CC chemokine receptor (CCR)3/eotaxin is followed by CCR4/monocyte-derived chemokine in mediating pulmonary T helper lymphocyte type 2 recruitment after serial antigen challenge in vivo

Isolated peripheral blood CD4 cells from allergic individuals express CC chemokine receptor (CCR)3 and CCR4 after expansion in vitro. In addition, human T helper type 2 (Th2) cells polarized in vitro selectively express CCR3 and CCR4 at certain stages of activation/differentiation and respond preferentially to the ligands eotaxin and monocyte-derived chemokine (MDC). However, controversy arises when the in vivo significance of this distinct expression is discussed. To address the functional role of CCR3/eotaxin and CCR4/MDC during the in vivo recruitment of Th2 cells, we have transferred effector Th cells into naive mice to induce allergic airway disease. Tracking of these cells after repeated antigen challenge has established that both CCR3/eotaxin and CCR4/MDC axes contribute to the recruitment of Th2 cells to the lung, demonstrating the in vivo relevance of the expression of these receptors on Th2 cells. We have shown that involvement of the CCR3/eotaxin pathway is confined to early stages of the response in vivo, whereas repeated antigen stimulation results in the predominant use of the CCR4/MDC pathway. We propose that effector Th2 cells respond to both CCR3/eotaxin and CCR4/MDC pathways initially, but that a progressive increase in CCR4-positive cells results in the predominance of the CCR4/MDC axis in the long-term recruitment of Th2 cells in vivo.     

Resistance to experimental autoimmune encephalomyelitis in mice lacking the CC chemokine receptor (CCR)2

Monocyte recruitment to the central nervous system (CNS) is a necessary step in the development of pathologic inflammatory lesions in experimental autoimmune encephalomyelitis (EAE), a murine model of multiple sclerosis. Monocyte chemoattractant protein (MCP)-1, a potent agonist for directed monocyte migration, has been implicated in the pathogenesis of EAE. Here we report that deficiency in CC chemokine receptor (CCR)2, the receptor for MCP-1, confers resistance to EAE induced with a peptide derived from myelin oligodendrocyte glycoprotein peptide 35-55 (MOGp35-55). CCR2(-/)- mice immunized with MOGp35-55 failed to develop mononuclear cell inflammatory infiltrates in the CNS and failed to increase CNS levels of the chemokines RANTES (regulated on activation, normal T cell expressed and secreted), MCP-1, and interferon (IFN)-inducible protein 10 (IP-10) as well the chemokine receptors CCR1, CCR2, and CCR5. Additionally, T cells from CCR2(-/)- immunized mice showed decreased antigen-induced proliferation and production of IFN-gamma compared with wild-type immunized controls, suggesting that CCR2 enhances the T helper cell type 1 immune response in EAE. These data indicate that CCR2 plays a necessary and nonredundant role in the pathogenesis of EAE.     

Natural proteolytic processing of hemofiltrate CC chemokine 1 generates a potent CC chemokine receptor (CCR)1 and CCR5 agonist with anti-HIV properties

Hemofiltrate CC chemokine (HCC)-1 is a recently described human chemokine that is constitutively expressed in numerous tissues and is present at high concentrations in normal plasma. Using a cell line expressing CC chemokine receptor (CCR)5 as a bioassay, we isolated from human hemofiltrate an HCC-1 variant lacking the first eight amino acids. HCC-1[9-74] was a potent agonist of CCR1, CCR3, and CCR5 and promoted calcium flux and chemotaxis of T lymphoblasts, monocytes, and eosinophils. It also blocked entry of HIV-1 strains using CCR5 as coreceptor. Limited tryptic digestion of HCC-1 generated the active variant. Conditioned media from several tumor cell lines activated HCC-1 with a high efficiency, and this activity could be inhibited by serine protease inhibitors. Our results indicate that HCC-1 represents a nonfunctional precursor that can be rapidly converted to the active chemokine by proteolytic processing. This process represents an additional mechanism by which tumor cells might generate chemoattractant molecules and recruit inflammatory cells. It might also affect HIV-1 replication in infected individuals and play an important role in AIDS pathogenesis.     

The Kaposi's sarcoma-related herpesvirus (KSHV)-encoded chemokine vMIP-I is a specific agonist for the CC chemokine receptor (CCR)8.

The Kaposi's sarcoma-related herpesvirus (KSHV), also designated human herpesvirus 8, is the presumed etiologic agent of Kaposi's sarcoma and certain lymphomas. Although KSHV encodes several chemokine homologues (viral macrophage inflammatory protein [vMIP]-I, -II, and -III), only vMIP-II has been functionally characterized. We report here that vMIP-I is a specific agonist for the CC chemokine receptor (CCR)8 that is preferentially expressed on Th2 T cells. Y3 cells transfected with CCR8 produced a calcium flux in response to vMIP-I and responded vigorously in in vitro chemotaxis assays. In competition binding experiments, the interaction of vMIP-I with CCR8 was shown to be specific and of high affinity. In contrast to its agonist activity at CCR8, vMIP-I did not interact with CCR5 or any of 11 other receptors examined. Furthermore, vMIP-I was unable to inhibit CCR5-mediated HIV infection. These findings suggest that expression of vMIP-I by KSHV may influence the Th1/Th2 balance of the host immune response.     

A highly selective CC chemokine receptor (CCR)8 antagonist encoded by the poxvirus molluscum contagiosum

The MC148 CC chemokine from the human poxvirus molluscum contagiosum (MCV) was probed in parallel with viral macrophage inflammatory protein (vMIP)-II encoded by human herpesvirus 8 (HHV8) in 16 classified human chemokine receptors. In competition binding using radiolabeled endogenous chemokines as well as radiolabeled MC148, MC148 bound with high affinity only to CCR8. In calcium mobilization assays, MC148 had no effect on its own on any of the chemokine receptors, but in a dose-dependent manner blocked the stimulatory effect of the endogenous I-309 chemokine on CCR8 without affecting chemokine-induced signaling of any other receptor. In contrast, vMIP-II acted as an antagonist on 10 of the 16 chemokine receptors, covering all four classes: XCR, CCR, CXCR, and CX(3)CR. In chemotaxis assays, MC148 specifically blocked the I-309-induced response but, for example, not stromal cell-derived factor 1alpha, monocyte chemoattractant protein 1, or interleukin 8-induced chemotaxis. We thus concluded that the two viruses choose two different ways to block the chemokine system: HHV8 encodes the broad-spectrum chemokine antagonist vMIP-II, whereas MCV encodes a highly selective CCR8 antagonist, MC148, conceivably to interfere with monocyte invasion and dendritic cell function. Because of its pharmacological selectivity, the MC148 protein could be a useful tool in the delineation of the role played by CCR8 and its endogenous ligand, I-309.     

Blockade of CC chemokine receptor 5 (CCR5)-tropic human immunodeficiency virus-1 replication in human lymphoid tissue by CC chemokines.

The CC chemokines MIP-1alpha, MIP-1beta, and RANTES suppress replication of certain HIV-1 strains in cultured PBMC and T cell lines by blocking interaction of gp120 with CC chemokine receptor 5 (CCR5). However, the same chemokines can enhance HIV-1 replication in cultured macrophages. The net effect of chemokines on HIV-1 infection in intact lymphoid tissue, the major reservoir of HIV-1 in vivo, is unknown and unpredictable since the tissue contains both T lymphocytes and macrophages. Here we show that exogenous MIP-1alpha, MIP-1beta, and RANTES markedly suppressed replication of CCR5-tropic HIV-1 strains in blocks of human lymphoid tissue infected ex vivo. Moreover, endogenous MIP-1alpha, MIP-1beta, and RANTES were upregulated in tissues infected ex vivo with CXC chemokine receptor 4-tropic but not CCR5-tropic HIV-1. Such an upregulation may contribute to the virus phenotype shift in the course of HIV disease in vivo.     

Th2型趋化因子受体CCR4在原位肝移植急性排斥反应中的表达

目的　通过检测Th2型趋化因子受体CCR4在移植肝脏急性排斥反应中的表达,探讨Th2型细胞在肝移植急性排斥反应中的作用机制。方法　根据Banff病理分级将原位肝移植术后肝穿刺活检标本分成4组,应用RT -PCR方法半定量分析各组标本中CCR4的mRNA水平。结果　轻度排斥组中11例CCR4高水平表达;中度排斥组中6例、未排斥组中5例CCR4中度水平表达;正常对照组、重度排斥组CCR4均轻度表达。结论　肝移植免疫微环境中CCR4的表达可能与免疫耐受的诱导有关;Th1/Th2细胞的极化是影响免疫耐受诱导的关键因素。     

Interleukin-2 regulates CC chemokine receptor expression and chemotactic responsiveness in T lymphocytes

Several studies have shown that CC chemokines attract T lymphocytes, and that CD45RO+, memory phenotype cells are considered to be the main responders. The results, however, have often been contradictory and the role of lymphocyte activation and proliferation has remained unclear. Using CD45RO+ blood lymphocytes cultured under different stimulatory conditions, we have now studied chemotaxis as well as chemokine receptor expression. Expression of the RANTES/MIP-1 alpha receptor (CC- CKR1) and the MCP-1 receptor (CC-CKR2) was highly correlated with migration toward RANTES, MCP-1, and other CC chemokines, and was strictly dependent on the presence of IL-2 in the culture medium. Migration and receptor expression were rapidly downregulated when IL-2 was withdrawn, but were fully restored when IL-2 was added again. The effect of IL-2 could be partially mimicked by IL-4, IL-10, or IL-12, but not by IL-13, IFN gamma, IL-1 beta, TNF-alpha, or by exposure to anti-CD3, anti-CD28 or phytohemagglutinin. Activation of fully responsive lymphocytes through the TCR/CD3 complex and CD28 antigen actually had the opposite effect. It rapidly downregulated receptor expression and consequent migration even in the presence of IL-2. In contrast to the effects on CC chemokine receptors, stimulation of CD45RO+ T lymphocytes with IL-2 neither induced the expression of the CXC chemokine receptors, IL8-R1 and IL8-R2, nor chemotaxis to IL-8. The prominent role of IL-2 in CC chemokine responsiveness of lymphocytes suggests that IL-2-mediated expansion is a prerequisite for the recruitment of antigen-activated T cells into sites of immune and inflammatory reactions.     

CC chemokine receptor 7-dependent and -independent pathways for lymphocyte homing: modulation by FTY720.

Cognate interaction of chemokine receptor CCR7 on lymphocytes with its ligands CCL19 and CCL21 expressed on high endothelial venules (HEVs) is essential for effective migration of T and B cells across HEVs into secondary lymphoid organs. Plt mice, which lack expression of CCL19 and CCL21-ser, both ligands for CCR7 on HEVs, as well as CCR7-deficient mice, have a defective cell migration and reduced homing of lymphocytes. FTY720, a novel immunosuppressant, causes a reduction of lymphocytes in peripheral blood and tissues and their sequestration into lymphoid tissues. In this study we demonstrate that FTY720 rescues the homing defect in both CCR7(-/-) mice and plt mice. After FTY720 treatment, the number of CD4(+) and CD8(+) T cells as well as B cells in peripheral blood is reduced while pertussis toxin-sensitive homing into peripheral lymph nodes, mesenteric lymph node, and Peyer's patches is increased. Immunohistology demonstrates that FTY720 enables these cells to enter lymphoid tissue through HEVs. Thus, our data suggest an alternative G-alpha(i)-dependent, CCR7-CCL19/CCL21-independent mechanism for lymphocyte homing through HEVs which is strongly augmented in the presence of FTY720.     

Lung dendritic cells imprint T cell lung homing and promote lung immunity through the chemokine receptor CCR4

T cell trafficking into the lung is critical for lung immunity, but the mechanisms that mediate T cell lung homing are not well understood. Here, we show that lung dendritic cells (DCs) imprint T cell lung homing, as lung DC–activated T cells traffic more efficiently into the lung in response to inhaled antigen and at homeostasis compared with T cells activated by DCs from other tissues. Consequently, lung DC–imprinted T cells protect against influenza more effectively than do gut and skin DC–imprinted T cells. Lung DCs imprint the expression of CCR4 on T cells, and CCR4 contributes to T cell lung imprinting. Lung DC–activated, CCR4-deficient T cells fail to traffic into the lung as efficiently and to protect against influenza as effectively as lung DC–activated, CCR4-sufficient T cells. Thus, lung DCs imprint T cell lung homing and promote lung immunity in part through CCR4.CD4⁺ T cells orchestrate the recruitment and subsequent activation of innate and adaptive immune cells in the tissue through the production of cytokines and critically contribute to the generation of a robust immune response to invading pathogens (Reinhardt et al., 2006). A prerequisite for CD4⁺ T cell participation in host defense is their recruitment into peripheral nonlymphoid tissue both in response to pathogens and at homeostasis so that antigen-experienced T cells are positioned where pathogen reencounter is most likely to occur. The mechanisms that govern this strategic distribution of T cells into tissues are not fully defined.Organs with large epithelial surfaces such as the gut and the skin are in constant contact with the environment and are exposed to potential pathogens on a regular basis and therefore need an efficient immune response strategy to prevent infections at these sites. The unique structure and function of each organ determine its exposures and vulnerabilities to specific pathogens and make reexposure to a particular pathogen more likely in the same organ. For example, by virtue of its ecology, the gut is susceptible to infection with Salmonella and Shigella, organisms which are not pathogens in the skin. To streamline T cell memory immune responses based on the predictability of pathogen reexposure, the gut and the skin have evolved tissue-selective T cell imprinting, a process whereby DCs derived from the gut instruct T cells to home preferentially into the gut, whereas DCs derived from the skin instruct T cells to preferentially home into the skin. Gut DCs imprint the expression of α4β7 and CCR9 on T cells, and in doing so enable their entry into the small intestine in response to intestinal MAdCAM-1 and CCL25, respectively (Stagg et al., 2002; Johansson-Lindbom et al., 2003; Mora et al., 2003). Similarly, skin-derived DCs imprint T cell expression of P- and E-selectin ligands and CCR10, allowing T cell skin homing via cutaneous P- and E-selectins and CCL27, respectively (Campbell and Butcher, 2002; Dudda et al., 2004; Sigmundsdottir et al., 2007). This may explain why peripheral blood memory T cells that proliferate in response to rotavirus, a gut pathogen, are α4β7⁺ (Rott et al., 1997), whereas peripheral blood T cells specific for herpes simplex virus 2, a skin tropic virus, express high levels of CLA (Koelle et al., 2002). The unique structure and function of each organ also offer a distinct set of tissue-specific autoantigens, such that the autoantigens generated in the intestine would be different from those generated in the skin. Therefore, tissue-selective T cell imprinting might have also evolved to enable tissue-specific regulatory T cells to home efficiently to the location of their autoantigens.Tissue-selective T cell imprinting was described a decade ago for the gut and the skin and to date has not been shown for any other organ, raising the possibility that it might be a phenomenon restricted to these two organs. Like the gut and the skin, however, the lung is a large epithelial organ in continuous contact with the environment and potential pathogens. The lung also has its own unique structure and function, specific pathogen susceptibility (i.e., pneumococcus and influenza), and autoantigens and thus is poised to benefit from tissue-selective T cell imprinting. Understanding whether lung DCs imprint T cell lung homing is fundamental to understanding T cell immunity to inhaled antigens and pathogens. Whether lung DCs instruct T cells to home to the lung has implications for vaccine development and potentially opens novel therapeutic approaches for a variety of inflammatory T cell–mediated lung diseases. Here, we sought to determine whether lung DCs imprint T cell lung homing and, if so, the impact of lung imprinting on lung immunity.     

Recruitment of Foxp3+ T regulatory cells mediating allograft tolerance depends on the CCR4 chemokine receptor

Although certain chemokines and their receptors guide homeostatic recirculation of T cells and others promote recruitment of activated T cells to inflammatory sites, little is known of the mechanisms underlying a third function, migration of Foxp3(+) regulatory T (T reg) cells to sites where they maintain unresponsiveness. We studied how T reg cells are recruited to cardiac allografts in recipients tolerized with CD154 monoclonal antibody (mAb) plus donor-specific transfusion (DST). Real-time polymerase chain reaction showed that intragraft Foxp3 levels in tolerized recipients were approximately 100-fold higher than rejecting allografts or allografts associated with other therapies inducing prolonged survival but not tolerance. Foxp3(+) cells were essential for tolerance because pretransplant thymectomy or peritransplant depletion of CD25(+) cells prevented long-term survival, as did CD25 mAb therapy in well-functioning allografts after CD154/DST therapy. Analysis of multiple chemokine pathways showed that tolerance was accompanied by intragraft up-regulation of CCR4 and one of its ligands, macrophage-derived chemokine (CCL22), and that tolerance induction could not be achieved in CCR4(-/-) recipients. We conclude that Foxp3 expression is specifically up-regulated within allografts of mice displaying donor-specific tolerance, that recruitment of Foxp3-expressing T reg cells to an allograft tissue is dependent on the chemokine receptor, CCR4, and that, in the absence of such recruitment, tolerizing strategies such as CD154 mAb therapy are ineffectual.     

Differential requirements for the chemokine receptor CCR7 in T cell activation during Listeria monocytogenes infection

Effective priming of T cell responses depends on cognate interactions between naive T cells and professional antigen-presenting cells (APCs). This contact is the result of highly coordinated migration processes, in which the chemokine receptor CCR7 and its ligands, CCL19 and CCL21, play a central role. We used the murine Listeria monocytogenes infection model to characterize the role of the CCR7/CCR7 ligand system in the generation of T cell responses during bacterial infection. We demonstrate that efficient priming of naive major histocompatibility complex (MHC) class Ia-restricted CD8+ T cells requires CCR7. In contrast, MHC class Ib-restricted CD8+ T cells and MHC class II-restricted CD4+ T cells seem to be less dependent on CCR7; memory T cell responses are independent of CCR7. Infection experiments with bone marrow chimeras or mice reconstituted with purified T cell populations indicate that CCR7 has to be expressed on CD8+ T cells and professional APCs to promote efficient MHC class Ia-restricted T cell priming. Thus, different T cell subtypes and maturation stages have discrete requirements for CCR7.     

趋化因子受体CCR4、CCR5在系统性红斑狼疮患者外周血CD4＋T淋巴细胞上的表达及其意义

目的探讨系统性红斑狼疮（SLE）患者趋化因子受体CCR4和CCR5在外周血淋巴细胞表面的表达及其意义。方法流式细胞仪计数法对113例SLE患者和50例健康体检者外周血淋巴细胞表面CCR4和CCR5的表达情况进行检测,分析及评价SLE患者外周血淋巴细胞中CCR4＋和CCR5＋T淋巴细胞的百分数。结果非狼疮性肾炎（nLN）SLE组外周血CCR4＋CD4＋T%明显高于健康对照组（P〈0.01）;狼疮性肾炎SLE组外周血CCR4＋CD4＋T%明显高于健康对照组（P〈0.001）;LNSLE组外周血CCR4＋CD4＋T%明显高于nLNSLE组（P〈0.01）;nLNSLE组外周血CCR5＋CD4＋T%高于健康对照组（P〈0.05）;LNSLE组外周血CCR5＋CD4＋T%明显高于健康对照组（P〈0.001）;LNSLE组外周血CCR5＋CD4＋T%明显高于nLNSLE组（P〈0.01）。SLE活动组血清CCR4＋CD4＋T%与CCR5＋CD4＋T%较非活动组和对照组明显升高（P〈0.01）;活动性狼疮性肾炎（LN）与活动性无肾损伤组及对照组比较,其差异具有显著统计学意义（P〈0.01）。nLNSLE组外周血CCR4＋CD4＋T%与CCR5＋CD4＋T%有相关性（r=0.619,P〈0.05）;LNSLE组外周血CCR4＋CD4＋T%与CCR5＋CD4＋T%有明显相关性（r=0.68,P〈0.01）;血清CCR4＋CD4＋T%水平随着SLE疾病活动水平明显升高,与总的系统性红斑狼疮疾病活动性指数（SLEDAI）评分密切相关（r=0.6382,P〈0.001）;与SLEDAI肾评分亦密切相关（r=0.6980,P〈0.001）;而CCR5＋CD4＋T%与疾病活动度不相关（r=0.16,P〉0.05）。结论以上结果表明CCR4和CCR5在T细胞趋化至病变部位的过程中可能发挥重要作用,CCR4＋CD4＋T%与CCR5＋CD4＋T%可能在肾损伤中起着十分重要的作用,血清CCR4＋CD4＋T%、CCR5＋CD4＋T%与SLE疾病活动密切相关,可作为SLE疾病活动,尤其是监测狼疮性肾损伤的重要指标。     

CXC chemokine receptor 1 (CXCR1) is expressed mainly by neutrophils in inflamed gut and stomach tissues

CXC chemokine receptor 1 (CXCR1) is one of the important receptors for CXC chemokines with ELR motif, of which interleukin 8 (IL-8; CXCL8) is representative. To identify the cell type(s) of CXCR1-expressing cells in inflamed stomach and gut tissues, we performed immunoperoxidase method using pre-fixed frozen sections. In chronic gastritis associated with Helicobacter pylori infection (7 cases), CXCR1 was positive in neutrophils (polymorphonuclear leucocytes) in the lamina propria near the neck region and those in pit abscess. In ulcerative colitis (6 cases) and Crohn's disease (5 cases), CXCR1 was sporadically expressed by neutrophils in the mucosa, and particularly CXCR1+ neutrophils were abundantly distributed in inflammatory granulation tissue in ulcer base. Double staining confirmed co-localization of CXCR1 and neutrophil elastase. Neither CD3+ T lymphocytes nor CD68+ macrophages were positive for CXCR1. Immunoelectron microscopy confirmed the cell surface localization of CXCR1. Neutrophils protect the host from microbial pathogens. However, they also cause damages to host tissues in chronic inflammation. Therefore, our study underscores the importance of CXCR1 expression in inflammatory processes.     

The CC chemokine thymus-derived chemotactic agent 4 (TCA-4, secondary lymphoid tissue chemokine, 6Ckine, exodus-2) triggers lymphocyte function-associated antigen 1-mediated arrest of rolling T lymphocytes in peripheral lymph node high endothelial venules

T cell homing to peripheral lymph nodes (PLNs) is defined by a multistep sequence of interactions between lymphocytes and endothelial cells in high endothelial venules (HEVs). After initial tethering and rolling via L-selectin, firm adhesion of T cells requires rapid upregulation of lymphocyte function-associated antigen 1 (LFA-1) adhesiveness by a previously unknown pathway that activates a Galpha(i)-linked receptor. Here, we used intravital microscopy of murine PLNs to study the role of thymus-derived chemotactic agent (TCA)-4 (secondary lymphoid tissue chemokine, 6Ckine, Exodus-2) in homing of adoptively transferred T cells from T-GFP mice, a transgenic strain that expresses green fluorescent protein (GFP) selectively in naive T lymphocytes (T(GFP) cells). TCA-4 was constitutively presented on the luminal surface of HEVs, where it was required for LFA-1 activation on rolling T(GFP) cells. Desensitization of the TCA-4 receptor, CC chemokine receptor 7 (CCR7), blocked T(GFP) cell adherence in wild-type HEVs, whereas desensitization to stromal cell-derived factor (SDF)-1alpha (the ligand for CXC chemokine receptor 4 [CXCR4]) did not affect T(GFP) cell behavior. TCA-4 protein was not detected on the luminal surface of PLN HEVs in plt/plt mice, which have a congenital defect in T cell homing to PLNs. Accordingly, T(GFP) cells rolled but did not arrest in plt/plt HEVs. When TCA-4 was injected intracutaneously into plt/plt mice, the chemokine entered afferent lymph vessels and accumulated in draining PLNs. 2 h after intracutaneous injection, luminal presentation of TCA-4 was detectable in a subset of HEVs, and LFA-1-mediated T(GFP) cell adhesion was restored in these vessels. We conclude that TCA-4 is both required and sufficient for LFA-1 activation on rolling T cells in PLN HEVs. This study also highlights a hitherto undocumented role for chemokines contained in afferent lymph, which may modulate leukocyte recruitment in draining PLNs.     

CC chemokine receptor (CCR)2 is required for langerhans cell migration and localization of T helper cell type 1 (Th1)-inducing dendritic cells. Absence of CCR2 shifts the Leishmania major-resistant phenotype to a susceptible state dominated by Th2 cytokines, b cell outgrowth, and sustained neutrophilic inflammation

There is growing evidence that chemokines and their receptors regulate the movement and interaction of antigen-presenting cells such as dendritic cells (DCs) and T cells. We tested the hypothesis that the CC chemokine receptor (CCR)2 and CCR5 and the chemokine macrophage inflammatory protein (MIP)-1alpha, a ligand for CCR5, influence DC migration and localization. We found that deficiency of CCR2 but not CCR5 or MIP-1alpha led to distinct defects in DC biology. Langerhans cell (skin DC) density in CCR2-null mice was normal, and their ability to migrate into the dermis was intact; however, their migration to the draining lymph nodes was markedly impaired. CCR2-null mice had lower numbers of DCs in the spleen, and this was primarily due to a reduction in the CD8alpha(1) T helper cell type 1 (Th1)-inducing subset of DCs. Additionally, there was a block in the Leishmania major infection-induced relocalization of splenic DCs from the marginal zone to the T cell areas. We propose that these DC defects, in conjunction with increased expression of B lymphocyte chemoattractant, a B cell-specific chemokine, may collectively contribute to the striking B cell outgrowth and Th2 cytokine-biased nonhealing phenotype that we observed in CCR2-deficient mice infected with L. major. This disease phenotype in mice with an L. major-resistant genetic background but lacking CCR2 is strikingly reminiscent of that observed typically in mice with an L. major-susceptible genetic background. Thus, CCR2 is an important determinant of not only DC migration and localization but also the development of protective cell-mediated immune responses to L. major.     

Chemokine receptor CCR5 promotes leukocyte trafficking to the brain and survival in West Nile virus infection

The molecular immunopathogenesis of West Nile virus (WNV) infection is poorly understood. Here, we characterize a mouse model for WNV using a subcutaneous route of infection and delineate leukocyte subsets and immunoregulatory factors present in the brains of infected mice. Central nervous system (CNS) expression of the chemokine receptor CCR5 and its ligand CCL5 was prominently up-regulated by WNV, and this was associated with CNS infiltration of CD4+ and CD8+ T cells, NK1.1+ cells and macrophages expressing the receptor. The significance of CCR5 in pathogenesis was established by mortality studies in which infection of CCR5-/- mice was rapidly and uniformly fatal. In the brain, WNV-infected CCR5-/- mice had increased viral burden but markedly reduced NK1.1+ cells, macrophages, and CD4+ and CD8+ T cells compared with WNV-infected CCR5+/+ mice. Adoptive transfer of splenocytes from WNV-infected CCR5+/+ mice into infected CCR5-/- mice increased leukocyte accumulation in the CNS compared with transfer of splenocytes from infected CCR5-/- mice into infected CCR5-/- mice, and increased survival to 60%, the same as in infected CCR5+/+ control mice. We conclude that CCR5 is a critical antiviral and survival determinant in WNV infection of mice that acts by regulating trafficking of leukocytes to the infected brain.     

Aberrant in vivo T helper type 2 cell response and impaired eosinophil recruitment in CC chemokine receptor 8 knockout mice

Chemokine receptors transduce signals important for the function and trafficking of leukocytes. Recently, it has been shown that CC chemokine receptor (CCR)8 is selectively expressed by Th2 subsets, but its functional relevance is unclear. To address the biological role of CCR8, we generated CCR8 deficient (-/-) mice. Here we report defective T helper type 2 (Th2) immune responses in vivo in CCR8(-/)- mice in models of Schistosoma mansoni soluble egg antigen (SEA)-induced granuloma formation as well as ovalbumin (OVA)- and cockroach antigen (CRA)-induced allergic airway inflammation. In these mice, the response to SEA, OVA, and CRA showed impaired Th2 cytokine production that was associated with aberrant type 2 inflammation displaying a 50 to 80% reduction in eosinophils. In contrast, a prototypical Th1 immune response, elicited by Mycobacteria bovis purified protein derivative (PPD) was unaffected by CCR8 deficiency. Mechanistic analyses indicated that Th2 cells developed normally and that the reduction in eosinophil recruitment was likely due to systemic reduction in interleukin 5. These results indicate an important role for CCR8 in Th2 functional responses in vivo.     

Dissection of the B10.D2 anti-H-2Kb cytolytic T lymphocyte receptor repertoire

The B10.D2 cytolytic T lymphocyte (CTL) receptor repertoire specific for the H-2Kb alloantigen has been studied by determining the reactivity patterns of monoclonal CTL against a panel of seven different H-2Kb mutants. The repertoire is extremely diverse and contains a minimum of approximately 50 different specificities against unique antigenic determinants on the H-2Kb molecule. Each specificity appears at a maximum frequency of 1 in 18,000 CTL precursors. These studies have also served to dissect the antigenic composition of the H-2Kb molecule. Very few CTL clonotypes share recognition of all the mutants, thereby indicating the lack of conservation of a b-type antigenic region. In addition, the degree to which each mutant shares antigenic determinants with the standard H-2Kb molecule has been determined.     

In vivo-activated CD4 T cells upregulate CXC chemokine receptor 5 and reprogram their response to lymphoid chemokines.

Migration of antigen-activated CD4 T cells to B cell areas of lymphoid tissues is important for mounting T cell-dependent antibody responses. Here we show that CXC chemokine receptor (CXCR)5, the receptor for B lymphocyte chemoattractant (BLC), is upregulated on antigen-specific CD4 T cells in vivo when animals are immunized under conditions that promote T cell migration to follicles. In situ hybridization of secondary follicles for BLC showed high expression in mantle zones and low expression in germinal centers. When tested directly ex vivo, CXCR5(hi) T cells exhibited a vigorous chemotactic response to BLC. At the same time, the CXCR5(hi) cells showed reduced responsiveness to the T zone chemokines, Epstein-Barr virus-induced molecule 1 (EBI-1) ligand chemokine (ELC) and secondary lymphoid tissue chemokine (SLC). After adoptive transfer, CXCR5(hi) CD4 T cells did not migrate to follicles, indicating that additional changes may occur after immunization that help direct T cells to follicles. To further explore whether T cells could acquire an intrinsic ability to migrate to follicles, CD4(-)CD8(-) double negative (DN) T cells from MRL-lpr mice were studied. These T cells normally accumulate within follicles of MRL-lpr mice. Upon transfer to wild-type recipients, DN T cells migrated to follicle proximal regions in all secondary lymphoid tissues. Taken together, our findings indicate that reprogramming of responsiveness to constitutively expressed lymphoid tissue chemokines plays an important role in T cell migration to the B cell compartment of lymphoid tissues.