relevance of expression of these chemokine receptors on Th cells was investigated in patients with atopic dermatitis (AD) as the Th2-dominated disorder and nonatopic normal individuals. Flow-cytometric analysis using monoclonal antibodies against CXCR3, CCR5, CCR3, and CCR4 disclosed that a substantial proportion of memory (CD45RO+) CD4+ T cells in the blood of AD and normal patients expressed CXCR3, CCR5, or CCR4, but expression of CCR3 on these cells was negligible. Stimulation studies combined with intracellular cytokine staining revealed that the cells capable of producing Th2 cytokines, such as interleukin-4 (IL-4), IL-5, and IL-13, were restricted to the CCR4-expressing population within memory CD4+ T cells. Concerning Th1 cytokine production, interferon-gamma (IFN-gamma)-producing cells resided exclusively in CXCR3-expressing memory CD4+ T cells, although IFN-gamma production was found in both memory CD4+ T cells with and without CCR5 expression. We observed that CCR4-expressing memory CD4+ T cells in the blood were more increased in AD patients as compared with normal patients, whereas CXCR3-expressing memory CD4+ T cells were present in a lower frequency in AD than seen in normal patients. These results suggest that CXCR3 and CCR4, but not CCR5 or CCR3, appear to serve as the useful markers for identification of circulating Th1 and Th2 effector populations.     

Chemokine receptors that mediate B cell homing to secondary lymphoid tissues are highly expressed in B cell chronic lymphocytic leukemia and non-Hodgkin lymphomas with widespread nodular dissemination

B cell neoplasms present heterogeneous patterns of lymphoid organ involvement, which may be a result of the differential expression of chemokine receptors. We found that chemokine receptor (CCR)7, CXC chemokine receptor (CXCR)4, or CXCR5, the main chemokine receptors that mediate B cell entry into secondary lymphoid tissues and their homing to T cell and B cell zones therein, were highly expressed in B malignancies with widespread involvement of lymph nodes. Conversely, those pathologies with little or no nodular dissemination showed no expression to very low levels of CCR7 and CXCR5 and low to moderate levels of CXCR4. These findings provide evidence for the role of CCR7, CXCR4, and CXCR5 in determining the pattern of lymphoid organ involvement of B tumors. Functional studies were performed on B malignancies expressing different levels of CCR7, CXCR5, and CXCR4. Multiple myeloma (MM) cells did not express CCR7 nor CXCR5 and did not migrate in response to their ligands; a moderate expression of CXCR4 on MM cells was accompanied by a migratory response to its ligand, CXCL12. By contrast, cells from B cell chronic lymphocytic leukemia (B-CLL) expressed the highest levels of these chemokine receptors and efficiently migrated in response to all ligands of CCR7, CXCR4, and CXCR5. In addition, the migration index of B-CLL cells in response to both of the CCR7 ligands correlated with the presence of clinical lymphadenopathy, thus indicating that the high expression of functional chemokine receptors justifies the widespread character of B-CLL, representing a clinical target for the control of tumor cell dissemination.     

Duration of sample storage dramatically alters expression of the human immunodeficiency virus coreceptors CXCR4 and CCR5

Expression of the chemokine receptors CXCR4 and CCR5 was monitored using EDTA-anticoagulated whole blood held for different time periods prior to fluorescent-antibody staining. When left overnight CXCR4 expression on leukocytes was substantially increased, whereas CCR5 expression was reduced. The results were similar when heparin and acid-citrate-dextrose were used as anticoagulants.     

HIV-1协同受体CXCR4、CCR5及相关趋化因子SDF-1在胎盘的表达

目的：研究HIV-1协同受体CXCR4、CCR5及CXCR4的特异性配体SDF-1在人胎盘组织的表达，探索HIV-1子宫内垂直传播的分子机制。方法：半定量RT-PCR检测早、中、晚孕期胎盘及早孕滋养细胞CXCR4、CCR5 mRNA水平；免疫组化和免疫细胞化学检测早孕胎盘及原代培养滋养细胞CXCR4、CCR5蛋白表达；原位杂交及免疫组化分析SDF-1在早孕胎盘的表达；ELISA测定滋养细胞SDF-1的动态分泌水平。结果：各孕期胎盘表达CXCR4及CCR5 mRNA；CXCR4蛋白定位于滋养细胞，而CCR5蛋白定位于绒毛基质中。滋养细胞可转录并翻译SDF-1，且能分泌可溶性SDF-1。结论：滋养细胞同时表达CXCR4及SDF-1，SDF-1可能通过降调CXCR4而拮抗X4-HIV-1感染胎儿细胞；R5-HIV-1或许能通过滋养层裂隙感染CCR5^#基质细胞和/或Hotbauer细胞，从而发生子宫内垂直传播。     

Kinetics and expression patterns of chemokine receptors in human CD4+ T lymphocytes primed by myeloid or plasmacytoid dendritic cells

We investigated the kinetics of expression of 12 chemoattractant receptors as a function of cell division following priming of human naive CD4+ T cells by different populations of dendritic cells (DC) and under conditions favoring Th1 or Th2 differentiation. Two chemokine receptors, CXCR3 and CXCR5, were rapidly up-regulated following T cell activation by either monocyte-derived DC, myeloid DC (mDC) or plasmacytoid DC (pDC). While CXCR5 expression was transient, expression of CXCR3 at advanced cell divisions was dependent on differentiation, being expressed at high levels on Th1 cells. Several other receptors (CCR2, CCR3, CCR4, CCR5, CXCR6 and CRTh2) were acquired progressively as a function of cell division and in a fashion that was influenced by polarizing cytokines. The Th2-associated chemoattractant receptors CRTh2 and CCR3 were up-regulated with slower kinetics compared to the Th1-associated receptors CXCR3 and CXCR6, consistent with a different kinetics and efficiency of polarization. Moreover, CCR4 and CXCR6 were preferentially induced in T cells activated by mDC and pDC, respectively. Finally, CXCR5 and CCR7 were also rapidly and transiently up-regulated in memory T cells following TCR stimulation. These results indicate a complex chemokine receptor regulation dependent on both T cell activation and differentiation state. In addition, they reveal the existence of DC-specific cues for the regulation of T cell migratory capacity.     

CCR5 and CXCR4 expression on memory and naive T cells in HIV-1 infection and response to highly active antiretroviral therapy

OBJECTIVE: To measure CCR5 and CXCR4 chemokine receptor expression on CD4 and CD8 T cells in HIV-1 infection and to relate levels to the distribution of CD45RO memory and CD45RA-naive subsets, measures of disease activity, and response to highly active antiretroviral therapy (HAART). DESIGN: Fourteen untreated HIV-1-infected patients, 18 patients at 3-to 4-weeks after beginning HAART, and 35 uninfected control subjects were studied. METHODS: Four-color cytofluorometry with appropriate conjugated monoclonal antibodies (mAbs) was performed to define CD45RA and CD45RO subsets of CD4 and CD8 T cells and measure their expression of CCR5, CXCR4, and CD38. RESULTS: HIV-1-infected patients had higher CCR5 levels and lower CXCR4 levels on CD4 and CD8 T cells and their CD45RO/CD45RA subsets than control subjects did. However, CCR5 elevation was statistically significant only for CD4 T cells and their subsets, and CXCR4 depression was significant for CD8 T cells and their subsets (and for CD4:CD45RO cells). The elevation of CCR5 and depression of CXCR4 were not due to shifts in CD45RO/CD45RA subset proportions but to upregulation or downregulation within the subsets. CCR5 elevation on CD4 T cells was significantly restored toward normal by HAART, but the CXCR4 depression was not. CCR5 expression but not CXCR4 expression correlated with other measures of immunodeficiency (CD4 T-cell levels), active infection (viral load), and cellular activation (CD38). CONCLUSIONS: CCR5 elevation is a concomitant of immune activation and viral replication that occurs in HIV-1 infection, but the relation of CXCR4 depression to severity of infection, disease progression, and response to therapy remains undefined.     

Immunohistochemical analysis of CCR2, CCR3, CCR5, and CXCR4 in the human brain: potential mechanisms for HIV dementia

The CXC chemokine receptor CXCR4 was the first molecule identified as a coreceptor working in conjunction with CD4 to mediate cellular entry for the human immunodeficiency virus (HIV-1). Since that original discovery, 11 other seven-mtransmembrane domain molecules, many of which are chemokine receptors, have been shown to facilitate HIV entry into cells. These include CCR5, CCR3, CCR2, CCR1, CCR8, CX3CR1, STRL33 (BONZO), GPR15 (BOB), GPR1, US28, and APJ. In studies done by this and other labs, CCR3, CCR5, and CXCR4 have been identified in CNS microglia and several laboratories, including ours, have shown that CXCR4 is expressed in neurons. Neuronal expression of CCR2, CCR3, and CCR5 has been less consistent. We performed a semiquantitative immunohistochemical analysis of the expression of CCR2, CCR3, CCR5, and CXCR4 in 23 regions of the brain and in two sections of the spinal cord. Hippocampal neurons were positive for CCR2, CCR3, and CXCR4, but not for CCR5. In other regions of the brain, neurons, and glial cells reacted with anti-CCR2, anti-CCR3, and anti-CXCR4 antibodies, whereas only glial cells (primarily microglia) were positive for CCR5. The areas of highest expression, however, seem to be subcortical regions and the limbic system. The limbic system plays a key role in memory, and the presence of CXCR4-which can bind the viral envelope protein gp120-min a subset of neurons from this system may play a role in the development of HIV-related dementia.     

Selective recruitment of CXCR3+ and CCR5+ CCR4+ T cells into synovial tissue in patients with rheumatoid arthritis

The inflamed synovial tissue (ST) of rheumatoid arthritis (RA) is characterized by the selective accumulation of interferon gamma-producing Th1-type CD4+ T cells. In this study, we investigated whether the predominance of Th1-type CD4+ cells in the ST lesion is mediated by their selective recruitment through Th1 cell-associated chemokine receptors CXCR3 and CCR5. The lymphocyte aggregates in the ST of RA contained a large number of CD4+ T cells, which mostly expressed both CXCR3 and CCR5, but not CCR4. In contrast, the frequencies of CD4+ and CD8+ T cells expressing CXCR3 and CCR5 in the blood were significantly decreased in RA patients, compared with healthy controls (HC), although there was no difference in the frequencies of CCR4-expressing CD4+ and CD8+ T cells between RA and HC. CXCR3, CCR5, and CCR4 expression in blood CD4 + T cells and CXCR3 expression in CD8+ T cells were increased after interleukin-15 (IL-15) stimulation. Therefore, the distribution of Th1-type CD4+ T cells into the ST from the blood in RA may be associated with the local expression of chemokines, both CXCR3 and CCR5 ligands, and IL-15 may play a role in enhancing these chemokine receptors on CD4+ T cell infiltrates.     

Predominant intracellular expression of CXCR4 and CCR5 in purified primary trophoblast cells from first trimester and term human placentae

PROBLEM: The aim of the present study was to define the expression of CXCR4 and CCR5 on non-cultured non-stimulated primary human trophoblast cells (TCs) immediately after their immunopurification. METHOD OF STUDY: We have evaluated by flow cytometric analysis and immunofluorescence, highly purified primary TCs prepared from first trimester (8.2 +/- 0.3 weeks, n = 15) and term (Caesarean section, n = 10) placentae for the cell surface and intracellular expression of CXCR4 and CCR5. RESULTS: There was a high level of individual variability for CXCR4 and CCR5 expression between trophoblast batches. In first trimester and term placentae TCs, we found a greater number of TCs preparations expressing intracellular CXCR4 than CCR5 (P < 0.05). Both receptors were predominantly localized in the intracellular compartment of TCs, whatever if isolated from first trimester or term placentae. CONCLUSIONS: The functional consequences of the predominance of CXCR4 expression and of cellular addressing are briefly discussed.     

Down-regulation of CXCR4 expression on human CD8+ T cells during peripheral differentiation

Multi-color flow cytometric analysis on human CD8(+) T cell subsets revealed that CXCR4 is predominantly expressed on CD8(+) T cells with the naive CD27(+)CD28(+)CD45RA(+) phenotype, and is down-regulated during differentiation into those with an effector phenotype. The down-regulation of CXCR4 expression during peripheral differentiation was supported by the fact that the expression of CXCR4 on CD8(+) T cells was negatively correlated with that of perforin. The analysis of CCR5, CCR7, and CXCR4 co-expression further showed that CD8(+) T cells expressing a high level of CXCR4 are CCR7(+)CCR5(-) naive or central memory subsets, and those expressing a low level of CXCR4 were included in the CCR7(-)CCR5(+/-) memory/effector and effector subsets. Epstein Barr virus-specific CD8(+) T cells, which mostly express the memory phenotype, expressed CXCR4, while human cytomegalovirus-specific CD8(+) T cells, which mostly express the effector phenotype, partially expressed this receptor, showing that the expression of CXCR4 is also down-regulated during differentiation of viral antigen-specific CD8(+) T cells. The classification of human CD8(+) T cells based on the expression of these chemokine receptors should prove useful for studies that clarify the differentiation of human CD8(+) T cells.     

早、中、晚孕期胎盘因子对人外周血淋巴细胞CD4、CCR5和CXCR4表达的影响

目的 通过研究早、中、晚孕期胎盘因子(PF)对人外周血淋巴细胞(PBLs)中CD4、CCR5和CXCR4表达的作用,探讨PF在人免疫缺陷病毒-1(HIV-1)垂直传播中的作用及其机理.方法 制备早、中、晚孕期PF.分离人外周血单个核细胞,并分别与相对浓度为25%的早、中、晚孕期PF作用,培养24 h后收集细胞,荧光抗体标记,流式细胞术检测外周血淋巴细胞(PBLs)中CD4、CCR5和CXCR4表达,以及CD4 T细胞中CCR5 细胞、CXCR4 细胞、CCR5 CXCR4 细胞所占的百分率.结果 各孕期PF均可显著降低PBLs中CCR5的表达,其中早孕期PF的作用明显强于中、晚孕期PF的作用;各孕期PF组CD4 T细胞中CCR5 细胞的百分率均显著低于对照组,早孕期PF组CD4 T细胞中CCR5 细胞的百分率明显低于中、晚孕期PF组;各孕期PF组CD4 T细胞中CCR5 CXCR4 细胞的百分率均显著低于对照组,早孕期PF组CD4 T细胞中CCR5 CXCR4 细胞的百分率显著低于晚孕期PF组.结论 各孕期PF均可显著降低PBLs中CCR5的表达,以及CD4 T细胞中CCR5 细胞和CCR5 CXCR4 细胞的百分率,早孕期PF作用最强,中、晚孕期PF效应相当,PF可能通过抑制R5病毒的人胞而具有抗R5病毒的作用,并可能在阻断HIV-1宫内感染中具有重要作用.     

HIV-1感染者淋巴细胞活化与第二受体表达的研究

目的：了解HIV－1感染者体内淋巴细胞的活化情况及表达第二受体CCR5、CXCR4的淋巴细胞活化状态，分析这些指标与疾病严重程度的关系，探讨HIV感染的免疫基础。方法：用三色标记法流式细胞术检测24例HIV－1感染者及13例健康对照的抗凝血标本，分析活化标志物HLA－DR及第二受体CCR5、CXCR4的表达等指标。结果：HIV－1感染者CD8^ T淋巴细胞的HLA－DR表达高于健康对照（P＜0．001）；HIV－1感染者表达CCR5、CXCR4的CD8^ T淋巴细胞活化明显高于健康对照（P＜0．001）；表达CCR5CD4^ 、CD8^ T淋巴细胞与表达CXCR4相比HL－DR表达均明显增高（P＜0．001）；CD4^ 、CD8^ T淋巴细胞的活化状态与CD4百分率的变化明显关系。结论：HIV－1感染者CD8^ T淋巴细胞及表达不同第二受体的CD8^ T淋巴细胞活化程度明显增高，活化程度与疾病进程相关。     

Expression and functional activity of chemokine receptors in glatiramer acetate-specific T cells isolated from multiple sclerosis patient receiving the drug glatiramer acetate

The purpose of the current study is to examine the surface expression of chemokine receptors and the chemotaxis toward the respective chemokines of glatiramer acetate (GA)-specific CD4(+) T cells isolated from the blood and the cerebrospinal fluid (CSF) of a multiple sclerosis (MS) patient. Four clones were selected, two isolated from the peripheral blood and two from the CSF. CCR4 and CXCR3 were expressed on all four clones. Both blood-derived clones also expressed CCR5 and, to a lesser extent, CCR6. Similarly, one CSF clone expressed CCR5 and CCR6. In contrast, CCR1, CCR2, CCR3, CCR7, CCR9, CCR10, CXCR1, CXCR4, CXCR5, CXCR6, and CCR6 were either expressed on few cells or were not expressed at all on all four clones examined. The expression of chemokine receptors was corroborated with the ability of the cells to respond chemotactically to the corresponding chemokines, CCL5/RANTES, CCL20/MIP-3α, CCL22/MDC and CXCL10/IP-10. Both the receptor expression and chemotaxis were reduced upon activation with PMA and ionomycin. The shared expression of chemokine receptors and the migration patterns suggest that GA-reactive cells have migrated from the blood into the CSF, and that local reactivation within the inflamed CSF may downregulate the expression of chemokine receptors and hence impede their migration intrathecally. The results may also explain the beneficial synergistic effects of combining immunosuppressive drugs with GA in MS patients.     

CCR4 is an up-regulated chemokine receptor of peripheral blood memory CD4+ T cells in Crohn's disease

Several chemokine receptors are expressed selectively on the surface of T cells depending on their polarization. The aim of this study was to characterize chemokine receptor expression in peripheral blood memory T cells in Crohn's disease (CD) and ulcerative colitis (UC), and to correlate the expression with disease activity. Peripheral blood mononuclear cells (PBMCs) were obtained from 24 patients with CD, 30 patients with UC, 24 normal controls and 10 disease controls. PBMCs were stained by anti-CCR3, CCR4, CCR5, CXCR3, CD4, CD8, CD45RO and beta 7 integrin, and the expression of the chemokine receptors were determined by flow cytometry. CCR4 expression on memory T cells was significantly lower in UC than in CD or normal controls, and that of memory CD4+ T and beta 7(high) memory CD4+ T cells was significantly higher in CD than in UC or normal controls. CCR4 expression on memory CD4+ T cells exhibited significant positive correlation with disease activity in CD, and this decreased significantly after treatment. Such a decrease was not found in the disease controls. CCR5 and CXCR3 expression on memory CD8+ T cells was significantly lower in CD than in normal controls. CXCR3 expression on beta 7(high) memory CD4+ T and CXCR3 expression on memory CD8+ T cells were lower in UC than in normal controls. These findings suggest that in peripheral blood memory T cells, chemokine receptor expression is different between CD and UC. Enhancement of CCR4 and suppression of CCR5 and CXCR3 seem to be the characteristic chemokine receptor profile in peripheral blood memory T cells of CD.     

Chemokine receptor expression profile of eosinophils at inflamed tissue sites: Decreased CCR3 and increased CXCR4 expression by lung eosinophils

BACKGROUND: To date, most studies dealing with eosinophil chemokine receptors have used eosinophils isolated from peripheral blood. During the movement of eosinophils from the peripheral blood to inflamed tissue sites, microenvironmental signals might alter their expression of chemokine receptors. However, little is known about the profile of expression of chemokine receptors by eosinophils at inflamed tissue sites in human beings. OBJECTIVE: The purpose of this study was to determine whether eosinophils that have migrated into inflamed tissues exhibit a profile of chemokine receptor expression that is qualitatively and/or quantitatively different from that of eosinophils in peripheral locations. METHODS: We studied simultaneously the expression and function of chemokine receptors in eosinophils in both bronchoalveolar lavage fluid (BALF) and peripheral blood specimens of 7 patients with eosinophilic lung diseases. RESULTS: De novo expression of CCR2, CCR4, and CCR5 was not detected at either the protein or the mRNA level. However, surface expression of CCR3 was decreased and CXCR4 was conversely increased with statistical significance in BALF eosinophils. Moreover, the changes in CCR3 and CXCR4 expression were reflected in the altered migratory response to their ligands. On the other hand, the levels of CXCR1, CXCR2, CXCR3, and CCR1 were virtually unchanged in BALF eosinophils, and these receptors did not have functional significance. CONCLUSION: Eosinophils at inflamed tissue sites exhibited an expression profile qualitatively similar to that in peripheral locations, except for decreased CCR3 and increased CXCR4 expression. Our results suggest that CCR3 is primarily and CXCR4 is cooperatively involved in eosinophil accumulation at inflamed tissue sites.     

Lack of correlation between chemokine receptor and T(h)1/T(h)2 cytokine expression by individual memory T cells

Chemokine and chemokine receptor interactions may have important roles in leukocyte migration to specific immune reaction sites. Recently, it has been reported that CXC chemokine receptor (CXCR) 3 and CC chemokine receptor (CCR) 5 were preferentially expressed on T(h)1 cells, and CCR3 and CCR4 were preferentially expressed on T(h)2 cells. To investigate chemokine receptor expression by T(h) subsets in vivo, we analyzed cytokine (IL-2, IL-4 and IFN-gamma) and chemokine receptor (CXCR3, CXCR4, CCR3, CCR4 and CCR5) mRNA expression by individual peripheral CD4(+) memory T cells after short-term stimulation, employing a single-cell RT-PCR method. This ex vivo analysis shows that the frequencies of cells expressing chemokine receptor mRNA were not significantly different between T(h)1 and T(h)2 cells in normal peripheral blood. To assess a potential role of in vivo stimulation, we also analyzed unstimulated rheumatoid arthritis synovial CD4(+) memory T cells. CXCR3, CXCR4, CCR3 and CCR5 expression was detected by individual synovial T cells, but the frequencies of chemokine receptor mRNA were not clearly different between T(h)1 and non-T(h)1 cells defined by expression of IFN-gamma or lymphotoxin-alpha mRNA in all RA patients. These data suggest that chemokine receptor expression does not identify individual memory T cells producing T(h)-defining cytokines and therefore chemokine receptor expression cannot be a marker for T(h)1 or T(h)2 cells in vivo.     

中国经采供血HIV感染长期不进展者CD4~+T淋巴细胞趋化因子受体表达研究

目的:了解中国经采供血HIV感染长期不进展者CD4+T淋巴细胞趋化因子受体表达,分析其与疾病不进展的关系。方法:收集43例经采供血HIV感染长期不进展者、82例无症状HIV感染者、35例AIDS病人及40例健康对照的抗凝全血,用流式细胞仪检测趋化因子受体CCR5、CXCR4的表达,并分析其与病毒载量、CD4+T淋巴细胞绝对值及T淋巴细胞活化的相关性。结果:长期不进展组CD4+T细胞表面CCR5的表达明显低于无症状HIV感染组及AIDS组(P0.01),与健康对照无显著差异;CD4+T细胞表面CXCR4的表达各组无显著差异。CD4+T细胞表面CCR5的表达与CD4+T细胞数量显著负相关(r=-0.498,P0.05),与病毒载量无显著相关性。CD4+T细胞表面CCR5的表达与HLA、CD38在CD4+、CD8+T细胞的表达水平显著正相关(P0.001,CD38在CD4+T细胞的表达除外),CD4+T细胞表面CXCR4的表达与HLA在CD4、CD8+T细胞的表达水平显著负相关(P0.01)。结论:HIV感染长期不进展者CD4+T细胞趋化因子受体CCR5表达维持较低水平,与疾病不进展相关。     

Hormonal and embryonic regulation of chemokine receptors CXCR1, CXCR4, CCR5 and CCR2B in the human endometrium and the human blastocyst

Chemokines are implicated in the implantation process. The aim of this study was to investigate mRNA expression and protein levels of chemokine receptors CXCR1, CXCR4, CCR5 and CCR2B in human endometrium throughout the menstrual cycle, during HRT and in the human blastocyst. The regulation of chemokine receptors in the endometrial epithelium was also studied using an in-vitro model for the apposition phase of human implantation. We found up-regulation of endometrial CXCR1 mRNA (419-fold increase), CCR5 mRNA (612-fold increase) and CCR2B mRNA (657 fold-increase) during the luteal phase peaking in the pre-menstrual endometrium. CXCR4 mRNA levels presented a specific although modest (18-fold increase) up-regulation during the implantation window. These findings were corroborated at the protein level in natural and HRT cycles. Immunoreactive CCR5 and CCR2B receptors were detected in human blastocysts whereas CXCR4 and CXCR1 were not present. Chemokine receptors in cultured endometrial epithelial cells showed an up-regulation and polarization of CXCR1, CXCR4 and CCR5 receptors when a human blastocyst was present. The specific distribution and regulation of chemokine receptors in the endometrial epithelium and the human blastocyst suggest a possible implication of these receptors in the apposition and adhesion phases of human implantation.