Distinct signatures of B-cell homeostatic and activation-dependent chemokine receptors in the development and progression of extragastric MALT lymphomas

Chemokine receptors mediate migration and activation of lymphocytes through binding of their ligands. Recent studies have revealed important contributions of chemokine receptors to the development, progression, and dissemination of haematopoietic neoplasms. Because the chemokine receptor expression profile in extragastric MALT lymphoma is unknown, we performed a comprehensive study on tissue samples of parotid glands, parotid glands affected by Sjögren syndrome, extragastric MALT lymphoma, and extranodal diffuse large B‐cell lymphoma (eDLBCL) originating from MALT lymphoma (transformed MALT lymphoma). By investigating the expression of 19 chemokine receptors by real‐time PCR using a semi‐quantitative approach and of four chemokine receptors (CCR1, CCR5, CXCR6, and XCR1) by immunohistochemistry, we show that the chemokine receptor expression profiles of extragastric MALT lymphomas differ substantially from those of extranodal DBLCL, with lower expression of CCR1, CCR8, and CXCR3, and the absence of expression of CX3CR1 and XCR1 in eDLBCL. Expression of CCR6, CCR7, CXCR3, CXCR4, and CXCR5, responsible for B‐cell homing to secondary lymphoid tissue, was detected in both B‐cell malignancies. Expression of CCR4 was just detected in trisomy 3‐positive MALT lymphoma cases. Comparing gastric with extragastric MALT lymphomas, up‐regulation of CXCR1 and CXCR2 accompanied by down‐regulation of CCR8 and CX3CR1 and loss of XCR1 expression in extragastric MALT lymphomas appear to be key determinants for the site of origin of MALT lymphomagenesis. Our results support a model of stepwise progression of extragastric MALT lymphoma from a non‐neoplastic event to Sjögren syndrome, to MALT lymphoma, and finally to overt eDLBCL, guided by differentially expressed B‐cell homeostatic and activation‐dependent chemokine receptors and their ligands. Copyright © 2008 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Rapid and coordinated switch in chemokine receptor expression during dendritic cell maturation

Dendritic cells (DC) migrate into inflamed peripheral tissues where they capture antigens and, following maturation, to lymph nodes where they stimulate T cells. To gain insight into this process we compared chemokine receptor expression in immature and mature DC. Immature DC expressed CCR1, CCR2, CCR5 and CXCR1 and responded to their respective ligands, which are chemokines produced at inflammatory sites. Following stimulation with LPS or TNF-α maturing DC expressed high levels of CCR7 mRNA and acquired responsiveness to the CCR7 ligand EBI1 ligand chemokine (ELC), a chemokine produced in lymphoid organs. Maturation also resulted in up-regulation of CXCR4 and down-regulation of CXCR1 mRNA, while CCR1 and CCR5 mRNA were only marginally affected for up to 40 h. However, CCR1 and CCR5 were lost from the cell surface within 3 h, due to receptor down-regulation mediated by chemokines produced by maturing DC. A complete down-regulation of CCR1 and CCR5 mRNA was observed only after stimulation with CD40 ligand of DC induced to mature by LPS treatment. These different patterns of chemokine receptors are consistent with “inflammatory” and “primary response” phases of DC function.     

Changing responsiveness to chemokines allows medullary plasmablasts to leave lymph nodes

During T cell-dependent antibody responses lymph node B cells differentiate either to plasmablasts that grow in the medullary cords, or to blasts that proliferate in follicles forming germinal centers. Many plasmablasts differentiate to plasma cells locally, but some leave the medullary cords and migrate to downstream lymph nodes. To assess the basis for this migration, changes in the responsiveness of B cells to a range of chemokines have been studied as they differentiate. Naive B cells express high levels of CCR6, CCR7, CXCR4 and CXCR5. When activated B cells grow in follicles the expression of these chemokine receptors and the responsiveness to the respective chemokines is retained. During the extrafollicular response, plasmablast expression of CXCR5 and responsiveness to B-lymphocyte chemoattractant (CXCR5) as well as to secondary lymphoid tissue chemokine (CCR7) and stromal cell-derived factor (SDF)-1 (CXCR4) are lost while a weak response towards the CCR6 chemokine LARC is maintained. Despite losing responsiveness to SDF-1, extrafollicular plasmablasts still express high levels of CXCR4 on the cell surface. These results suggest that the combined loss of chemokine receptor expression and of chemokine responsiveness may be a necessary prerequisite for cells to migrate to the medullary cords and subsequently enter the efferent lymph.     

Changes in chemokines and chemokine receptor expression on tonsillar B cells upon Epstein–Barr virus infection

Chemokines and chemokine receptors are likely to play important roles in the pathogenesis of Epstein–Barr virus (EBV) -associated disease. The primary EBV infection occurs in the oropharynx where the virus infects mainly tonsillar B cells. We have previously shown that CXCR4 expression on tonsillar B cells is modulated by EBV. Here, CXCR5 and CCR7 expression, which is important for migration into lymphoid tissue, was followed for 14 days after EBV infection of tonsillar B cells. Early after infection (2 days) there were only minor changes in CXCR5 and CCR7 expression. However, at day 7 the expression of CXCR5, as well as of CCR7, was decreased and by day 14 these molecules were no longer present at the cell surface. Furthermore, EBV infection affects the chemotactic response to CXCL13 and CCL21 (the ligands for CXCR5 and CCR7, respectively) with a reduction of ligand-induced migration at day 2. Using gene expression profiling, we identified an additional set of chemokines and chemokine receptors that were changed upon EBV infection in comparison with non-infected tonsillar B cells. In particular, messenger RNA expression for CCR9 and the complement receptor C5AR1 was increased. Both receptors mediate homing to mucosal tissue. The alterations of the expression of these molecules may lead to retention of EBV-infected tonsillar B cells in the interfollicular region of the tonsil.     

PEG10 Activation by Co-Stimulation of CXCR5 and CCR7 Essentially Contributes to Resistance to Apoptosis in CD19^＋CD34^＋ B Cells from Patients with B Cell Lineage Acute and Chronic Lymphocytic Leukemia

We investigated CD19~+CD34~+ and CD19~+CD34 B cells from cord blood (CB) and typical patients with B celllineage acute and chronic lymphocytic leukemia (B-ALL and B-CLL) in terms of expression and functions ofCXCR5/CXCL13 and CCR7/CCL19.CXCR5 and CCR7 were selectively frequent expressed on B-ALL,B-CLLand CB CD19~+CD34~+ B cells,but not on CD19~+CD34 B cells.Instead of induction of impressive chemotacticresponsiveness,CXCL13 and CCL19 together induced significant resistance to TNF-α-mediated apoptosis inB-ALL and B-CLL but not CB CD19~+CD34~+ B cells.B-ALL and B-CLL CD19~+CD34~+ B cells expressed elevatedlevel of Paternally Expressed Gene 10 (PEG10),and CXCL13 and CCL19 together significantly up-regulatedPEG10 expression in the cells.We found that CXCL13 and CCL19 together by means of activation of CXCR5and CCR7 up-regulated PEG10 expression and function,subsequent stabilized caspase-3 and caspase-8 inB-ALL and B-CLL CD19~+CD34~+ B cells,and rescued the cells from TNF-α-mediated apoptosis.We suggestedthat normal lymphocytes,especially naive B and T cells,utilized CXCR5/CXCL13 and CCR7/CCL19 formigration,homing,maturation,and cell homeostasis as well as secondary lymphoid tissues organogenesis.Meanwhile certain malignant cells took advantages of CXCR5/CXCL13 and CCR7/CCL19 for infiltration,resistance to apoptosis,and inappropriate proliferation.Cellular & Molecular Immunology.2004;1(4):280-294.     

Distinct and overlapping roles of CXCR5 and CCR7 in B-1 cell homing and early immunity against bacterial pathogens

CXC chemokine receptor (CXCR)5 and CC chemokine receptor (CCR)7 are the major chemokine receptors required for B cell homing and microenvironmental localization during antigen-independent and -dependent B cell differentiation. Here, we show markedly decreased B-1 B cell numbers in the peritoneal cavity of CXCR5-/- and CXCR5-/-CCR7-/- double-deficient mice paralleled by reduced antigen-induced phosphorylcholine-specific immunoglobulin (Ig)M responses after intraperitoneal (i.p.) administration of streptococcal antigen. CCR7-/- mice also revealed a partial reduction in peritoneal B-1 cell numbers combined with a reduced humoral response to i.p. injected bacterial antigen. However, opposite roles of CXCR5 and CCR7 were observed when the frequency of peritoneal B-2 cells was analyzed. CXCR5-/- mice almost completely lacked B-2 cells, whereas CCR7 deficiency engendered an increase in peritoneal B-2 cells. In addition, CCR7-/- mice had enhanced, splenic IgM+ plasma cell responses, whereas the extrafollicular B cell response of the CXCR5-/- mice was not significantly altered compared with wild-type controls. Thus, the two chemokine receptors exert divergent forces at multiple levels of the innate immune response. CXCR5 plays a dominant role in peritoneal B-1 B cell homing and body cavity immunity, but both chemokine receptors are needed for a proportional peritoneal B-2 cell homing and balanced development of an early splenic B cell response.     

Differential expression of chemokine receptors on human IgA+ and IgG+ B cells

Organ-specific lymphocyte homing is dependent on the expression of tissue-specific homing receptors and selected chemokine receptors. During the effector phase of an immune response, IgA and IgG antibody-secreting cells (ASC) are differently distributed in the body. Still, B cell expression of L-selectin and the mucosal homing receptor integrin alpha4beta7 is not related to the isotype produced, but only to the site of antigen encounter. In this study, we examined if differences in chemokine responsiveness between IgA+ and IgG+ B cells could explain their different tissue localization. Circulating CD19+ B cells were isolated and their expression of IgA, IgG, and selected chemokine receptors was determined by flow cytometry. Few Ig+ cells expressed CCR2, CCR3, or CCR9, and there was no difference in the expression of these receptors between IgA+ and IgG+ cells. In contrast, CCR4, CCR5, and CXCR3 was expressed on significantly more IgG+ than IgA+ cells. The function of chemokine receptors on memory B cells and ASC was then tested in the transwell system. IgG+ memory cells migrated to a higher extent than IgA+ cells towards the CXCR3 ligand CXCL11/I-TAC, while there was only a small migration towards the CCR4 ligand CCL17/TARC and the CCR9 ligand CCL25/TECK. ASC migrated poorly to all chemokines tested. In conclusion, this study shows that IgG+ and IgA+ memory B cells have a differential expression of the Th1 associated chemokine receptor CXCR3, as well as of CCR4 and CCR5. In contrast, none of the studied chemokine receptors was preferentially expressed by IgA+ cells.     

The chemokine SDF-1α triggers a chemotactic response and induces cell polarization in human B lymphocytes

We studied the expression and possible functional role of chemokine receptors CXCR3, CXCR4 and CCR5 in normal human B lymphocytes. B cells from both peripheral blood and tonsils expressed high levels of CXCR4 but not the other chemokine receptors tested. CXCR4 ligand, stromal cell-derived factor (SDF)-1α, elicited a potent chemotactic response and induced a polarized motile phenotype in B cells, resulting in redistribution of the adhesion molecule ICAM-3 to a posterior appendage of the cell, termed uropod, and of CXCR4 receptor to the leading edge of migrating B cells. Time-lapse videomicroscopy studies revealed that SDF-1α-treated cells recruited additional bystander B cells through the uropod. SDF-1α induced levels of cellular recruitment comparable to those elicited by polarization-inducing anti-ICAM-3 monoclonal antibody, in an LFA-1/ICAM-1, −3-dependent fashion. Moreover, this chemokine increased intracellular Ca²⁺ levels in B lymphocytes, and induced a rapid CXCR4 receptor down-regulation on the cell surface membrane. These results provide new insight into the important biological role of SDF-1α in physiological processes in which B cells participate, and suggest a key role for chemokines in normal B cell trafficking and recirculation.     

Modulation of chemokine receptor expression and chemotactic responsiveness during differentiation of human naive T cells into Th1 or Th2 cells

Chemokines and their receptors direct movements and encounters of lymphocytes and professional APC into specific microenvironments of lymphoid tissues. Chemokine receptors such as CCR7, CXCR5 and CCR4 that are differentially expressed and modulated in distinct subsets of T cells contribute to establish functionally and spatially segregated microenvironments within secondary lymphoid tissues where T cell activation and differentiation occur. Here, we have explored the modulation of CCR7, CCR4, CCR8 and CXCR5 expression and chemotactic responsiveness to their ligands during commitment of human naive T cells along the Th1 or Th2 differentiation pathway in vitro. Our results document that activation of human naive T cells and differentiation in Th1 or Th2 cells result in progressive down-modulation of CCR7 expression and CCL19 responsiveness. By contrast, expression of CCR4 and responsiveness to CCL22 is rapidly induced at the early stages of both Th1/Th2 cell development. However, while CCR4 expression is further up-regulated upon differentiation into Th2 cells, it is lost on fully differentiated Th1 cells. CCR8 is detected at later time points than CCR4 and exclusively on differentiated Th2 cells as revealed by analysis of mRNA expression and responsiveness to CCL1. Expression of CXCR5 is transiently induced at the early stages of Th cell differentiation, but with distinct kinetics in developing Th1 and Th2 cells. Analysis of human tonsillar CD4(+) T cells reveals a consistent pattern of chemotactic responsiveness and chemokine receptor expression in distinct transitional stages of human T cell activation and differentiation in vivo.     

慢乙肝患者外周血中Th17细胞趋化因子受体的表达水平

目的 检测慢性乙型病毒性肝炎（chronic hepatitis B,CHB）患者外周血中Th17细胞表面趋化因子受体CCR4、CCR6、CXCR3的表达,分析CCR4、CCR6、CXCR3与丙氨酸转氨酶（ALT）、总胆红素（TBil）及HBV DNA载量的相关性.方法 流式细胞仪检测30例CHB患者（CHB组）及15名健康人（对照组）外周血中Th17细胞CCR4、CCR6、CXCR3的表达,与ALT、TBil、HBV DNA载量进行相关性分析.结果 CHB组CD4＋ Th17细胞CCR4、CCR6、CXCR3的表达水平高于对照组,其差异有统计学意义（P＜0.05）.CHB组CD8＋ Th17细胞CCR4、CCR6的表达水平高于对照组,其差异有统计学意义（P＜0.05）.CCR4、CCR6表达水平与ALT、HBV DNA载量呈正相关（P＜0.05）,与TBil水平无相关性（P＞0.05）.结论 CHB患者外周血中Th17细胞表面CCR4、CCR6表达增高,与炎症程度相关,可能涉及Th17细胞引起的肝损伤.     

Chemokine-mediated control of T cell traffic in lymphoid and peripheral tissues

Antigen-driven T cell education and subsequent pathogen elimination present particular challenges for the immune system. Pathogens generally enter the body at peripheral sites such as the skin, gastrointestinal tract or lung, areas from which na?ve T cells are largely excluded. Instead, na?ve T cells constantly recirculate through secondary lymphoid organs, such as lymph nodes and Peyer's patches, in search for antigen brought to these locations by means of afferent lymphatic channels. Here, antigen-loaded dendritic cells present antigen-peptide-MHC complexes to clonotypic T cells and provide appropriate co-stimulatory signals for immune response initiation. As a result, short-lived effector T cells and long-lived memory T cells are generated that reach the peripheral tissue for participation in immune responses and immune surveillance. Effector and memory T cell relocation is non-random, due to tissue-specific "address codes" that allow proper tissue homing. This process involves adhesion molecules, including selectins, integrins, and corresponding vascular ligands as well as the large family of chemokines and their receptors. Here, we discuss the changes in chemokine receptor expression that occur during T cell activation and differentiation, and the ways in which these changes impact on the migration potential of na?ve, effector, and memory T cells. We summarize our current understanding of T cell homing to the T zone and B cell follicles within secondary lymphoid tissues and highlight the two chemokine receptors CCR7 and CXCR5 that recognize chemokines constitutively present either in the T zone (CCR7 ligands CCL19/ELC and CCL21/SLC) or follicular compartment (CXCR5 ligand CXCL13/BCA-1). CCR7 is characteristic for naive and central memory T (T(CM)) cells whereas CXCR5 distinguishes follicular B helper T (T(FH)) cells. In addition, we further subdivide long-lived memory T cells into CCR7-negative effector memory T (T(EM)) cells and peripheral immune surveillance T (T(PS)) cells. The latter term designates the extraordinarily large subset of memory T cells with primary residence in normal (healthy) peripheral tissues. Our current understanding of T(PS) cell migration and function is highly fragmentary, but these cells are thought to provide immediate protection locally at the site of pathogen entry. Here, we propose that the tissue distribution of T(PS) cells is determined by a distinct set of chemokines and corresponding receptors that differs from those operating in secondary lymphoid tissues and inflammatory sites.     

Chemokine receptors are infrequently expressed in malignant and benign mesothelial cells

We studied chemokine receptor expression in malignant mesothelioma (MM), reactive mesothelium (RM), and leukocytes in effusions. The expression of leukocyte markers (CD3, CD4, CD8, CD14, CD16, and CD19) and chemokine receptors (CXCR1, CXCR4, CCR2, CCR5, and CCR7) was studied in 11 MM and 16 RM specimens using flow cytometry. RM specimens showed higher lymphocyte counts (mean rank, 17.6 vs 8.8; P = .004), whereas monocyte numbers were higher in MM (mean rank, 19.5 vs 10.2; P = .002). CXCR1 (P =.006) and CXCR4 (P = .036) expression was higher in MM monocytes. Chemokine receptors were infrequently expressed in MM (0-2/11 effusions per receptor), whereas RM specimens were uniformly negative. Chemokine receptors are widely expressed on leukocytes in MM and RM effusions but are infrequently found on cells of mesothelial origin. This finding suggests a major role for an autocrine chemokine pathway in leukocytes but not in MM cells. The increased monocyte infiltration and their higher chemokine receptor expression in MM effusions may have a tumor-promoting rather than tumor-inhibiting effect.     

Switch in chemokine receptor expression upon TCR stimulation reveals novel homing potential for recently activated T cells.

When naive T lymphocytes are activated and differentiate into memory/effector cells, they down-regulate receptors for constitutive chemokines such as CXCR4 and CCR7 and acquire receptors for inflammatory chemokines such as CCR3, CCR5 and CXCR3, depending on the Th1/Th2 polarization. This switch in chemokine receptor usage leads to the acquisition of the capacity to migrate into inflamed tissues. Using RNase protection assays, staining with specific antibodies, and response to recombinant chemokines, we now show that following TCR stimulation, memory/effector T cells undergo a further and transient switch in receptor expression. CCR1, CCR2, CCR3, CCR5, CCR6 and CXCR3 are down-regulated within 6 h, while CCR7, CCR4, CCR8 and CXCR5 are up-regulated for 2 to 3 days. Up-regulation of CCR7 following TCR stimulation was observed also among resting peripheral blood T cells and required neither co-stimulation nor exogenous IL-2. On the other hand IL-2 down-regulated CXCR5, up-regulated CCR8 and facilitated the recovery of CCR3 and CCR5. Upon TCR stimulation, Th1 and Th2 cells produced comparable sets of chemokines, including RANTES, macrophage inflammatory protein-1beta, I-309, IL-8 and macrophage-derived chemokine, which may modulate surface chemokine receptors and contribute to cell recruitment at sites of antigenic recognition. Altogether these results show that following TCR stimulation effector/memory T cells transiently acquire responsiveness to constitutive chemokines. As a result, T cells that are activated in tissues may either recirculate to draining lymph nodes or migrate to nearby sites of organized ectopic lymphoid tissues.     

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.     

Human intestinal lamina propria and intraepithelial lymphocytes express receptors specific for chemokines induced by inflammation

To determine which chemokine receptors might be involved in T lymphocyte localization to the intestinal mucosa, we examined receptor expression on human intestinal lamina propria lymphocytes (LPL), intraepithelial lymphocytes (IEL) and CD45RO+beta7hi gut homing peripheral blood lymphocytes (PBL). Virtually all LPL and IEL expressed CXCR3 and CCR5, receptors that have been associated with Th1(Tc1)/Th0 lymphocytes, while CCR3 and CCR4, receptors associated with Th2 (Tc2)lymphocytes, CCR7, CXCR1 and CXCR2 were not expressed. CXCR3 and CCR5 receptors were functional, as LPL and IEL migrated to their respective ligands I-TAC and RANTES. In addition, most alphaEbeta7- LPL and IEL expressed high levels of CCR2. While the majority of CD45RO(-)beta7hi PBL also expressed CXCR3 and CCR5, a proportion of these cells were CXCR3- and/or CCR5- and some expressed CCR4 and/or CCR7, indicating that lymphocytes recruited to the intestinal mucosa represent a subset of these cells. In summary, our results show that LPL and IEL within the normal intestine express a specific and similar array of chemokine receptors whose ligands are constitutively expressed in the intestinal mucosa and whose expression is up-regulated during intestinal inflammation. These results support the view that CXCR3, CCR5 and CCR2 may play an important role in lymphocyte localization within the intestinal mucosa.     

CXCR4 expression enhances diffuse large B cell lymphoma dissemination and decreases patient survival

The chemokine receptor CXCR4 has been implicated in the migration and trafficking of malignant B cells in several haematological malignancies. Over‐expression of CXCR4 has been identified in haematological tumours, but data concerning the role of this receptor in diffuse large B cell lymphoma (DLBCL) are lacking. CXCR4 is a marker of poor prognosis in various neoplasms, correlating with metastatic disease and decreased survival of patients. We studied CXCR4 involvement in cell migration in vitro and dissemination in vivo. We also evaluated the prognostic significance of CXCR4 in 94 biopsies of DLBCL patients. We observed that the level of expression of CXCR4 in DLBCL cell lines correlated positively with in vitro migration. Expression of the receptor was also associated with increased engraftment and dissemination, and decreased survival time in NOD/SCID mice. Furthermore, administration of a specific CXCR4 antagonist, AMD3100, decreased dissemination of DLBCL cells in a xenograft mouse model. In addition, we found that CXCR4 expression is an independent prognostic factor for shorter overall survival and progression‐free survival in DLBCL patients. These results show that CXCR4 mediates dissemination of DLBCL cells and define for the first time its value as an independent prognostic marker in DLBCL patients. Copyright © 2014 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd     

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.     

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.