B Lymphocyte-Derived CCL7 Augments Neutrophil and Monocyte Recruitment, Exacerbating Acute Kidney Injury.

Acute kidney injury (AKI) is a serious condition affecting one fifth of hospital inpatients. B lymphocytes have immunological functions beyond Ab production and may produce cytokines and chemokines that modulate inflammation. In this study, we investigated leukocyte responses in a mouse model of AKI and observed an increase in circulating and kidney B cells, particularly a B220low subset, following AKI. We found that B cells produce the chemokine CCL7, with the potential to facilitate neutrophil and monocyte recruitment to the injured kidney. Siglec-G-deficient mice, which have increased numbers of B220low innate B cells and a lower B cell activation threshold, had increased Ccl7 transcripts, increased neutrophil and monocyte numbers in the kidney, and more severe AKI. CCL7 blockade in mice reduced myeloid cell infiltration into the kidney and ameliorated AKI. In two independent cohorts of human patients with AKI, we observed significantly higher CCL7 transcripts compared with controls, and in a third cohort, we observed an increase in urinary CCL7 levels in AKI, supporting the clinical importance of this pathway. Together, our data suggest that B cells contribute to early sterile inflammation in AKI via the production of leukocyte-recruiting chemokines.

CCL7 Signaling in the Tumor Microenvironment.

The tumor microenvironment is the primary location in which tumor cells and the host immune system interact. There are many physiological, biochemical, cellular mechanisms in the neighbor of tumor which is composed of various cell types. Interactions of chemokines and chemokine receptors can recruit immune cell subsets into the tumor microenvironment. These interactions can modulate tumor progression and metastasis. In this chapter, we will focus on chemokine (C-C motif) ligand 7 (CCL7) that is highly expressed in the tumor microenvironment of various cancers, including colorectal cancer, breast cancer, oral cancer, renal cancer, and gastric cancer. We reviewed how CCL7 can affect cancer immunity and tumorigenesis by describing its regulation and roles in immune cell recruitment and stromal cell biology.

Role of CCL7 in Type I Hypersensitivity Reactions in Murine Experimental Allergic Conjunctivitis.

Molecules that are necessary for ocular hypersensitivity reactions include the receptors CCR1 and CCR3; CCL7 is a ligand for these receptors. Therefore, we explored the role of CCL7 in mast cell activity and motility in vitro and investigated the requirement for CCL7 in a murine model of IgE-mediated allergic conjunctivitis. For mast cells treated with IgE and Ag, the presence of CCL7 synergistically enhanced degranulation and calcium influx. CCL7 also induced chemotaxis in mast cells. CCL7-deficient bone marrow-derived mast cells showed decreased degranulation following IgE and Ag treatment compared with wild-type bone marrow-derived mast cells, but there was no difference in degranulation when cells were activated via an IgE-independent pathway. In vivo, CCL7 was upregulated in conjunctival tissue during an OVA-induced allergic response. Notably, the early-phase clinical symptoms in the conjunctiva after OVA challenge were significantly higher in OVA-sensitized wild-type mice than in control challenged wild-type mice; the increase was suppressed in CCL7-deficient mice. In the OVA-induced allergic response, the numbers of conjunctival mast cells were lower in CCL7-deficient mice than in wild-type mice. Our results demonstrate that CCL7 is required for maximal OVA-induced ocular anaphylaxis, mast cell recruitment in vivo, and maximal FcεRI-mediated mast cell activation in vitro. A better understanding of the role of CCL7 in mediating ocular hypersensitivity reactions will provide insights into mast cell function and novel treatments for allergic ocular diseases.

Otitis Media and Nasopharyngeal Colonization in ccl3-/- Mice.

We previously found CC chemokine ligand 3 (CCL3) to be a potent effector of inflammation during otitis media (OM): exogenous CCL3 rescues the OM phenotype of tumor necrosis factor-deficient mice and the function of macrophages deficient in several innate immune molecules. To further delineate the role of CCL3 in OM, we evaluated middle ear (ME) responses of ccl3-/-mice to nontypeable Haemophilus influenzae (NTHi). CCL chemokine gene expression was evaluated in wild-type (WT) mice during the complete course of acute OM. OM was induced in ccl3-/- and WT mice, and infection and inflammation were monitored for 21 days. Phagocytosis and killing of NTHi by macrophages were evaluated by an in vitro assay. The nasopharyngeal bacterial load was assessed in naive animals of both strains. Many CCL genes showed increased expression levels during acute OM, with CCL3 being the most upregulated, at levels 600-fold higher than the baseline. ccl3-/- deletion compromised ME bacterial clearance and prolonged mucosal hyperplasia. ME recruitment of leukocytes was delayed but persisted far longer than in WT mice. These events were linked to a decrease in the macrophage capacity for NTHi phagocytosis and increased nasopharyngeal bacterial loads in ccl3-/- mice. The generalized impairment in inflammatory cell recruitment was associated with compensatory changes in the expression profiles of CCL2, CCL7, and CCL12. CCL3 plays a significant role in the clearance of infection and resolution of inflammation and contributes to mucosal host defense of the nasopharyngeal niche, a reservoir for ME and upper respiratory infections. Therapies based on CCL3 could prove useful in treating or preventing persistent disease.

CCL7 and IRF-7 Mediate Hallmark Inflammatory and IFN Responses following Rhinovirus 1B Infection.

Rhinovirus (RV) infections are common and have the potential to exacerbate asthma. We have determined the lung transcriptome in RV strain 1B-infected naive BALB/c mice (nonallergic) and identified CCL7 and IFN regulatory factor (IRF)-7 among the most upregulated mRNA transcripts in the lung. To investigate their roles we employed anti-CCL7 Abs and an IRF-7-targeting small interfering RNA in vivo. Neutralizing CCL7 or inhibiting IRF-7 limited neutrophil and macrophage influx and IFN responses in nonallergic mice. Neutralizing CCL7 also reduced activation of NF-κB p65 and p50 subunits, as well as airway hyperreactivity (AHR) in nonallergic mice. However, neither NF-κB subunit activation nor AHR was abolished with infection of allergic mice after neutralizing CCL7, despite a reduction in the number of neutrophils, macrophages, and eosinophils. IRF-7 small interfering RNA primarily suppressed IFN-α and IFN-ß levels during infection of allergic mice. Our data highlight a pivotal role of CCL7 and IRF-7 in RV-induced inflammation and IFN responses and link NF-κB signaling to the development of AHR.

Maintenance of Mycobacterium tuberculosis-specific T cell responses in End Stage Renal Disease (ESRD) and implications for diagnostic efficacy.

End-stage renal disease (ESRD) patients exhibit elevated risk of tuberculosis (TB) reactivation, but current diagnostics, including the interferon gamma release assay (IGRA), exhibit poor sensitivity in ESRD. We tested 80 ESRD patients and found an 18.75% prevalence of IGRA positivity. A subset of patients was assessed for Mtb-specific expression of 44 cytokines/chemokines, and CD4+ T cell phenotype and function. Similar to non-ESRD IGRA+ individuals, Mtb-specific IFNγ, IL-1RA, IP-10, MCP-3 and IL-2 responses were identified in the ESRD IGRA+ group. 27% of the ESRD IGRA- group exhibited MCP-3 or IL-2 Mtb-specific responses, which may identify cases of latent TB infection in ESRD. Stimulation of PBMC with PPD demonstrated similar CD4+ T cell production of IFNγ, TNFα and GM-CSF by ESRD patients. The reported low sensitivity of the IGRA in ESRD cohorts is therefore unlikely to be due to poor T cell cytokine secretion, and may instead reflect defects in antigen presentation.

Characterization of conventional and atypical receptors for the chemokine CCL2 on mouse leukocytes.

Chemokine-directed leukocyte migration is crucial for effective immune and inflammatory responses. Conventional chemokine receptors (cCKRs) directly control cell movement; atypical chemokine receptors (ACKRs) regulate coexpressed cCKRs; and both cCKRs and ACKRs internalize chemokines to limit their abundance in vivo, a process referred to as scavenging. A leukocyte's migratory and chemokine-scavenging potential is determined by which cCKRs and ACKRs it expresses, and by the ligand specificity, signaling properties, and chemokine internalization capacity of these receptors. Most chemokines can bind at least one cCKR and one ACKR. CCL2 can bind to CCR2 (a cCKR) and two ACKRs (ACKR1 and ACKR2). In this study, by using fluorescent CCL2 uptake to label cells bearing functional CCL2 receptors, we have defined the expression profile, scavenging activity, and ligand specificity of CCL2 receptors on mouse leukocytes. We show that qualitative and quantitative differences in the expression of CCR2 and ACKR2 endow individual leukocyte subsets with distinctive CCL2 receptor profiles and CCL2-scavenging capacities. We reveal that some cells, including plasmacytoid dendritic cells, can express both CCR2 and ACKR2; that Ly6C(high) monocytes have particularly strong CCL2-scavenging potential in vitro and in vivo; and that CCR2 is a much more effective CCL2 scavenger than ACKR2. We confirm the unique, overlapping, ligand specificities of CCR2 and ACKR2 and, unexpectedly, find that cell context influences the interaction of CCL7 and CCL12 with CCR2. Fluorescent chemokine uptake assays were instrumental in providing these novel insights into CCL2 receptor biology, and the sensitivity, specificity, and versatility of these assays are discussed.

IL-33-induced hematopoietic stem and progenitor cell mobilization depends upon CCR2.

IL-33 has been implicated in the pathogenesis of asthma, atopic allergy, anaphylaxis, and other inflammatory diseases by promoting the production of proinflammatory cytokines and chemokines or Th2 immune responses. In this study, we analyzed the in vivo effect of IL-33 administration. IL-33 markedly promoted myelopoiesis in the bone marrow and myeloid cell emigration. Concomitantly, IL-33 induced hematopoietic stem and progenitor cell (HSPC) mobilization and extramedullary hematopoiesis. HSPC mobilization was mediated mainly through increased levels of CCL7 produced by vascular endothelial cells in response to IL-33. In vivo treatment of IL-33 rapidly induced phosphorylation of ERK, JNK, and p38, and inhibition of these signaling molecules completely blocked the production of CCL7 induced by IL-33. Consistently, inhibitor of CCR2 markedly reduced IL-33-mediated HSPC mobilization in vivo and migration of HSPCs in response to CCL7 in vitro. IL-33-mobilized HSPCs were capable of homing to, and of long-term reconstitution in, the bone marrow of irradiated recipients. Immune cells derived from these recipients had normal antifungal activity. The ability of IL-33 to promote migration of HSPCs and myeloid cells into the periphery and to regulate their antifungal activity represents a previously unrecognized role of IL-33 in innate immunity. These properties of IL-33 have clinical implications in hematopoietic stem cell transplantation.

Extramedullary myelopoiesis in malaria depends on mobilization of myeloid-restricted progenitors by IFN-γ induced chemokines.

Resolution of a variety of acute bacterial and parasitic infections critically relies on the stimulation of myelopoiesis leading in cases to extramedullary hematopoiesis. Here, we report the isolation of the earliest myeloid-restricted progenitors in acute infection with the rodent malaria parasite, Plasmodium chabaudi. The rapid disappearance of these infection-induced myeloid progenitors from the bone marrow (BM) equated with contraction of the functional myeloid potential in that organ. The loss of BM myelopoiesis was not affected by the complete genetic inactivation of toll-like receptor signaling. De-activation of IFN-γ signaling completely abrogated the contraction of BM myeloid progenitors. Radiation chimeras of Ifngr1-null and control BM revealed that IFN-γ signaling in an irradiation-resistant stromal compartment was crucial for the loss of early myeloid progenitors. Systemic IFN-γ triggered the secretion of C-C motif ligand chemokines CCL2 and CCL7 leading to the egress of early, myeloid-committed progenitors from the bone marrow mediated by their common receptor CCR2. The mobilization of myeloid progenitors initiated extramedullary myelopoiesis in the spleen in a CCR2-dependent manner resulting in augmented myelopoiesis during acute malaria. Consistent with the lack of splenic myelopoiesis in the absence of CCR2 we observed a significant persistence of parasitemia in malaria infected CCR2-deficient hosts. Our findings reveal how the activated immune system mobilizes early myeloid progenitors out of the BM thereby transiently establishing myelopoiesis in the spleen in order to contain and resolve the infection locally.

Co-administration of antigen with chemokine MCP-3 or MDC/CCL22 enhances DNA vaccine potency.

We evaluated the utility of chemokine MCP-3 and MDC/CCL22 as molecular adjuvants of DNA vaccines for botulinum neurotoxin serotype A (BoNT/A) in a Balb/c mouse model. Notably, the immunogenicity of the DNA vaccine against BoNT/A was not enhanced using a fusion of the AHc-C antigen with the MCP-3 or MDC/CCL22. Nevertheless, the potency of the DNA vaccine was significantly modulated and enhanced by co-administration of the AHc-C antigen with MCP-3 or MDC/CCL22. This strategy elicited high levels of humoral immune responses and protection against BoNT/A. The enhanced potency was further boosted by co-administration of the AHc-C antigen with both MCP-3 and MDC/CCL22 in Balb/c mice, but not by co-administration of AHc-C antigen with the MCP-3-MDC/CCL22 fusion. Co-immunization with both the MCP-3 and MDC/CCL22 constructs induced the highest levels of humoral immunity and protective potency against BoNT/A. Our results indicated that MCP-3 and MDC/CCL22 are effective molecular adjuvants of the immune responses induced by the AHc-C-expressing DNA vaccine when delivered by co-administration of the individual chemokines, but not when delivered in the form of a chemokine/antigen fusion. Thus, we describe an alternative strategy to the design and optimization of DNA vaccine constructs based on co-administration of the antigen with the chemokine rather than in the form of a chemokine/antigen fusion.

Plasma Chemokine signature correlates with lung goblet cell hyperplasia in smokers with and without chronic obstructive pulmonary disease.

BACKGROUND: Chronic Obstructive Pulmonary Disease (COPD) is characterized by lung and systemic inflammation as well as airway goblet cell hyperplasia (GCH). Mucin production is activated in part by stimulation of the epidermal growth factor (EGF) receptor pathway through neutrophils and macrophages. How circulating cytokine levels relate to GCH is not clear. METHODS: We performed phlebotomy and bronchoscopy on 25 subjects (six nonsmokers, 11 healthy smokers, and eight COPD subjects FEV1 30-60 %). Six endobronchial biopsies per subject were performed. GCH was measured by measuring mucin volume density (MVD) using stereological techniques on periodic acid fast-Schiff stained samples. We measured the levels of chemokines CXCL8/IL-8, CCL2/MCP-1, CCL7/MCP-3, CCL22/MCD, CCL3/MIP-1α, and CCL4/MIP-1ß, and the cytokines IL-1, IL-4, IL-6, IL-9, IL-17, EGF, and vascular endothelial growth factor (VEGF). Differences between groups were assessed using one-way ANOVA, t test, or Chi squared test. Post hoc tests after ANOVA were performed using Bonferroni correction. RESULTS: MVD was highest in healthy smokers (27.78 ± 10.24 µL/mm(2)) compared to COPD subjects (16.82 ± 16.29 µL/mm(2), p = 0.216) and nonsmokers (3.42 ± 3.07 µL/mm(2), p < 0.0001). Plasma CXCL8 was highest in healthy smokers (11.05 ± 8.92 pg/mL) compared to nonsmokers (1.20 ± 21.92 pg/mL, p = 0.047) and COPD subjects (6.01 ± 5.90 pg/mL, p = 0.366). CCL22 and CCL4 followed the same trends. There were no significant differences in the other cytokines measured. When the subjects were divided into current smokers (healthy smokers and COPD current smokers) and non/ex-smokers (nonsmokers and COPD ex-smokers), plasma CXCL8, CCL22, CCL4, and MVD were greater in current smokers. No differences in other cytokines were seen. Plasma CXCL8 moderately correlated with MVD (r = 0.552, p = 0.003). DISCUSSION: In this small cohort, circulating levels of the chemokines CXCL8, CCL4, and CCL22, as well as MVD, attain the highest levels in healthy smokers compared to nonsmokers and COPD subjects. These findings seem to be driven by current smoking and are independent of airflow obstruction. CONCLUSIONS: These data suggest that smoking upregulates a systemic pattern of neutrophil and macrophage chemoattractant expression, and this correlates significantly with the development of goblet cell hyperplasia.

Early induction of CCL7 downstream of TLR9 signaling promotes the development of robust immunity to cryptococcal infection.

We investigated mechanisms by which TLR9 signaling promoted the development of the protective response to Cryptococcus neoformans in mice with cryptococcal pneumonia. The afferent (week 1) and efferent (week 3) phase immune parameters were analyzed in the infected wild-type (TLR9(+/+)) and TLR-deficient (TLR9(-/-)) mice. TLR9 deletion diminished 1) accumulation and activation of CD11b(+) dendritic cells (DCs), 2) the induction of IFN-γ and CCR2 chemokines CCL7, CCL12, but not CCL2, at week 1, and 3) pulmonary accumulation and activation of the major effector cells CD4(+) and CD8(+) T cells, CD11b(+) lung DCs, and exudate macrophages at week 3. The significance of CCL7 induction downstream of TLR9 signaling was investigated by determining whether CCL7 reconstitution would improve immunological parameters in C. neoformans-infected TLR9(-/-) mice. Early reconstitution with CCL7 1) improved accumulation and activation of CD11b(+) DCs at week 1, 2) restored early IFN-γ production in the lungs, and 3) restored the accumulation of major effector cell subsets. CCL7 administration abolished the difference in lung fungal burdens between TLR9(+/+) and TLR9(-/-) mice at week 3; however, significant reduction of fungal burdens between PBS- and CCL7-treated mice has not been observed, suggesting that additional mechanism(s) apart from early CCL7 induction contribute to optimal fungal clearance in TLR9(+/+) mice. Collectively, we show that TLR9 signaling during the afferent phase contributes to the development of protective immunity by promoting the early induction of CCL7 and IFN-γ and the subsequent early recruitment and activation of DCs and additional effector cells in mice with cryptococcal pneumonia.

Macrophage/epithelial cell CCL2 contributes to rhinovirus-induced hyperresponsiveness and inflammation in a mouse model of allergic airways disease.

Human rhinovirus (HRV) infections lead to exacerbations of lower airways disease in asthmatic patients but not in healthy individuals. However, underlying mechanisms remain to be completely elucidated. We hypothesized that the Th2-driven allergic environment enhances HRV-induced CC chemokine production, leading to asthma exacerbations. Ovalbumin (OVA)-sensitized and -challenged mice inoculated with HRV showed significant increases in the expression of lung CC chemokine ligand (CCL)-2/monocyte chemotactic protein (MCP)-1, CCL4/macrophage inflammatory protein (MIP)-1ß, CCL7/MCP-3, CCL19/MIP-3ß, and CCL20/MIP3α compared with mice treated with OVA alone. Inhibition of CCL2 with neutralizing antibody significantly attenuated HRV-induced airways inflammation and hyperresponsiveness in OVA-treated mice. Immunohistochemical stains showed colocalization of CCL2 with HRV in epithelial cells and CD68-positive macrophages, and flow cytometry showed increased CCL2(+), CD11b(+) cells in the lungs of OVA-treated, HRV-infected mice. Compared with lung macrophages from naïve mice, macrophages from OVA-exposed mice expressed significantly more CCL2 in response to HRV infection ex vivo. Pretreatment of mouse lung macrophages and BEAS-2B human bronchial epithelial cells with interleukin (IL)-4 and IL-13 increased HRV-induced CCL2 expression, and mouse lung macrophages from IL-4 receptor knockout mice showed reduced CCL2 expression in response to HRV, suggesting that exposure to these Th2 cytokines plays a role in the altered HRV response. Finally, bronchoalveolar macrophages from children with asthma elaborated more CCL2 upon ex vivo exposure to HRV than cells from nonasthmatic patients. We conclude that CCL2 production by epithelial cells and macrophages contributes to HRV-induced airway hyperresponsiveness and inflammation in a mouse model of allergic airways disease and may play a role in HRV-induced asthma exacerbations.

Inducible IL10(+) suppressor B cells inhibit CNS inflammation and T helper 17 polarization.

Granulocyte-macrophage colony-stimulating factor (GMCSF) and MCP3 (aka CCL7) exert complementary, nonoverlapping, proimmune effects on responsive lymphoid and myeloid cells. We hypothesized that a synthetic cytokine linking GMCSF to MCP3 (hereafter GMME3) as part of a single polypeptide would acquire novel, therapeutically desirable immunomodulatory properties. We demonstrate that GMME3 has enhanced CC-chemokine receptor (CCR)-mediated intracellular Ca(++) mobilization with selective effects on the CD21(hi)CD24(hi) CD1.d(hi) subset of splenic B cells inducing substantial interleukin 10 (IL10) production. We demonstrate that B(GMME3) exert their suppressive effect through an IL10-mediated inhibition of antigen presentation. More importantly, B(GMME3) inhibit the reactivation of encephalomyelitis (EAE)-derived or TGFß/IL6 differentiated Th17 cells by altering their polarization toward a Th1 or Th2 phenotype. The secretion of interferon-γ (IFNγ) and IL4 in turn inhibits IL17 production. The adoptive transfer of B(GMME3), but not IL10(-/-) B(GMME3) cells, to mice symptomatic with experimental autoimmune encephalitis significantly improves their disease score and inhibits lymphoid infiltration into the central nervous system (CNS). We propose that designed CCR modulators such as GMME3, allows for conversion of naive B-cells to a novel suppressor phenotype allowing for the personalized cell therapy of autoimmune ailments.

Reduced degradation of the chemokine MCP-3 by matrix metalloproteinase-2 exacerbates myocardial inflammation in experimental viral cardiomyopathy.

BACKGROUND: Myocarditis is an important cause for cardiac failure, especially in younger patients, followed by the development of cardiac dysfunction and death. The present study investigated whether gene deletion of matrix metalloproteinase-2 influences cardiac inflammation and function in murine coxsackievirus B3 (CVB3)-induced myocarditis. METHODS AND RESULTS: Matrix metalloproteinase-2 knockout mice (MMP-2(-/-)) and their wild-type controls (WT) were infected with CVB3 to induce myocarditis. Three days after infection, an increased invasion of CD4(+)-activated T cells into the myocardium was documented, followed by an excess of inflammatory cells 7 days after infection, which was significantly higher in the MMP-2(-/-)animals compared with the WT animals. Moreover, cardiac apoptosis, remodeling, viral load, and function were deteriorated in MMP-2(-/-) animals after CVB3 infection. This overwhelming inflammation was followed by 100% mortality after 15 days. This was associated with increased levels of MCP-3 in the cardiac tissue of MMP-2(-/-) mice. Because MMP-2 cleaves the chemokine MCP-3, the loss of this cleavage lead to an overreaction of the immune system with pronounced myocardial damage mediated by the inflammatory cells. When a neutralizing antibody against MCP-3 was given to MMP-2(-/-) mice, this exaggerated reaction of the immune system could be normalized to levels similar to WT-CVB3 animals. CONCLUSIONS: Loss of MMP-2 increased the inflammatory response after CVB3 infection, which impaired cardiac function and survival during CVB3-induced myocarditis. Matrix metalloproteinase-2-mediated chemokine cleavage has an important role in cardiac inflammation as a negative feedback mechanism.

Antitumoral activity of parvovirus-mediated IL-2 and MCP-3/CCL7 delivery into human pancreatic cancer: implication of leucocyte recruitment.

Pancreatic ductal adenocarcinoma (PDAC) represents the fourth leading cause of cancer-related death in western countries. The patients are often diagnosed in advanced metastatic stages, and the prognosis remains extremely poor with an overall 5-year survival rate less than 5 %. Currently, novel therapeutic strategies are being pursued to combat PDAC, including oncolytic viruses, either in their natural forms or armed with immunostimulatory molecules. Natural killer cells are critical players against tumours and infected cells. Recently, we showed that IL-2-activated human NK cells displayed killing activity against PDAC cells, which could further be enhanced through the infection of PDAC cells with the rodent parvovirus H-1PV. In this study, the therapeutic efficacy of parvovirus-mediated delivery of three distinct cyto/chemokines (Il-2, MCP-3/CCL7 and IP-10/CXCL10) was evaluated in xenograft models of human PDAC. We show here that activated NK and monocytic cells were found to be recruited by PDAC tumours upon infection with parvoviruses armed with IL-2 or the chemokine MCP-3/CCL7, resulting in a strong anti-tumour response.

Identification of genes and proteins specifically regulated by costimulation of mast cell Fcε Receptor I and chemokine receptor 1.

Mast cell function is a critical component of allergic reactions. Mast cell responses mediated by the high-affinity immunoglobulin E receptor FcεRI can be enhanced by co-activation of additional receptors such as CC chemokine receptor 1 (CCR1). To examine the downstream effects of FcεRI-CCR1 costimulation, rat basophilic leukemia cells stably transfected with CCR1 (RBL-CCR1 cells) were sensitized and activated with antigen and/or the CCR1 ligand CC chemokine ligand (CCL) 3. Gene and protein expression were determined at 3h and 24h post-activation, respectively, using GeneChip and Luminex bead assays. Gene microarray analysis demonstrated that 32 genes were differentially regulated in response to costimulation, as opposed to stimulation with antigen or CCL3 alone. The genes most significantly up-regulated by FcεRI-CCR1 costimulation were Ccl7, Rgs1, Emp1 and RT1-S3. CCL7 protein was also expressed at higher levels 24h after dual receptor activation, although RGS1, EMP1 and RT1-S3 were not. Of the panel of chemokines and cytokines tested, only CCL2, CCL7 and interleukin (IL)-6 were expressed at higher levels following costimulation. IL-6 expression was seen only after FcεRI-CCR1 costimulation, although the amount expressed was very low. CCL7, CCL2 and IL-6 might play roles in mast cell regulation of late-phase allergic responses.

The CCL7-CCL2-CCR2 axis regulates IL-4 production in lungs and fungal immunity.

Expression of the chemokine receptor CCR2 can be detrimental or beneficial for infection resolution. Herein, we examined whether CCR2 was requisite for control of infection by the dimorphic fungus Histoplasma capsulatum. H. capsulatum-infected CCR2(-/-) mice manifested defects in inflammatory cell recruitment, increased IL-4, and progressive infection. Increased IL-4 in CCR2(-/-) mice primarily contributed to decreased host resistance as demonstrated by the ability of IL-4-neutralized CCR2(-/-) mice to resolve infection without altering inflammatory cell recruitment. Surprisingly, numerous alveolar macrophages and dendritic cells contributed to IL-4 production in CCR2(-/-) mice. IL-4-mediated impairment of immunity in CCR2(-/-) mice was associated with increased arginase-1 and YM1 transcription and increased transferrin receptor expression by phagocytic cells. Immunity in mice lacking the CCR2 ligand CCL2 was not impaired despite decreased inflammatory cell recruitment. Neutralization of the CCR2 ligand CCL7 in CCL2(-/-) mice, but not wild type, resulted in increased IL-4 and fungal burden. Thus, CCL7 in combination with CCL2 limits IL-4 generation and exerts control of host resistance. Furthermore, increased phagocyte-derived IL-4 in CCR2(-/-) mice is associated with the presence of alternatively activated phagocytic cells.

Deficiency in CCR2 increases susceptibility of mice to infection with an intracellular pathogen, Francisella tularensis LVS, but does not impair development of protective immunity.

CCR2 is the major chemokine receptor that regulates appropriate trafficking of inflammatory monocytes, but the role of this chemokine receptor and its ligands during primary and secondary infection with intracellular infections remains incompletely understood. Here we used murine infection with the Live Vaccine Strain (LVS) of Francisella tularensis to evaluate the role of CCR2 during primary and secondary parenteral responses to this prototype intracellular bacterium. We find that mice deficient in CCR2 are highly compromised in their ability to survive intradermal infection with LVS, indicating the importance of this receptor during primary parenteral responses. Interestingly, this defect could not be readily attributed to the activities of the known murine CCR2 ligands MCP-1/CCL2, MCP-3/CCL7, or MCP-5/CCL12. Nonetheless, CCR2 knockout mice vaccinated by infection with low doses of LVS generated optimal T cell responses that controlled the intramacrophage replication of Francisella, and LVS-immune CCR2 knockout mice survived maximal lethal Francisella challenge. Thus, fully protective adaptive immune memory responses to this intracellular bacterium can be readily generated in the absence of CCR2.