Higher Levels Of CCL2 Research Articles

Acute Lymphoblastic Leukemia Blast Cells Stimulate the Autocrine Production of CCL2 and IL-8 in Bone Marrow Stromal Cells

The interactions of Acute Lymphoblastic Leukemia (ALL) blasts with bone marrow (BM) stromal cells have a positive impact on leukemia cell survival and resistance to chemotherapy. ALL stimulates BM stromal cells, which reciprocally promotes leukemia cell survival. To identify molecules critically involved in leukemia–microenvironment crosstalk, we performed gene expression profiling analyses of primary BM endothelial cells (BMEC) and BM mesenchymal stem cells (BMMSC) following stimulation by primary ALL cells. Leukemia stimulation of BM stromal cells upregulates the expression of several inflammatory chemokines, including CCL2 and IL-8/CXCL8. Secretion of these molecules was confirmed by ELISA assays of in vitro co-culture experiments and in BM plasma samples from pediatric ALL patients. Most primary ALL samples were found to express mRNA for CCR2 and CXCR1/CXCR2, which are the cognate receptors for CCL2 and IL-8, respectively. Primary ALL cells expressing at least one myeloid marker (CD13, CD15 or CD33) exhibited increased mRNA expression of CCR2 (p = 0.02). Leukemia cells from most patients express CCL2 and IL-8 chemokines (ELISA test) but at lower levels than that of BMEC and BMMSC. In vitro functional studies revealed that the proliferation, survival and migration of primary ALL cells co-cultured with BM stromal cells were not affected by addition of CCL2, IL-8 or of neutralizing antibodies to these chemokines. On the other hand, both chemokines were found to enhance BMEC and BMMSC survival in serum-free medium and to increase their proliferation in serum-starved conditions. Interestingly, CCL2 and IL-8 affected endothelial morphogenesis as shown in Matrigel assays. Since CCL2 and IL-8 have suppressive effects in normal hematopoiesis but do not seem to affect primary ALL cells, it is possible that these chemokines may contribute to the establishment of survival/proliferative selective advantage for ALL cells in the leukemic BM microenvironment. In addition, CCL2 and IL-8 seems indirectly to contribute to ALL cell survival by stimulating the supporting BM stromal cells. Finally, preliminary results showed that standard risk pediatric ALL patients with BM plasma levels below 577pg/ml have better survival rates than those with higher CCL2 levels (p = 0.08). In conclusion, this work suggests a significant role for the chemokines CCL2 and IL-8 in the leukemia/microenvironment crosstalk in human ALL, and suggests that these molecules may represent valuable targets for therapeutic intervention in this cancer. Supported by: CNPq, FAPESP.

High Levels of Donor CCL2/MCP-1 Predict Graft-Related Complications and Poor Graft Survival After Kidney-Pancreas Transplantation

In this study we analyzed the role of CCL2, a member of the chemokine family, in early graft damage. Using simultaneous kidney-pancreas transplantation (SPK) as a model, we showed that brain death significantly increases circulating CCL2 levels in humans. We found that in such situations, high donor CCL2 levels (measured before organ recovery and at the onset of cold preservation) correlate with increased postreperfusion release of CCL2 by both the graft and recipient throughout the week following transplantation (n = 28). In a retrospective study of 77 SPK recipients, we found a significant negative association between high donor levels of CCL2 and graft survival. Decreased survival in these patients is related to early posttransplant complications, including a higher incidence of pancreas thrombosis and delayed kidney function. Taken together our data indicate that high CCL2 levels in the donor serum predict both an increase in graft/recipient CCL2 production and poor graft survival. This suggests that the severity of the inflammatory response induced by brain death influences the posttransplant inflammatory response, independent of subsequent ischemia and reperfusion.

Characterization of a Spontaneous Mouse Retinal Pigment Epithelial Cell Line B6-RPE07

A spontaneously arising retinal pigment epithelial (RPE) cell line (B6-RPE07) was cloned from a primary culture of mouse RPE cells and maintained in culture for more than 18 months. Morphologic and functional properties of this cell line have been characterized. The morphology of the B6-RPE07 cells was examined by phase-contrast light microscopy, electron microscopy, and confocal microscopy. Barrier properties were measured by the flux of fluorescence from the apical to the basolateral compartment of culture chambers. The abilities of the cells to bind/phagocytose photoreceptor outer segments (POS) were determined by confocal microscopy, electron microscopy, and flow cytometry. Cytokine/chemokine secretion was measured by cytometric bead array. The expression of visual cycle proteins was determined by RT-PCR and Western blotting. In standard culture conditions, B6-RPE07 cells display cobblestone morphology. When cultured on three-dimensional (3D) collagen gel-coated membranes, B6-RPE07 cells exhibit a monolayer epithelial polarization with apical surface microvilli. Immunohistochemistry of B6-RPE07 cultures revealed a high expression of pan-cytokeratin. B6-RPE07 cells also expressed the retinal pigment epithelium-specific marker CRALBP, but not RPE65. Cell junction proteins ZO-1 and beta-catenin, but not claudin-1/3 or occludin-1, were observed in B6-RPE07 cells. B6-RPE07 cells are able to bind, phagocytose, and digest POS. Finally, B6-RPE07 cells produce high levels of IL-6 and CCL2. This is the first report of a mouse RPE cell line with morphology, phenotype, and function similar to those of in vivo mouse RPE cells. This cell line will be a valuable resource for future RPE studies, in particular for in vivo gene modification and transplantation studies.

CXCL10 ( ) and CCL2 ( ) chemokines in systemic sclerosis a longitudinal study

To measure serum levels of CXCL10 and CCL2 chemokines in patients with SSc, and relate the findings to clinical phenotype and disease progression. Serum CXCL10 and CCL2 were assayed in 72 consecutive newly diagnosed SSc patients and in 72 sex- and age-matched controls. In 37 SSc and 37 controls, serum CXCL10 and CCL2 were re-evaluated 5 yrs later. SSc at onset showed significantly higher CXCL10 serum levels than controls (216 +/- 126 vs 92 +/- 53 pg/ml; P < 0.0001), as well as CCL2 (388 +/- 172 vs 318 +/- 120 pg/ml; P = 0.01). CXCL10 was significantly increased in SSc with interstitial lung involvement or with kidney involvement (P = 0.01 and P = 0.02, respectively). A significant decrease of CXCL10 was observed from the baseline after 5 yrs in SSc (137 +/- 112 vs 270 +/- 122 pg/ml, respectively; P < 0.0001), while no significant change was observed for CCL2 (418 +/- 176 vs 405 +/- 164 pg/ml; P = NS); the CCL2/CXCL10 ratio significantly increased at the fifth year (1.7 +/- 0.8 vs 3.5 +/- 2.5; P < 0.0001). No significant variations were observed in controls from the basal to the 5-yr evaluation with regards to CXCL10, CCL2 or CCL2/CXCL10 ratio. Our study demonstrates high serum levels of CXCL10 (Th1) and CCL2 (Th2) chemokines in newly diagnosed SSc. High values of CXCL10 are associated with a more severe clinical phenotype (lung and kidney involvement). CXCL10 declined during the follow-up, while CCL2 remained unmodified, suggesting that the disease progresses from the early Th1 inflammatory condition to the advanced Th2-like stage.

Targeting CCR1 for the Treatment of Osteolytic Bone Disease in Multiple Myeloma.

Osteolytic bone disease (OBD) is a frequent complication of multiple myeloma (MM), affecting 70 to 80% of the patients. OBD is characterized by imbalanced bone remodeling, due to decreased osteoblast (OB) number and increased osteoclast (OC) formation and activity. MM cells secrete osteoclastogenic factors, such as receptor activator of nuclear factor kappa B ligand (RANKL) and CCL3. In turn, OC support MM cell proliferation and survival, thus promoting a positive feedback that exacerbates bone resorption. Chemokines modulate osteoclastogenesis and promote MM cell proliferation, in particular CCL3 and its receptor CCR1 play an important role in mediating OBD in MM. MLN3897 (Millennium Pharmaceuticals, Cambridge) is a novel small molecule specific antagonist of human CCR1 (IC50 0.8 nM). It has a favorable toxicity profile in healthy volunteers and is currently undergoing phase II clinical trials in rheumatoid arthritis and multiple sclerosis. Here we evaluate the effects of MLN3897 on OC function and activity, as well as OC-MM cell interactions. Our in vitro data demonstrates a dual mechanism of action for MLN3897: it inhibits osteoclastogenesis and also overcomes the protective effects conferred by OC on MM cells. Our data further shows inhibition of OC formation and function by 40 and 70%, respectively, following MLN3897 treatment. This is mediated via inhibition of the fusion process and is accompanied by downregulation of pERK and c-fos signaling. To analyze its effect on MM cells, we verified CCR1 and CCR5 expression levels on MM1.S (15% and 3.6%) and OPM1 (3.8 and 0.7%). Our data show that OC secrete high levels of CCL3 which triggers MM cell migration; and that MLN3897 abrogates these effects by inhibiting the PI3K/Akt pathway. Moreover, MLN3897 overcomes the proliferative advantage conferred by OC on MM cells, as demonstrated in INA6, MM1.S and MM patient derived primary cells. OC induced MM cell proliferation is mediated by adhesion and cytokine secretion, and MLN3897 abrogates both MM cell-to-OC adhesion and interleukin-6 (IL6) secretion by OC in a co-culture system, thereby resulting in decreased MM cell survival and proliferation. To confirm these in vitro results, in vivo studies in a SCID-hu mouse model are underway. Implanted SCID-Hu INA-6 bearing mice are treated with twice daily oral MLN3897 for 3 weeks. The evaluation of osteolytic lesions and OC, OB and endothelial cell number; and tumor burden will be presented. Our in vitro results therefore show novel biologic sequelae of CCL3 and its inhibition on both osteoclastogenesis and MM cell growth. Our in vivo experiments will further validate the role of CCR1 in a human BM microenvironment-MM model, providing the framework for clinical trials of MLN3897 for the treatment of OBD in MM.

MLN3897, a novel CCR1 inhibitor, impairs osteoclastogenesis and inhibits the interaction of multiple myeloma cells and osteoclasts

AbstractThe interaction between osteoclasts (OCs) and multiple myeloma (MM) cells plays a key role in the pathogenesis of MM-related osteolytic bone disease (OBD). MM cells promote OC formation and, in turn, OCs enhance MM cell proliferation. Chemokines are mediators of MM effects on bone and vice versa; in particular, CCL3 enhances OC formation and promotes MM cell migration and survival. Here, we characterize the effects of MLN3897, a novel specific antagonist of the chemokine receptor CCR1, on both OC formation and OC-MM cell interactions. MLN3897 demonstrates significant impairment of OC formation (by 40%) and function (by 70%), associated with decreased precursor cell multinucleation and down-regulation of c-fos signaling. OCs secrete high levels of CCL3, which triggers MM cell migration; conversely, MLN3897 abrogates its effects by inhibiting Akt signaling. Moreover, MM cell-to-OC adhesion was abrogated by MLN3897, thereby inhibiting MM cell survival and proliferation. Our results therefore show novel biologic sequelae of CCL3 and its inhibition in both osteoclastogenesis and MM cell growth, providing the preclinical rationale for clinical trials of MLN3897 to treat OBD in MM.

Tumor Necrosis Factor α As a New Target for Renal Cell Carcinoma: Two Sequential Phase II Trials of Infliximab at Standard and High Dose

Tumor necrosis factor alpha (TNF-alpha) may play a role in renal cell carcinoma (RCC). We performed two sequential phase II studies of infliximab, an anti-TNF-alpha monoclonal antibody, in patients with immunotherapy-resistant or refractory RCC. Patients progressing after cytokine therapy were treated with intravenous infliximab as follows: study 1 (19 patients), 5 mg/kg at weeks 0, 2, and 6, and then every 8 weeks; study 2 (18 patients), 10 mg/kg at weeks 0, 2, and 6, and then every 4 weeks. Treatment continued until disease progression (PD). Response was assessed according to Response Evaluation Criteria in Solid Tumors. Plasma levels of TNF-alpha, CCL2, and interleukin-6 (IL-6) were measured before and during treatment. TNF-alpha and its receptors were detected in malignant cells in RCC biopsies. In study 1, three patients (16%) achieved partial response (PR) and three patients (16%) achieved stable disease (SD). Median duration of response (PR + SD) was 7.7 months (range, 5.0 to 40.5+ months). In study 2, 11 patients (61%) achieved SD. Median duration of response was 6.2 months (range, 3.5 to 24+ months). One patient developed grade 3 hypersensitivity and another died as a result of pulmonary infection/sepsis. Enzyme-linked immunosorbent assay analysis of plasma revealed that higher levels of TNF-alpha at baseline and higher levels of CCL2 during treatment were associated with PD. There were also correlations between higher levels of TNF-alpha, IL-6, and CCL2 and poor survival (< 12 months). This is the first direct clinical evidence suggesting that TNF-alpha may be a therapeutic target in RCC. Plasma levels of TNF-alpha, IL-6, and CCL2 may have predictive and prognostic significance.

Recombined CC chemokine ligand 2 into B16 cells induces production of Th2-dominanted cytokines and inhibits melanoma metastasis

This study is aimed to verify whether CCL2 can induce Th2 polarization in vivo and subsequently inhibit tumor metastasis. B16 cells (a murine melanoma cell line) highly expressing CCL2 (CCL2-B16 cells) were obtained by transfection with recombinant plasmid CCL2-pcDNA3. Primary thymocytes were co-cultured with CCL2-B16 cells and STAT-6-mediated Th2 polarization was noticed after co-culture. Caudal vein injection of CCL2-B16 cells effectively inhibited pulmonary metastasis in C57BL/6 mice, but not in nude mice, indicating that T cells play a role in CCL2-induced inhibition of tumor metastasis. We found that high level of CCL2 up-regulated the expression of Th2-related cytokine (IL-4) in tumor microenvironment and increased CD4+, CD8+, and CD45RB+ cells in the peripheral blood and tumor tissues. We also demonstrated that inoculation of mice with CCL2-B16 cells prolonged mice survival time when they were reinjected with wildtype B16 cells, implying that CCL2 can activate immuno-memory in mice. It is concluded that high expression of CCL2 can induce Th2 polarization in tumor microenvironment and can effectively inhibit tumor metastasis, which casts new lights on the role of chemokines in reconstruction of immune surveillance in patients suffering from tumors.

Streptococcus suis Serotype 2, an Important Swine and Human Pathogen, Induces Strong Systemic and Cerebral Inflammatory Responses in a Mouse Model of Infection

Streptococcus suis, an important swine and human pathogen, causes septic shock and meningitis. The pathogenesis of both systemic and CNS infections caused by S. suis is poorly understood. A hematogenous model of infection in CD1 mice was developed to study the systemic release of cytokines during the septic shock phase and the proinflammatory events in the CNS associated with this pathogen. Using a liquid array system, high levels of systemic TNF-alpha, IL-6, IL-12, IFN-gamma, CCL2, CXCL1, and CCL5 were observed 24 h after infection and might be responsible for the sudden death of 20% of animals. Infected mice that survived the early sepsis later developed clinical signs of meningitis and exhibited lesions in the meninges and in numerous regions of the brain, such as the cortex, hippocampus, thalamus, hypothalamus, and corpus callosum. Bacterial Ags were found in association with microglia residing only in the affected zones. In situ hybridization combined with immunocytochemistry showed transcriptional activation of TLR2 and TLR3 as well as CD14, NF-kappaB, IL-1beta, CCL2, and TNF-alpha, mainly in myeloid cells located in affected cerebral structures. Early transcriptional activation of TLR2, CD14, and inflammatory cytokines in the choroid plexus and cells lining the brain endothelium suggests that these structures are potential entry sites for the bacteria into the CNS. Our data indicate an important role of the inflammatory response in the pathogenesis of S. suis infection in mice. This experimental model may be useful for studying the mechanisms underlying sepsis and meningitis during bacterial infection.

CD16+ monocytes produce IL-6, CCL2, and matrix metalloproteinase-9 upon interaction with CX3CL1-expressing endothelial cells

The CD16+ subset of peripheral blood monocytes (Mo) is expanded dramatically during inflammatory conditions including sepsis, HIV-1 infection, and cancer. CD16+ express high levels of CX3CR1, which mediates arrest onto CX3CL1-expressing endothelial cells (EC) under flow conditions. In contrast, attachment of CD16- Mo onto cytokine-activated EC is independent of CX3CL1. Here, we investigate the ability of CD16+ and CD16- Mo to produce proinflammatory cytokines upon interaction with CX3CL1-expressing HUVEC. We demonstrate that CD16+ but not CD16- Mo produce high levels of IL-6, CCL2, and matrix metalloproteinase (MMP)-9 when cocultured with TNF/IFN-gamma-activated HUVEC or nonactivated HUVEC expressing CX3CL1. Furthermore, supernatants from Mo cocultured with cytokine-activated HUVEC induce neuronal death in vitro. These results suggest that membrane-bound CX3CL1 stimulates production of IL-6, CCL2, and MMP-9 by CD16+ Mo, likely via engagement of CX3CR1. Thus, expansion of CD16+ Mo and their accumulation onto CX3CL1-expressing EC may result in recruitment of Mo and T cell subsets at sites of inflammation in response to CCL2, IL-6-induced cell activation and/or differentiation, and MMP-9-mediated vascular and tissue injury.

Multiplex Bead Immunoassay Analysis of Aqueous Humor Reveals Distinct Cytokine Profiles In Uveitis

To extensively characterize the complex network of cytokines present in uveitis aqueous humor (AqH), and the relationships between cytokines and the cellular infiltrate. AqH from noninflammatory control subjects and patients with idiopathic, Fuchs' heterochromic cyclitis (FHC), and herpes-viral or Behçet's uveitis were analyzed for IL-1beta, -2, -4, -5, -7, -8, -10, -12, -13, -15, TNFalpha, IFNgamma, CCL2 (MCP-1), CCL5 (RANTES), CCL11 (Eotaxin), TGFbeta2, and CXCL12 (SDF-1), using multiplex bead immunoassays. The cellular infiltrate was also determined for each sample. Idiopathic uveitis AqH, compared with noninflammatory controls, was characterized by high levels of IL-6, IL-8, CCL2 and IFNgamma, the levels of which correlated with each other. For IL-6 and IL-8 these levels were proportional to the number of neutrophils present. By contrast, the levels of both TGFbeta2 and CXCL12 decreased in idiopathic uveitis AqH with increasing inflammation. Cluster analysis showed a degree of segregation between noninflammatory and idiopathic uveitis AqH. Further examination using random forest analysis yielded a complete distinction between these two groups. The minimum cytokines required for this classification were IL-6, IL-8, CCL2, IL-13, TNFalpha, and IL-2. Application of multiplex bead immunoassays has allowed us to identify distinct patterns of cytokines that relate to both clinical disease and the cellular infiltrates present. Bioinformatics analysis allowed identification of cytokines that differentiate idiopathic uveitis from noninflammatory control AqH and are likely to be important for the pathogenesis of uveitis.

The expression of CCL2 by T lymphocytes of mammary tumor bearers: Role of tumor-derived factors

Tumor-associated chemokines, including CC chemokine ligand 2/monocyte chemoattractant protein-1 (CCL2), are thought to play many roles in cancer progression. Here we demonstrate the novel finding that during growth of the D1-7,12-dimethylbenzanthracene-3 mammary tumor in BALB/c mice, there is a dramatic up-regulation of CCL2 in splenic T cells at both the mRNA and protein levels upon stimulation. Of particular relevance is the finding that tumor-infiltrating T cells also produce high levels of CCL2. While a variety of tumor cell lines have been found to produce CCL2, we found no detectable levels of CCL2 protein in supernatants of the cultured mammary tumor cells. Investigation of the mechanisms involved in CCL2 induction showed that treatment of splenic T cells with the tumor-derived factors GM-CSF and phosphatidyl serine (PS) resulted in increased CCL2 production. This increased production may be involved in the downregulation of IFN-γ by the T cells of tumor-bearing mice previously reported in this model, as treatment of splenic T lymphocytes with CCL2 resulted in a decreased secretion of IFN-γ by those cells.

Role of Donor-Derived Monocyte Chemoattractant Protein-1 in Murine Islet Transplantation

Monocyte chemoattractant protein-1 (CCL2/MCP-1) is a proinflammatory chemokine produced by several cell types, including pancreatic islets. High levels of donor-derived CCL2 have been associated with poor islet allograft outcome in patients with type 1 diabetes; however, the causal relationship is unknown. The constitutive and inducible expression of chemokines and their receptors by pancreatic islets in vitro were investigated, specifically the role of donor-derived CCL2 in marginal mass murine islet transplantation. The results showed that inflammatory cytokine stimulation of islets induced de novo expression of CCL2, CCL5/RANTES, CXCL9/MIG, and CXCL10/IP-10 and increased expression of CXCL2/macrophage-inflammatory protein-2. CCL2 mRNA and protein were highly expressed within 2 d in cultures. Transplantation of islets with high levels of CCL2 into syngeneic recipients led to a significantly greater influx of CCR2(+) cells and higher expression of monocyte/macrophage-associated inflammatory cytokines compared with low CCL2-donor islets. The level of pretransplantation CCL2 inversely correlated (P < 0.0001) with isograft function. In contrast, in CCR2-/- recipients, this correlation was not present. A direct toxic effect of CCL2 on islets was excluded by assessing cell viability and insulin release in vitro. In conclusion, CCL2 secreted by islets plays an important role in the immediate islet graft function. Strategies to decrease islet-derived CCL2 release may increase the success of islet transplantation.

MUC1/sec-expressing tumors are rejected in vivo by a T cell-dependent mechanism and secrete high levels of CCL2.

MUC1/sec is a secreted form of the glycoprotein mucin 1 (MUC1). To characterize the role that MUC1 and MUC1/sec have in tumor progression, these genes were expressed in DA-3 mammary tumor cells. DA-3 cells and DA-3 cells expressing the transmembrane MUC1 gene (DA-3/TM) grow with similar kinetics in BALB/c mice. Surprisingly, DA-3 cells expressing and secreting MUC1/sec (DA-3/sec) fail to form tumors in vivo. The mechanism of rejection was evaluated using mice deficient in constituents of the immune system. All mice lacking IFN-gamma, NK, NKT, or macrophages formed DA-3/sec tumors that regressed shortly after implantation. However, progressively growing DA-3/sec tumors developed in mice devoid of T lymphocytes. The importance of T lymphocytes in the rejection of DA-3/sec tumors was further supported by detection of DA-3-specific CTL in mice challenged with the DA-3/sec tumor. Recruitment of appropriate APC and effector cells is an important first step in the tumor clearance. Indeed, DA-3/sec cells or cell supernatants recruited 3-4 times as many macrophages as DA-3/TM cells in vivo, suggesting that a secreted chemotactic product is produced from DA-3/sec cells. RNA and protein analysis of DA-3/sec cells revealed that several genes are up-regulated by MUC1/sec expression, including MCP-1 (CCL-2). These results suggest DA-3/sec cells are capable of recruiting immune cells, and that rejection of DA-3/sec tumors, although aided by cells of the innate immune response, is ultimately due to T cell-mediated events.

IFN-alpha beta released by Mycobacterium tuberculosis-infected human dendritic cells induces the expression of CXCL10: selective recruitment of NK and activated T cells.

We recently reported that dendritic cells (DC) infected with Mycobacterium tuberculosis (Mtb) produce Th1/IFN-gamma-inducing cytokines, IFN-alpha beta and IL-12. In the present article, we show that maturing Mtb-infected DC express high levels of CCR7 and they become responsive to its ligand CCL21. Conversely, CCR5 expression was rapidly lost from the cell surface following Mtb infection. High levels of CCL3 and CCL4 were produced within 8 h after infection, which is likely to account for the observed CCR5 down-modulation on Mtb-infected DC. In addition, Mtb infection stimulated the secretion of CXCL9 and CXCL10. Interestingly, the synthesis of CXCL10 was mainly dependent on the Mtb-induced production of IFN-alpha beta. Indeed, IFN-alpha beta neutralization down-regulated CXCL10 expression, whereas the expression of CXCL9 appeared to be unaffected. The chemotactic activity of the Mtb-infected DC supernatants was evaluated by migration assays using activated NK, CD4(+), and CD8(+) cells that expressed both CCR5 and CXCR3. Mtb-induced expression of CCL3, CCL4, CXCL9, and CXCL10 was involved in the stimulation of NK and T cell migration. In accordance with the data on the IFN-alpha beta-induced expression of CXCL10, neutralization of IFN-alpha beta significantly reduced the chemotactic activity of the supernatant from Mtb-infected DC. This indicates that IFN-alpha beta may modulate the immune response through the expression of CXCL10, which along with CXCL9, CCL3, and CCL4 participates in the recruitment and selective homing of activated/effector cells, which are known to accumulate at the site of Mtb infection and take part in the formation of the granulomas.

Differential Roles of CC Chemokine Ligand 2/Monocyte Chemotactic Protein-1 and CCR2 in the Development of T1 Immunity

CCR2 and its major ligand, chemokine ligand 2 (CCL2)/monocyte chemotactic protein-1, have been found to influence T1/T2 immune response polarization. Our objective was to directly compare the roles of CCR2 and CCL2 in T1/T2 immune response polarization using a model of pulmonary Cryptococcus neoformans infection. Either deletion of CCR2 or treatment of wild-type mice with CCL2 neutralizing Ab produced significant and comparable reductions in macrophage and T cell recruitment into the lungs following infection. Both CCL2 neutralization and CCR2 deficiency resulted in significantly diminished IFN-gamma production, and increased IL-4 and IL-5 production by lung leukocytes (T1 to T2 switch), but only CCR2 deficiency promoted pulmonary eotaxin production and eosinophilia. In the lung-associated lymph nodes (LALN), CCL2-neutralized mice developed Ag-specific IFN-gamma-producing cells, while CCR2 knockout mice did not. LALN from CCR2 knockout mice also had fewer MHCII(+)CD11c(+) and MHCII(+)CD11b(+) cells, and produced significantly less IL-12p70 and TNF-alpha when stimulated with heat-killed yeast than LALN from wild-type or CCL2-neutralized mice, consistent with a defect in APC trafficking in CCR2 knockout mice. Neutralization of CCL2 in CCR2 knockout mice did not alter immune response development, demonstrating that the high levels of CCL2 in these mice did not play a role in T2 polarization. Therefore, CCR2 (but not CCL2) is required for afferent T1 development in the lymph nodes. In the absence of CCL2, T1 cells polarize in the LALN, but do not traffic from the lymph nodes to the lungs, resulting in a pulmonary T2 response.