CCL25 mediates the localization of recently activated CD8alphabeta(+) lymphocytes to the small-intestinal mucosa

The recruitment of antigen-specific T lymphocytes to the intestinal mucosa is central to the development of an effective mucosal immune response, yet the mechanism by which this process occurs remains to be fully defined. Here we show that the CC chemokine receptor 9 (CCR9) is selectively and functionally expressed on murine alpha(E)beta(7)(+) naive CD8alphabeta(+) lymphocytes and a subset of recently activated CD69(+) CD8alphabeta(+) lymphocytes. Using a T cell receptor transgenic transfer model, we demonstrate that CCR9 expression is functionally maintained on CD8alphabeta(+) lymphocytes following activation in mesenteric lymph nodes but rapidly downregulated on CD8alphabeta(+) lymphocytes activated in peripheral lymph nodes. These recently activated CCR9(+) CD8alphabeta(+) lymphocytes selectively localized to the small-intestinal mucosa, and in vivo neutralization of the CCR9 ligand, CCL25, reduced the ability of these cells to populate the small-intestinal epithelium. Together these results demonstrate an important role for chemokines in the localization of T lymphocytes to the small-intestinal mucosa and suggest that targeting CCL25 and/or CCR9 may provide a means to selectively modulate small-intestinal immune responses.     

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.     

CCR7 ligands stimulate the intranodal motility of T lymphocytes in vivo

In contrast to lymphocyte homing, little is known about molecular cues controlling the motility of lymphocytes within lymphoid organs. Applying intravital two-photon microscopy, we demonstrate that chemokine receptor CCR7 signaling enhances the intranodal motility of CD4(+) T cells. Compared to wild-type (WT) cells, the average velocity and mean motility coefficient of adoptively transferred CCR7-deficient CD4(+) T lymphocytes in T cell areas of WT recipients were reduced by 33 and 55%, respectively. Both parameters were comparably reduced for WT T lymphocytes migrating in T cell areas of plt/plt mice lacking CCR7 ligands. Importantly, systemic application of the CCR7 ligand CCL21 was sufficient to rescue the motility of WT T lymphocytes inside T cell areas of plt/plt recipients. Comparing the movement behavior of T cells in subcapsular areas that are devoid of detectable amounts of CCR7 ligands even in WT mice, we failed to reveal any differences between WT and plt/plt recipients. Furthermore, in both WT and plt/plt recipients, highly motile T cells rapidly accumulated in the subcapsular region after subcutaneous injection of the CCR7 ligand CCL19. Collectively, these data identify CCR7 and its ligands as important chemokinetic factors stimulating the basal motility of CD4(+) T cells inside lymph nodes in vivo.     

A role for CCR4 in development of mature circulating cutaneous T helper memory cell populations

Expression of the chemokine receptor CCR4 is strongly associated with trafficking of specialized cutaneous memory T helper (Th) lymphocytes to the skin. However, it is unknown whether CCR4 itself participates in the development of cutaneous Th populations. We have addressed this issue via competitive bone marrow (BM) reconstitution assays; equal numbers of BM cells from CCR4(+/+) and CCR4(-/-) donors were allowed to develop side-by-side within RAG-1(-/-) hosts. Cells from both donor types developed equally well into B cells, naive CD8 T cells, naive CD4 T cells, interferon-gamma(+) Th1 cells, and interleukin-4(+) Th2 cells. In marked contrast, circulating cutaneous memory Th cells (i.e., E-selectin ligand(+) [E-lig(+)]) were more than fourfold more likely to be derived from CCR4(+/+) donors than from CCR4(-/-) donors. Most of this effect resides within the CD103(+) subset of the E-lig(+) Th population, in which donor CCR4(+/+) cells can outnumber CCR4(-/-) cells by >12-fold. No similar effect was observed for alpha4beta7(+) intestinal memory Th cells or CD103(+)/E-lig(-) Th cells. We conclude that CCR4 expression provides a competitive advantage to cutaneous Th cells, either by participating in their development from naive Th cells, or by preferentially maintaining them within the memory population over time.     

Phenotype,localization, and mechanism of suppression of CD4(+)CD25(+) human thymocytes

Phenotypic markers, localization, functional activities, and mechanisms of action in vitro of CD4(+)CD25(+) T cells, purified from postnatal human thymuses, were investigated. These cells showed poor or no proliferation in mixed lymphocyte culture (MLC), and suppressed in a dose-dependent fashion the proliferative response to allogeneic stimulation of CD4(+)CD25(-) thymocytes. Virtually all CD4(+)CD25(+) thymocytes constitutively expressed cytoplasmic T lymphocyte antigen (CTLA)-4, surface tumor necrosis factor type 2 receptor (TNFR2), and CCR8. They prevalently localized to perivascular areas of fibrous septa and responded to the chemoattractant activity of CCL1/I-309, which was found to be produced by either thymic medullary macrophages or fibrous septa epithelial cells. After polyclonal activation, CD4(+)CD25(+) thymocytes did not produce the cytokines interleukin (IL)-2, IL-4, IL-5, IL-13, interferon gamma, and only a very few produced IL-10, but all they expressed on their surface CTLA-4 and the majority of them also transforming growth factor (TGF)-beta1. The suppressive activity of these cells was contact dependent and associated with the lack of IL-2 receptor (IL-2R) alpha-chain (CD25) expression in target cells. Such a suppressive activity was partially inhibited by either anti-CTLA-4 or anti-TGF-beta1, and was completely blocked by a mixture of these monoclonal antibodies, which were also able to restore in target T cells the expression of IL-2R alpha-chain and, therefore, their responsiveness to IL-2. These data demonstrate that CD4(+)CD25(+) human thymocytes represent a population of regulatory cells that migrate in response to the chemokine CCL1/I-309 and exert their suppressive function via the inhibition of IL-2R alpha-chain in target T cells, induced by the combined activity of CTLA-4 and membrane TGF-beta1.     

A novel CCR5-specific pharmacodynamic assay in whole blood using phosphoflow cytometry highlights different ligand-dependent responses but similar properties of antagonists in CD8+ and CD4+ T lymphocytes

Chemokine CC motif receptor (CCR) 5 is a major drug target for both inflammation and virology indications. The primary function of CCR5 is to mediate the trafficking of CCR5-expressing lymphocytes to any of the CCR5 ligands, which are often increased during inflammatory responses. In addition, CCR5 is a coreceptor for HIV, mediating R5 tropic HIV infection of CCR5-expressing CD4 T cells. We report the use of a novel method to assay the pharmacodynamic (PD) properties of small-molecule and antibody inhibitors of CCR5 ligand-induced activation by measuring phosphorylation of serine residue 349 in the cytoplasmic tail of human CCR5 using phosphoflow cytometry in whole blood. This assay is highly specific and measures CCR5 phosphorylation in both CD8(+) and CD4(+) T cells and allows the calculation of inhibitor IC(50) values from both lymphocyte subsets in the presence of CCR5 antagonists. In addition, this assay is cross-reactive to nonhuman primates and allows PD analysis in whole blood from rhesus and cynomolgus macaque. Using this assay, we identified different ligand-dependent response properties between CD8(+) and CD4(+) T cells, although CCR5 antagonists behave with similar properties against both cell types. The use of this assay may be of particular benefit to monitor PD effects of CCR5 inhibitors during drug development, preclinical in vivo studies, and in patients currently being treated for HIV or CCR5-mediated inflammatory diseases with CCR5 inhibitors. Similar phosphoflow approaches to other GPCR targets on circulating lymphocytes may prove to be the most reliable PD assay for preclinical and potentially clinical development.     

Bone marrow CD34(+) cells and megakaryoblasts secrete beta-chemokines that block infection of hematopoietic cells by M-tropic R5 HIV

CD34(+) cells are nonpermissive to infection by HIV strains X4 and R5, despite the fact that many CD34(+) cells express high levels of the viral receptor protein CD4 and the coreceptor CXCR4 on their surface. In these cells, the co-receptor CCR5 protein, which, like CXCR4, is a chemokine receptor, is detected mainly intracellularly. We hypothesized that CD34(+) cells secrete CCR5-binding chemokines and that these factors interfere with HIV R5 interactions with these cells, possibly by binding CCR5 or by inducing its internalization. We found that human CD34(+) cells and CD34(+)KIT(+) cells, which are enriched in myeloid progenitor cells, expressed and secreted the CCR5 ligands RANTES, MIP-1alpha, and MIP-1beta and that IFN-gamma stimulated expression of these chemokines. In contrast, SDF-1, a CXCR4 ligand, was not detectable in the CD34(+)KIT(+) cells, even by RT-PCR. Conditioned media from CD34(+) cell culture significantly protected the T lymphocyte cell line PB-1 from infection by R5 but not X4 strains of HIV. Interestingly, the secretion of endogenous chemokines decreased with the maturation of CD34(+) cells, although ex vivo, expanded megakaryoblasts still secreted a significant amount of RANTES. Synthesis of CCR5-binding chemokines by human CD34(+) cells and megakaryoblasts therefore largely determines the susceptibility of these cells to infection by R5 HIV strains. We postulate that therapeutic agents that induce the endogenous synthesis of chemokines in human hematopoietic cells may protect these cells from HIV infection.     

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.     

The C-C chemokine receptors CCR4 and CCR8 identify airway T cells of allergen-challenged atopic asthmatics

In vitro polarized human Th2 cells preferentially express the chemokine receptors CCR3, CCR4, and CCR8 and migrate to their ligands: eotaxin, monocyte-derived chemokine (MDC), thymus- and activation-regulated chemokine (TARC), and I-309. We have studied the expression of chemokines and chemokine receptors in the airway mucosa of atopic asthmatics. Immunofluorescent analysis of endobronchial biopsies from six asthmatics, taken 24 hours after allergen challenge, demonstrates that virtually all T cells express IL-4 and CCR4. CCR8 is coexpressed with CCR4 on 28% of the T cells, while CCR3 is expressed on eosinophils but not on T cells. Expression of the CCR4-specific ligands MDC and TARC is strongly upregulated on airway epithelial cells upon allergen challenge, suggesting an involvement of this receptor/ligand axis in the regulation of lymphocyte recruitment into the asthmatic bronchi. In contrast to asthma, T cells infiltrating the airways of patients with chronic obstructive pulmonary disease and pulmonary sarcoidosis produce IFN-gamma and express high levels of CXCR3, while lacking CCR4 and CCR8 expression. These data support the role of CCR4, of its ligands MDC and TARC, and of CCR8 in the pathogenesis of allergen-induced late asthmatic responses and suggest that these molecules could be considered as targets for therapeutic intervention.     

CCR4-dependent regulatory T cell function in inflammatory bowel disease

Inflammatory bowel disease (IBD) is an idiopathic inflammatory disease of the intestine. CD4(+) T lymphocytes play an important role in both initiating and regulating intestinal inflammatory immune responses. CD4(+)CD25(+)CD45RB(low) regulatory T (T reg) cells are capable of preventing the development of colitis in a mouse model of IBD. The precise mechanism of T reg cell-mediated prevention of colitis in this model is unclear, and the role of chemokine receptors in the trafficking and function of T reg cells in this model has not been determined. We examined the role of the chemokine receptor CCR4 in in vivo trafficking and suppressive function of T reg cells in a mouse adoptive transfer model of IBD. CCR4-deficient T reg cells failed to accumulate in the mesenteric lymph nodes (MLNs) at early time points (2-5 d) after adoptive transfer, resulting in a failure to suppress the generation of pathogenic T cells and the development of colitis. Moreover, although CCR4-deficent T cells had equivalent in vitro suppressive activity and accumulated in MLNs at later time points (42-56 d), they were unable to suppress colitis. Our study demonstrates that CCR4 plays an important role in T reg cell trafficking in LNs and that this is critical for T reg cell suppressive function in vivo.     

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.     

Migratory properties of naive, effector, and memory CD8(+) T cells

It has been proposed that two different antigen-experienced T cell subsets may be distinguishable by their preferential ability to home to lymphoid organs (central memory cells) or nonlymphoid tissues (effector memory/effector cells). We have shown recently that murine antigen-primed CD8(+) T cells cultured in interleukin (IL)-15 (CD8(IL-15)) resemble central memory cells in phenotype and function. In contrast, primed CD8(+) T cells cultured in IL-2 (CD8(IL-2)) become cytotoxic effector cells. Here, the migratory behavior of these two subsets was investigated. Naive, CD8(IL-15) cells and, to a lesser degree, CD8(IL-2) cells localized to T cell areas in the spleen, but only naive and CD8(IL-15) cells homed to lymph nodes (LNs) and Peyer's patches. Intravital microscopy of peripheral LNs revealed that CD8(IL-15) cells, but not CD8(IL-2) cells, rolled and arrested in high endothelial venules (HEVs). Migration of CD8(IL-15) cells to LNs depended on L-selectin and required chemokines that bind CC chemokine receptor (CCR)7. Both antigen-experienced populations, but not naive T cells, responded to inflammatory chemokines and accumulated at sites of inflammation. However, CD8(IL-2) cells were 12 times more efficient in migrating to inflamed peritoneum than CD8(IL-15) cells. Furthermore, CD8(IL-15) cells proliferated rapidly upon reencounter with antigen at sites of inflammation. Thus, central memory-like CD8(IL-15) cells home avidly to lymphoid organs and moderately to sites of inflammation, where they mediate rapid recall responses, whereas CD8(IL-2) effector T cells accumulate in inflamed tissues, but are excluded from most lymphoid organs.     

CC chemokine receptor (CCR)4 and the CCR10 ligand cutaneous T cell-attracting chemokine (CTACK) in lymphocyte trafficking to inflamed skin.

The chemokine thymus and activation-regulated chemokine (TARC; CCL17) is displayed by cutaneous (but not intestinal) venules, and is thought to trigger vascular arrest of circulating skin homing memory T cells, which uniformly express the TARC receptor CC chemokine receptor (CCR)4. Cutaneous T cell-attracting chemokine (CTACK; CCL27), expressed by skin keratinocytes, also attracts cutaneous memory T cells, and is hypothesized to assist in lymphocyte recruitment to skin as well. Here we show that chronic cutaneous inflammation induces CD4 T cells expressing E-selectin binding activity (a marker of skin homing memory cells) in draining lymph node, and that these E-selectin ligand+ T cells migrate efficiently to TARC and to CTACK. In 24 h in vivo homing assays, stimulated lymph node T cells from wild-type mice or, surprisingly, from CCR4-deficient donors migrate efficiently to inflamed skin; and an inhibitory anti-CTACK antibody has no effect on wild-type lymphocyte recruitment. However, inhibition with anti-CTACK monoclonal antibody abrogates skin recruitment of CCR4-deficient T cells. We conclude that CTACK and CCR4 can both support homing of T cells to skin, and that either one or the other is required for lymphocyte recruitment in cutaneous delayed type hypersensitivity.     

致敏小鼠CD4~+ CD25~+调节性T细胞磁珠分选及体外扩增

本研究探讨致敏小鼠CD4+ CD25+调节性T细胞的分选及体外扩增。流式细胞术检测致敏小鼠及正常小鼠体内CD4+ CD25+ Treg细胞水平,免疫磁珠分选方法从小鼠脾细胞中分选出CD4+T细胞、CD4+ CD25+ Treg细胞和CD4+ CD25-T细胞,负载抗CD3/CD28单克隆抗体MACSiBead联合IL-2共同刺激CD4+ CD25+ Treg细胞进行体外扩增培养,用0.4%台盼蓝染色并计数检测细胞的活性,流式细胞术检测分选后细胞纯度、主要表面标记及Foxp3基因的表达。结果表明:致敏小鼠体内CD4+ CD25+ Treg水平较正常小鼠升高(P<0.05)。分选出CD4+ CD25+ Treg细胞纯度平均达到87%,细胞活性大于97%,高表达Foxp3基因。体外扩增2周后细胞数扩增倍数能够达到42倍,CD4+ CD25+ Treg细胞所占比例为85.32%,Foxp3表达由(76.92±1.72)%稍下降至(75.33±2.11)%(P>0.05)。结论:免疫磁珠分选法能够分选出高纯度的CD4+ CD25+ Treg细胞,该分选方法不影响分选靶细胞的细胞活力;体外成功扩增了CD4+ CD25+ Treg细胞,扩增后的CD4+ CD25+ Treg细胞表面标记及Foxp3基因表达无明显改变。     

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.     

Rapid turnover of effector-memory CD4(+) T cells in healthy humans

Memory T cells can be divided into central-memory (T(CM)) and effector-memory (T(EM)) cells, which differ in their functional properties. Although both subpopulations can persist long term, it is not known whether they are maintained by similar mechanisms. We used in vivo labeling with deuterated glucose to measure the turnover of CD4(+) T cells in healthy humans. The CD45R0(+)CCR7(-) T(EM) subpopulation was shown to have a rapid proliferation rate of 4.7% per day compared with 1.5% per day for CD45R0(+)CCR7(+) T(CM) cells; these values are equivalent to average intermitotic (doubling) times of 15 and 48 d, respectively. In contrast, the CD45RA(+)CCR7(+) naive CD4(+) T cell population was found to be much longer lived, being labeled at a rate of only 0.2% per day (corresponding to an intermitotic time of approximately 1 yr). These data indicate that human CD4(+) T(EM) cells constitute a short-lived cell population that requires continuous replenishment in vivo.     

CXC chemokine receptor 5 expression defines follicular homing T cells with B cell helper function

Leukocyte traffic through secondary lymphoid tissues is finely tuned by chemokines. We have studied the functional properties of a human T cell subset marked by the expression of CXC chemokine receptor 5 (CXCR5). Memory but not naive T cells from tonsils are CXCR5(+) and migrate in response to the B cell-attracting chemokine 1 (BCA-1), which is selectively expressed by reticular cells and blood vessels within B cell follicles. Tonsillar CXCR5(+) T cells do not respond to other chemokines present in secondary lymphoid tissues, including secondary lymphoid tissue chemokine (SLC), EBV-induced molecule 1 ligand chemokine (ELC), and stromal cell-derived factor 1 (SDF-1). The involvement of tonsillar CXCR5(+) T cells in humoral immune responses is suggested by their localization in the mantle and light zone germinal centers of B cell follicles and by the concomitant expression of activation and costimulatory markers, including CD69, HLA-DR, and inducible costimulator (ICOS). Peripheral blood CXCR5(+) T cells also belong to the CD4(+) memory T cell subset but, in contrast to tonsillar cells, are in a resting state and migrate weakly to chemokines. CXCR5(+) T cells are very inefficient in the production of cytokines but potently induce antibody production during coculture with B cells. These properties portray CXCR5(+) T cells as a distinct memory T cell subset with B cell helper function, designated here as follicular B helper T cells (T(FH)).     

CCR5-dependent homing of naturally occurring CD4+ regulatory T cells to sites of Leishmania major infection favors pathogen persistence

Pathogen persistence after clinical cure is a hallmark of many chronic infections. Previously, we showed that naturally occurring CD4+CD25+ regulatory T (nTreg) cells rapidly accumulate within chronic dermal sites of Leishmania major infection where they suppress anti-pathogen CD4+ T cell responses, favor parasite persistence and dermal pathology, and consequently control concomitant immunity. Here, we postulated that chemokines might direct nTreg cell homing in sites of infection and show that CD4+CD25+ nTreg cells, compared with normal CD4+ T cells, preferentially express the CCR5 chemokine receptor, which enables them to migrate in response to CCR5 ligands in vitro. We show that in contrast to their wild-type (WT) counterparts, CCR5-/- CD4+CD25+ nTreg cells resulted in an increased magnitude of parasite-specific, interferon gamma-producing CD4+ T cells within infection sites, dramatically reduced parasite numbers, and potent resistance to infection, a finding consistent with the clinical outcome of infected CCR5-/- mice. Interestingly, this resistance was related to an inefficient migration of CCR5-/- nTreg cells to infected dermal sites compared with WT nTreg cells. Thus, this study shows that CCR5 directs the homing of CD4+CD25+ nTreg cells to L. major-infected dermal sites where they promote the establishment of infection and long-term survival of the parasite in the immune host.     

Cooperating mechanisms of CXCR5 and CCR7 in development and organization of secondary lymphoid organs

Homeostatic chemokines participate in the development of secondary lymphoid organs and later on in the functional organization of these tissues. The development of lymph nodes (LNs) and Peyer's patches depends on the recruitment of CD3- CD4+ interleukin (IL)-7R alpha hi cells to sites of future organ development. CD3- CD4+ IL-7R alpha hi cells express the chemokine receptor CXCR5 and might be attracted by its ligand CXCL13, which is secreted by mesenchymal cells. Mesenchymal cells also secrete CCL19, a ligand for CCR7, yet it is not clear whether CCR7 and CCL19 are important for secondary lymphoid organ development. Analyzing CXCR5-/- CCR7-/- double deficient mice we now show that these mice lack all examined peripheral LNs suggesting a profound role for both receptors in secondary lymphoid organ development. We demonstrate that CD3- CD4+ IL-7R alpha hi cells express CXCR5 as well as CCR7 indicating that both receptors cooperate during an early step of secondary lymphoid organ development. Furthermore, CXCR5-/- CCR7-/- mice display a severely disturbed architecture of mesenteric LN and spleen. Due to an impaired migration of B cells into the white pulp, CXCR5-/- CCR7-/- mice fail to develop B cell follicles but show small clusters of unorganized lymphocytes in the spleen. These data demonstrate a cooperative function of CXCR5 and CCR7 in lymphoid organ organogenesis and organization.     

CCR10 expression is a common feature of circulating and mucosal epithelial tissue IgA Ab-secreting cells

The dissemination of IgA-dependent immunity between mucosal sites has important implications for mucosal immunoprotection and vaccine development. Epithelial cells in diverse gastrointestinal and nonintestinal mucosal tissues express the chemokine MEC/CCL28. Here we demonstrate that CCR10, a receptor for MEC, is selectively expressed by IgA Ab-secreting cells (large s/cIgA(+)CD38(hi)CD19(int/-)CD20(-)), including circulating IgA(+) plasmablasts and almost all IgA(+) plasma cells in the salivary gland, small intestine, large intestine, appendix, and tonsils. Few T cells in any mucosal tissue examined express CCR10. Moreover, tonsil IgA plasmablasts migrate to MEC, consistent with the selectivity of CCR10 expression. In contrast, CCR9, whose ligand TECK/CCL25 is predominantly restricted to the small intestine and thymus, is expressed by a fraction of IgA Ab-secreting cells and almost all T cells in the small intestine, but by only a small percentage of plasma cells and plasmablasts in other sites. These results point to a unifying role for CCR10 and its mucosal epithelial ligand MEC in the migration of circulating IgA plasmablasts and, together with other tissue-specific homing mechanisms, provides a mechanistic basis for the specific dissemination of IgA Ab-secreting cells after local immunization.