Evidence for NK cell subsets based on chemokine receptor expression

To help understand the role of chemokines in NK cell trafficking, we determined the chemokine receptor profiles of three different human NK cell lines and freshly isolated primary human NK cells. The cell lines overlapped in their chemokine receptor profiles: CXCR3 and CXCR4 were expressed by all three lines, whereas CCR1, CCR4, CCR6, CCR7, and CX3CR1 were expressed by only one or two of the lines, and no other chemokine receptors were detected. Freshly isolated primary NK cells were found to express CXCR1, CXCR3, and CXCR4, and to contain subsets expressing CCR1, CCR4, CCR5, CCR6, CCR7, CCR9, CXCR5, and CXCR6. With the exception of CCR4, these chemokine receptors were expressed at higher percentages by CD56(bright) NK cells than by CD56(dim) NK cells. In particular, CCR7 was expressed by almost all CD56(bright) NK cells but was not detected on CD56(dim) NK cells. CCR9 and CXCR6 have not been described previously on primary NK cells. These results indicate that within both the CD56(bright) and CD56(dim) NK cell populations, subsets with the capacity for differential trafficking programs exist, which likely influence their functions in innate and adaptive immunity.     

Mice with a selective deletion of the CC chemokine receptors 5 or 2 are protected from dextran sodium sulfate-mediated colitis: lack of CC chemokine receptor 5 expression results in a NK1.1+ lymphocyte-associated Th2-type immune response in the intestine

The chemokine receptors CCR2 and CCR5 and their respective ligands regulate leukocyte chemotaxis and activation. To determine the role of these chemokine receptors in the regulation of the intestinal immune response, we induced colitis in CCR2- and CCR5-deficient mice by continuous oral administration of dextran sodium sulfate (DSS). Both CCR2- and CCR5-deficient mice were susceptible to DSS-induced intestinal inflammation. The lack of CCR2 or CCR5 did not reduce the DSS-induced migration of macrophages into the colonic lamina propria. However, both CCR5-deficient mice and, to a lesser degree, CCR2-deficient mice were protected from DSS-induced intestinal adhesions and mucosal ulcerations. CCR5-deficient mice were characterized by a greater relative infiltration of CD4+ and NK1.1+ lymphocyte in the colonic lamina propria when compared to wild-type and CCR2-deficient mice. In CCR5-deficient mice, mucosal mRNA expression of IL-4, IL-5, and IL-10 was increased, whereas that of IFN-gamma was decreased, corresponding to a Th2 pattern of T cell activation. In CCR2-deficient mice, the infiltration of Th2-type T cells in the lamina propria was absent, but increased levels of IL-10 and decreased levels of IFN-gamma may have down regulated mucosal inflammation. Our data indicate that CCR5 may be critical for the promotion of intestinal Th1-type immune responses in mice.     

Evasion from NK cell immunity by MHC class I chain-related molecules expressing colon adenocarcinoma

Evasion of host immune responses is well documented for viruses and may also occur during tumor immunosurveillance. The mechanisms involve alterations in MHC class I expression, Ag processing and presentation, chemokine and cytokine production, and lymphocyte receptor expression. Epithelial tumors overexpress MHC class I chain-related (MIC) molecules, which are ligands for the activating receptor NKG2D on NK and T cells. We report that NK cells from patients with colorectal cancer lack expression of activating NKG2D and chemokine CXCR1 receptors, both of which are internalized. Serum levels of soluble MIC (sMIC) are elevated and are responsible for down-modulation of NKG2D and CXCR1. In contrast, high serum levels of CXC ligands, IL-8, and epithelial-neutrophil-activating peptide (ENA-78) do not down-modulate CXCR1. In vitro, internalization of NKG2D and CXCR1 occurs within 4 and 24 h, respectively, of incubating normal NK cells with sMIC-containing serum. Furthermore, natural cytotoxicity receptor NKp44 and chemokine receptor CCR7 are also down-modulated in IL-2-activated NK cells cocultured in MIC-containing serum-an effect secondary to the down-modulation of NKG2D and not directly caused by physical association with sMIC. The patients' NK cells up-regulate expression of NKG2D, NKp44, CXCR1, and CCR7 when cultured in normal serum or anti-MIC Ab-treated autologous serum. NKG2D(+) but not NKG2D(-) NK cells are tumoricidal in vitro, and in vivo they selectively traffic to the xenografted carcinoma, form immunological synapse with tumor cells, and significantly retard tumor growth in the SCID mice. These results suggest that circulating sMIC in the cancer patients deactivates NK immunity by down-modulating important activating and chemokine receptors.     

The primate lentiviral receptor Bonzo/STRL33 is coordinately regulated with CCR5 and its expression pattern is conserved between human and mouse

Chemokines play necessary and important roles in regulating the trafficking of lymphocytes to intra- or interlymphoid tissues as well as to sites of inflammation. The complex migratory patterns of lymphoid lineage cells is governed by subset-specific expression of chemokine receptors and their access to specific ligands. Several chemokine receptors and chemokine receptor-like orphan receptors also serve, in conjunction with CD4, as coreceptors for infection by human and simian immunodeficiency viruses (HIV and SIV). Here we show that the expression pattern of Bonzo/STRL33, an orphan SIV/HIV coreceptor, is highly restricted to the memory subset of T cells and is up-regulated upon stimulation of these cells with IL-2 or IL-15. Both the pattern and the regulation of Bonzo expression closely paralleled that of CC family chemokine receptors CCR5 or CCR6 and inversely correlated with CXCR4 expression. However, in striking contrast to CCR5, Bonzo expression was not down-modulated by PMA or mitogen stimulation of T cells. Targeted replacement of the Bonzo gene with a gene encoding green fluorescent protein in mice revealed that the expression and cytokine regulation of mouse Bonzo are comparable to those of its human counterpart. The similar expression and regulation patterns of Bonzo and the HIV coreceptor CCR5 may have implications for understanding the role of HIV/SIV receptors in viral evolution and pathogenesis.     

A chemokine-dependent stromal induction mechanism for aberrant lymphocyte accumulation and compromised lymphatic return in rheumatoid arthritis

According to the current model for tissue-specific homing, specificity is conferred by the selective recruitment of lymphocyte populations from peripheral blood, based on their expression of chemokine and adhesion receptors (endothelial selection). In this study, we provide evidence for an alternative stromal induction mechanism that operates in chronic inflammation. We show that the human rheumatoid synovial microenvironment directly induces functional inflammatory (CCR5 and CXCR3) and constitutive (CCR7 and CXCR4) chemokine receptors on infiltrating CD4(+) T cells. Expression of the corresponding inflammatory chemokine ligands (CCL5 and CXCL11) was confined to stromal areas in the synovium. However, expression of the constitutive ligands (CCL19 and CXCL12) was inappropriately high on both vascular and lymphatic endothelium, suggesting that the vascular to lymphatic chemokine gradient involved in lymphatic recirculation becomes subverted in the rheumatoid synovium. These results challenge the view that leukocyte trafficking is regulated solely by selective recruitment of pre-existing chemokine receptor-positive cells from peripheral blood, by providing an alternative explanation based on aberrant lymphocyte retention and compromised lymphatic return.     

Expression of the inflammatory chemokines CCL2, CCL5 and CXCL2 and the receptors CCR1-3 and CXCR2 in T lymphocytes from mammary tumor-bearing mice

Chemokines and their receptors have been studied in several solid tumor models as mediators of inflammation. In turn, inflammation has been implicated in the promotion and progression of tumors, and as such, chemokines have been proposed as novel molecular targets for chemotherapy. While the expression of these molecules has been described in tumor cells, endothelial cells, macrophages and neutrophils, less attention has been paid to the expression profile of these molecules by T lymphocytes in the periphery or infiltrating the tumor. Using the D1-DMBA-3 murine mammary adenocarcinoma model, we aimed to better characterize the differential expression of chemokines and/or their receptors in the host and in the tumor microenvironment, and specifically, in the T cells of tumor-bearing mice compared to normal control animals. We found that T lymphocytes from tumor-bearing mice express the pro-inflammatory chemokines, CCL2, CCL5 and CXCL2, as well as the chemokine receptors, CCR1, CCR2, CCR3 and CXCR2.     

CCR5 is essential for NK cell trafficking and host survival following Toxoplasma gondii infection

The host response to intracellular pathogens requires the coordinated action of both the innate and acquired immune systems. Chemokines play a critical role in the trafficking of immune cells and transitioning an innate immune response into an acquired response. We analyzed the host response of mice deficient in the chemokine receptor CCR5 following infection with the intracellular protozoan parasite Toxoplasma gondii. We found that CCR5 controls recruitment of natural killer (NK) cells into infected tissues. Without this influx of NK cells, tissues from CCR5-deficient (CCR5-/-) mice were less able to generate an inflammatory response, had decreased chemokine and interferon gamma production, and had higher parasite burden. As a result, CCR5-/- mice were more susceptible to infection with T. gondii but were less susceptible to the immune-mediated tissue injury seen in certain inbred strains. Adoptive transfer of CCR5+/+ NK cells into CCR5-/- mice restored their ability to survive lethal T. gondii infection and demonstrated that CCR5 is required for NK cell homing into infected liver and spleen. This study establishes CCR5 as a critical receptor guiding NK cell trafficking in host defense.     

Unique subpopulations of CD56+ NK and NK-T peripheral blood lymphocytes identified by chemokine receptor expression repertoire

CD56, an adhesion molecule closely related to neural cell adhesion molecule, is an immunophenotypic marker for several unique populations of PBLS: Although CD56(+) cells derive from multiple lymphocyte lineages, they share a role in immunosurveillance and antitumor responses. We have studied the chemokine receptor expression patterns and functional migratory responses of three distinct CD56(+) populations from human peripheral blood. NK-T cells were found to differ greatly from NK cells, and CD16(+) NK cells from CD16(-) NK cells. CD16(+) NK cells were the predominant population responding to IL-8 and fractalkine, whereas NK-T cells were the predominant population responding to the CCR5 ligand macrophage-inflammatory protein-1beta. CD16(-) NK cells were the only CD56(+) population that uniformly expressed trafficking molecules necessary for homing into secondary lymphoid organs through high endothelial venule. These findings describe a diverse population of cells that may have trafficking patterns entirely different from each other, and from other lymphocyte types.     

Differential upregulation of chemokine receptors on CD56+ NK cells and their transmigration to the site of infection in tuberculous pleurisy

Chemokines and their receptors orchestrate leukocyte recruitment and confer immunity during Mycobacterium tuberculosis infection. The immunoregulatory and cytotoxic activities of natural killer (NK) cells are essential at the site of infection during tuberculous pleurisy. The frequency, subtypes, and expression of phenotype markers and chemokine receptors on NK cells were assessed by flow cytometry in tuberculous (TB) and nontuberculous (NTB) pleural fluid (PF). Chemotaxis was also shown in response to chemokines. A significant decrease in CD56^dim with no change in CD56^bright NK cells was observed, while a significant increase in activation markers and Toll-like receptors (TLRs) was observed on TB-PF CD56^bright NK cells. Significantly increased expression of chemokine receptors CCR1, CCR2 and CCR7 on CD56^bright and CCR5 on CD56^dim NK cells was observed in the TB group. Transmigration of TB-PF NK cells was significantly high in response to IL-8, IP-10, MCP-1 and SLC. Transmigrated TB-NK cells showed a significant increase in CXCR2, CCR2 and CCR7 expression. The study suggests that CD56^bright NK cells may recognize M. tuberculosis directly using TLRs, HLA-DR and express CD69 as an early activation marker. In addition, CC chemokines induce activation signals in chemokine receptors mediating differential NK cell migration to the site. Thus, NK cells act as first direct sensors and effectors in mycobacterial infection.     

Targeting autophagy blocks melanoma growth by bringing natural killer cells to the tumor battlefield

Solid tumors are able to establish and sustain an immune suppressive microenvironment, which prevents the infiltration of cytotoxic effector immune cells into the tumor bed. We showed that genetic targeting of the macroautophagy/autophagy gene Becn1/Beclin1 in B16-F10 tumors inhibits their growth by inducing a massive infiltration of functional natural killer (NK) cells into the tumor bed. Such infiltration is primarily due to the ability of BECN1-defective tumor cells to overexpress and release CCL5 cytokine in the tumor microenvironment by a mechanism involving the activation of the MAPK8/JNK-JUN/c-Jun signaling pathway. Clinically, we reported a strong positive correlation between the expression of NK cell marker and CCL5 in human melanoma tumors and more importantly, a significant increased survival is found in melanoma patients expressing a high level of CCL5. Overall, these findings highlight the impact of targeting autophagy in breaking the immunosuppressive tumor microenvironment barrier, thus allowing the trafficking of cytotoxic NK cells into the tumor bed. This study underscore the importance of autophagy inhibition in tumors as a novel therapeutic strategy to fully exploit NK cells antitumor properties in clinical settings.     

Human NK cells express CC chemokine receptors 4 and 8 and respond to thymus and activation-regulated chemokine, macrophage-derived chemokine, and I-309

NK cells respond to various chemokines, suggesting that they express receptors for these chemokines. In this paper, we show that IL-2-activated NK (IANK) cells express CC chemokine receptor 4 (CCR4) and CCR8, as determined by flow cytometric, immunoblot, and RNase protection assays. Macrophage-derived chemokine (MDC), the ligand for CCR4, induces the phosphorylation of CCR4 within 0.5 min of activating IANK cells with this ligand. This is corroborated with the recruitment of G protein-coupled receptor kinases 2 and 3 and their association with CCR4 in IANK cell membranes. Also, CCR4 is internalized between 5 and 45 min but reappears in the membranes after 60 min of stimulation with MDC. MDC, thymus and activation-regulated chemokine (TARC), and I-309 induce the chemotaxis of IANK cells, an activity that is inhibited upon pretreatment of these cells with pertussis toxin, suggesting that receptors for these chemokines are coupled to pertussis toxin-sensitive G proteins. In the calcium release assay, cross-desensitization experiments showed that TARC completely desensitizes the calcium flux response induced by MDC or I-309, whereas both MDC and I-309 partially desensitize the calcium flux response induced by TARC. These results suggest that TARC utilizes CCR4 and CCR8. Our results are the first to show that IL-2-activated NK cells express CCR4 and CCR8, suggesting that these receptors are not exclusive for Th2 cells.     

Evidence of positive selection at codon sites localized in extracellular domains of mammalian CC motif chemokine receptor proteins

Background  

CC chemokine receptor proteins (CCR1 through CCR10) are seven-transmembrane G-protein coupled receptors whose signaling pathways are known for their important roles coordinating immune system responses through targeted trafficking of white blood cells. In addition, some of these receptors have been identified as fusion proteins for viral pathogens: for example, HIV-1 strains utilize CCR5, CCR2 and CCR3 proteins to obtain cellular entry in humans. The extracellular domains of these receptor proteins are involved in ligand-binding specificity as well as pathogen recognition interactions.     

High level expression, activation, and antagonism of CC chemokine receptors CCR2 and CCR3 in Chinese hamster ovary cells

The specificity of leukocyte trafficking in inflammation is controlled by the interactions of chemokines with chemokine receptors. Reliable structure-function studies of chemokine-receptor interactions would benefit from cell lines that express consistent high levels of chemokine receptors. We describe herein two new Chinese hamster ovary (CHO) cell lines in which the genes for chemokine receptors CCR2 and CCR3 have been incorporated into identical positions in the host genome. CCR2 is the primary receptor for the chemokine monocyte chemoattractant protein-1 (MCP-1) whereas CCR3 is the primary receptor for the chemokines eotaxin-1, eotaxin-2 and eotaxin-3. Both receptors are expressed at >5,000,000 copies per cell, substantially higher levels than in previous cell lines, and both are competent for binding and activation by the cognate chemokines for these receptors. Using these cell lines we confirm that eotaxin-1 and eotaxin-3 can act as an agonist and an antagonist, respectively, of CCR2. In addition, we show that eotaxin-2 is an antagonist of CCR2 and MCP-1 is an agonist of CCR3. Comparison of the chemokine sequences reveals several positions that are identical in MCP-1 and eotaxin-1 but different in eotaxin-2 and eotaxin-3, suggesting that these amino acids play a role in CCR2 activation.     

In vivo differentiated cytokine-producing CD4(+) T cells express functional CCR7

Chemokines and their receptors fulfill specialized roles in inflammation and under homeostatic conditions. CCR7 and its ligands, CCL19 and CCL21, are involved in lymphocyte recirculation through secondary lymphoid organs and additionally navigate lymphocytes into distinct tissue compartments. The role of CCR7 in the migration of polarized T effector/memory cell subsets in vivo is still poorly understood. We therefore analyzed murine and human CD4(+) cytokine-producing cells developed in vivo for their chemotactic reactivity to CCR7 ligands. The responses of cells producing cytokines, such as IFN-gamma, IL-4, and IL-10, as well as of subsets defined by memory or activation markers were comparable to that of naive CD4(+) cells, with slightly lower reactivity in cells expressing IL-10 or CD69. This indicates that CCR7 ligands are able to attract naive as well as the vast majority of activated and effector/memory T cell stages. Chemotactic reactivity of these cells toward CCL21 was absent in CCR7-deficient cells, proving that effector cells do not use alternative receptors for this chemokine. Th1 cells generated from CCR7(-/-) mice failed to enter lymph nodes and Peyer's patches, but did enter a site of inflammation. These findings indicate that CD4(+) cells producing effector cytokines upon stimulation retain the capacity to recirculate through lymphoid tissues via CCR7.     

Chemokine receptor trio: CXCR3, CXCR4 and CXCR7 crosstalk via CXCL11 and CXCL12

Although chemokines are well established to function in immunity and endothelial cell activation and proliferation, a rapidly growing literature suggests that CXC Chemokine receptors CXCR3, CXCR4 and CXCR7 are critical in the development and progression of solid tumors. The effect of these chemokine receptors in tumorigenesis is mediated via interactions with shared ligands I-TAC (CXCL11) and SDF-1 (CXCL12). Over the last decade, CXCR4 has been extensively reported to be overexpressed in most human solid tumors and has earned considerable attention toward elucidating its role in cancer metastasis. To enrich the existing armamentarium of anti-cancerous agents, many inhibitors of CXCL12–CXCR4 axis have emerged as additional or alternative agents for neo-adjuvant treatments and even many of them are in preclinical and clinical stages of their development. However, the discovery of CXCR7 as another receptor for CXCL12 with rather high binding affinity and recent reports about its involvement in cancer progression, has questioned the potential of “selective blockade” of CXCR4 as cancer chemotherapeutics. Interestingly, CXCR7 can also bind another chemokine CXCL11, which is an established ligand for CXCR3. Recent reports have documented that CXCR3 and their ligands are overexpressed in different solid tumors and regulate tumor growth and metastasis. Therefore, it is important to consider the interactions and crosstalk between these three chemokine receptors and their ligand mediated signaling cascades for the development of effective anti-cancer therapies. Emerging evidence also indicates that these receptors are differentially expressed in tumor endothelial cells as well as in cancer stem cells, suggesting their direct role in regulating tumor angiogenesis and metastasis. In this review, we will focus on the signals mediated by this receptor trio via their shared ligands and their role in tumor growth and progression.     

Dendritic cells support sequential reprogramming of chemoattractant receptor profiles during naive to effector T cell differentiation

T cells undergo chemokine receptor switches during activation and differentiation in secondary lymphoid tissues. Here we present evidence that dendritic cells can induce changes in T cell expression of chemokine receptors in two continuous steps. In the first switch over a 4-5 day period, dendritic cells up-regulate T cell expression of CXCR3 and CXCR5. Additional stimulation leads to the second switch: down-regulation of lymphoid tissue homing related CCR7 and CXCR5, and up-regulation of Th1/2 effector tissue-targeting chemoattractant receptors such as CCR4, CCR5, CXCR6, and CRTH2. We show that IL-4 and IL-12 can determine the fate of the secondary chemokine receptor switch. IL-4 enhances the generation of CCR4(+) and CRTH2(+) T cells, and suppresses the generation of CXCR3(+) T cells and CCR7(-) T cells, while IL-12 suppresses the level of CCR4 in responding T cells. Furthermore, IL-4 has positive effects on generation of CXCR5(+) and CCR7(+) T cells during the second switch. Our study suggests that the sequential switches in chemokine receptor expression occur during naive T cell interaction with dendritic cells. The first switch of T cell chemokine receptor expression is consistent with the fact that activated T cells migrate within lymphoid tissues for interaction with B and dendritic cells, while the second switch predicts the trafficking behavior of effector T cells away from lymphoid tissues to effector tissue sites.     

Flip-flops of natural killer cells in autoimmune diseases versus cancers: Immunologic axis

Natural killer (NK) cells play an essential role in the immune response to infections, inflammations, and malignancies. Recent studies suggest that NK cell surface receptors and cytokines are the key points of the disease development and protection. We hypothesized that the interactions between NK cell receptors and targeted cells construct an eventual niche, and this niche has an eventual profile in various autoimmune diseases and cancers. The NK cells preactivated with cytokines, such as interleukin-2 (IL-2), IL-12, IL-15, and IL-18 can have higher cytotoxicity; however, the toxic side effect of IL-2 should be considered. The vicissitudes of NK cell profile and its receptors obey the environmental communications and cell interactions. Our vision around the NK cells as an immune axis remained dual, and we still cannot judge the immune responses based on the NK cell flip-flop. A design of eventual niche to monitor the NK cell and targeted cell interaction is needed to strengthen our ability in diagnosis and treatment approaches based on the NK cells. Here, we have reviewed the shifts in the NK cells and their surface receptors in autoimmune diseases, solid tumors, and leukemia, and also discussed the effective chemokines that affect NK cell activation and proliferation. The main aim of this review is to present a broader vision of the NK cell changes in autoimmune disease and cancers.     

CCR4 and CCR10 are expressed on epidermal keratinocytes and are involved in cutaneous immune reaction

CC chemokine ligand (CCL)17 and CCL27 produced by epidermal keratinocytes (KCs) recruit CC chemokine receptor (CCR)4 and CCR10 expressing T cells into the skin, respectively, resulting in enhanced skin inflammation. However, CCR4/CCL17 and CCR10/CCL27 interactions in epidermal KCs have not been investigated. The purpose of this study was to evaluate the role of the CCR4/CCL17 and CCR10/CCL27 loops in cutaneous immune reaction. Normal human KCs (NHKs) and HaCaT KCs expressed both CCR4 and CCR10 at mRNA and protein levels. CCR4 ligand CCL17 but not CCR10 ligand CCL27 induced production of IL-12 p40, granulocyte/monocyte colony-stimulating factor (GM-CSF) and nerve growth factor (NGF) by KCs. Both CCL17 and CCL27 induced migration of KCs in Boyden chamber assay and wound scratch assay. This study revealed that CCR4 and CCR10 are expressed on epidermal KCs and that both are functional in terms of skin cytokine production and/or migration to their ligand CCL17 and CCL27, respectively. Thus this study provided new insight into chemokine/chemokine receptors of KCs.     

Targeting activity of a TCR/IL-2 fusion protein against established tumors

We have previously reported that a single-chain T cell receptor/IL-2 fusion protein (scTCR-IL2) exhibits potent targeted antitumor activity in nude mice bearing human tumor xenografts that display cognate peptide/HLA complexes. In this study, we further explore the mechanism of action of this molecule. We compared the biological activities of c264scTCR-IL2, a scTCR-IL2 protein recognizing the aa264–272 peptide of human p53, with that of MART-1scTCR-IL2, which recognizes the MART-1 melanoma antigen (aa27–35). In vitro studies showed that c264scTCR-IL2 and MART-1scTCR-IL2 were equivalent in their ability to bind cell-surface IL-2 receptors and stimulate NK cell responses. In mice, MART-1scTCR-IL2 was found to have a twofold longer serum half-life than c264scTCR-IL2. However, despite its shorter serum half-life, c264scTCR-IL2 showed significantly better antitumor activity than MART-1scTCR-IL2 against p53⁺/HLA-A2⁺ tumor xenografts. The more potent antitumor activity of c264scTCR-IL2 correlated with an enhanced capacity to promote NK cell infiltration into tumors. Similar differences in antigen-dependent tumor infiltration were observed with activated splenocytes pre-treated in vitro with c264scTCR-IL2 or MART-1scTCR-IL2 and then transferred into p53⁺/HLA-A2⁺ tumor bearing recipients. The data support a model where c264scTCR-IL2 activates immune cells to express IL-2 receptors. Following stable interactions with cell-surface IL-2 receptors, c264scTCR-IL2 fusion molecule enhances the trafficking of immune cells to tumors displaying target peptide/HLA complexes where the immune cells mediate antitumor effects. Thus, this type of fusion molecule could be used directly as a targeted immunotherapeutic or in adoptive cell transfer approaches to activate and improve the anti-cancer activities of immune cells by providing them with pre-selected antigen recognition capability.     

Cutting edge: vasoactive intestinal peptide acts as a potent suppressor of inflammation in vivo by trans-deactivating chemokine receptors

Chemokines mediate trafficking of leukocytes to sites of inflammation and immune responses through activation of G protein-coupled receptors, which thereby provide appealing targets for novel anti-inflammatory agents. Vasoactive intestinal peptide (VIP) is an immunosuppressive neurotransmitter. We show that VIP inhibited the function of chemokine receptors on monocytes and CD4(+) T lymphocytes, with impaired chemotaxis and calcium flux in response to the cognate chemokine ligands CXCL12, CCL3, CCL4, and CCL5. This was mediated by VIP receptor type 1 and was not caused by chemokine receptor internalization. However, VIP caused dose-dependent phosphorylation of the chemokine receptor CCR5. This trans-deactivation process was studied in a murine model of delayed-type hypersensitivity: continuous infusion of VIP resulted in significant abrogation of monocyte and lymphocyte infiltration. Circulating mononuclear cells from VIP-infused mice were unable to respond to chemokines. VIP may provide a novel approach to treatment of inflammatory diseases through inhibition of chemokine-dependent leukocyte recruitment.