Cigarette smoke-induced pulmonary inflammation, but not airway remodelling, is attenuated in chemokine receptor 5-deficient mice.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is characterized by a chronic inflammatory response of the airways and lungs to noxious particles and gases, mostly cigarette smoke (CS). Pathological changes characteristic of COPD include airway wall thickening, peribronchial fibrosis, peribronchial lymphoid follicles and destruction of lung parenchyma (emphysema). The recruitment of inflammatory cells into the lung in response to CS is thought to play an important role in the development of COPD. OBJECTIVE: Our aim was to study the contribution of chemokine receptor 5 (CCR5) to the pathogenesis of COPD and specifically whether the development of airway remodelling is a direct result of airway inflammation or rather occurs through an independent mechanism. METHODS: In this study, C57BL/6 wild-type mice and CCR5-deficient mice were subjected to sub-acute (4 weeks) and chronic (24 weeks) CS exposure. RESULTS: Both sub-acute and chronic CS exposure significantly increased CCR5 mRNA expression and protein levels of CCR5 ligands [macrophage inflammatory protein-1alpha (MIP-1alpha), MIP-1beta and regulated upon activation, normal T expressed and secreted (RANTES)], and induced the recruitment of neutrophils, macrophages, dendritic cells, and lymphocytes to the bronchoalveolar lavage (BAL) of wild-type mice. Chronic CS exposure also increased the number and extent of peribronchial lymphoid follicles. In CCR5 knockout (KO) mice, these CS-induced increases in CCR5 ligands, inflammatory cells in BAL and peribronchial lymphoid follicles were all significantly attenuated compared with wild-type animals. Importantly, chronic CS exposure induced airspace enlargement in wild-type mice, while CCR5 KO mice were partially protected against the development of emphysema. However, CCR5 deficiency did not affect CS-induced airway wall remodelling, because chronic CS exposure induced a similar increase in airway wall thickness, smooth muscle mass and peribronchial deposition of collagen and fibronectin in both wild-type and CCR5 KO mice. CONCLUSION: Our data suggest that CCR5 contributes to pulmonary inflammation and to the development of emphysema in response to CS. CCR5 is, however, not implicated in CS-induced airway wall remodelling, suggesting that the mechanisms that lead to airway inflammation are distinct to those responsible for airway remodelling.

CCL2-independent role of CCR2 in immune responses against Leishmania major.

The chemokine CCL2 (MCP-1) and its receptor CCR2 modulate leucocyte migration and T helper differentiation. CCL2 or CCR2 knockout (KO) mice have divergent phenotypes following infection with the intracellular parasite Leishmania major (L. major). Compared to wild-type (WT) mice, intradermally infected CCR2 KO mice in the L. major-resistant C57BL/6j background become susceptible and fail to generate protective Th1 responses. In contrast, subcutaneously infected CCL2 KO mice in the L. major-susceptible BALB/c background are resistant and exhibit reduced pathogenic Th2 responses. Here we explore two variables that may account for this contrasting outcome, namely background strain and route of infection. We found that the CCR2-null state, both in the BALB/c and the C57BL/6j background, was associated with increased susceptibility to intradermal or subcutaneous L. major infection. Notably, the CCL2-null state did not change the ability of C57BL/6j mice to mount protective responses following intradermal infection. Dual genetic inactivation of CCR2 and CCL2 in the L. major-resistant C57BL/6j background resulted in a shift to a susceptible phenotype analogous to that of CCR2 KO in the C57BL/6j background. We concluded that CCL2-independent effects of CCR2 are indispensable for the control of L. major infection and the generation of protective immune responses.

The chemokine receptor CCR2 mediates the binding and internalization of monocyte chemoattractant protein-1 along brain microvessels.

Previous results from this laboratory revealed the presence of high-affinity saturable binding sites for monocyte chemoattractant protein-1 (MCP-1) along human brain microvessels (Andjelkovic et al., 1999; Andjelkovic and Pachter, 2000), which suggested that CC chemokine receptor 2 (CCR2), the recognized receptor for this chemokine, was expressed by the brain microvascular endothelium. To test the role of CCR2 directly in mediating MCP-1 interactions with the brain microvasculature, we assessed MCP-1 binding activity in murine brain microvessels isolated from wild-type mice and from CCR2 (-/-) mice engineered to lack this receptor. Results demonstrate that MCP-1 binding is greatly attenuated in microvessels prepared from CCR2 (-/-) mice compared with wild-type controls. Moreover, microvessels from wild-type mice exhibited MCP-1-induced downmodulation in MCP-1 binding and a recovery of binding activity that was not dependent on de novo protein synthesis. Furthermore, MCP-1 was shown to be internalized within wild-type microvessels, but not within microvessels obtained from CCR2 (-/-) mice, additionally demonstrating that CCR2 is obligatory for MCP-1 endocytosis. Last, internalization of MCP-1, but not transferrin, was observed to be inhibited by disruption of caveolae. Internalized MCP-1 also colocalized at some sites with caveolin-1, a major protein of caveolae, implying that this chemokine is endocytosed, in part, via nonclathrin-coated vesicles. These results prompt consideration that MCP-1 signals may be relayed across the blood-brain barrier by highly specialized interactions of this chemokine with its cognate receptor, CCR2, along brain microvascular endothelial cells.

Macrophage inflammatory protein-1alpha uses a novel receptor for primitive hemopoietic cell inhibition.

Macrophage inflammatory protein-1alpha (MIP-1alpha) is a member of the chemokine family of proinflammatory mediators. In addition to its inflammatory roles, MIP-1alpha has been shown to be active as an inhibitor of primitive hemopoietic cell proliferation. Indeed, a dysfunction in this inhibitory process has been postulated to contribute to leukemogenesis. Research has been aimed at characterizing the receptor involved in cellular inhibition by MIP-1alpha. This study demonstrates that of all the beta-chemokines tested, only MIP-1alpha is capable of inhibiting primitive hemopoietic cell proliferation. Because no MIP-1alpha-specific receptors have been identified, this suggests that inhibition is mediated by an uncharacterized receptor. Further evidence for the involvement of a novel receptor in this process is the equivalent potencies of MIP-1alphaS and MIP-1alphaP variants of human MIP-1alpha and the fact that primitive cells from bone marrow derived from individual MIP-1alpha receptor null mice display a full response to MIP-1alpha inhibition.

Protection from pulmonary fibrosis in the absence of CCR2 signaling.

Pulmonary fibrosis can be modeled in animals by intratracheal instillation of FITC, which results in acute lung injury, inflammation, and extracellular matrix deposition. We have previously shown that despite chronic inflammation, this model of pulmonary fibrosis is lymphocyte independent. The CC chemokine monocyte-chemoattractant protein-1 is induced following FITC deposition. Therefore, we have investigated the contribution of the main monocyte-chemoattractant protein-1 chemokine receptor, CCR2, to the fibrotic disease process. We demonstrate that CCR2(-/-) mice are protected from fibrosis in both the FITC and bleomycin pulmonary fibrosis models. The protection is specific for the absence of CCR2, as CCR5(-/-) mice are not protected. The protection is not explained by differences in acute lung injury, or the magnitude or composition of inflammatory cells. FITC-treated CCR2(-/-) mice display differential patterns of cellular activation as evidenced by the altered production of cytokines and growth factors following FITC inoculation compared with wild-type controls. CCR2(-/-) mice have increased levels of GM-CSF and reduced levels of TNF-alpha compared with FITC-treated CCR2(+/+) mice. Thus, CCR2 signaling promotes a profibrotic cytokine cascade following FITC administration.

Lack of CCR2 results in increased mortality and impaired leukocyte activation and trafficking following infection of the central nervous system with a neurotropic coronavirus.

In the present study, we evaluated the role of CCR2 in a model of viral-induced neurologic disease. An orchestrated expression of chemokines, including the CCR2 ligands monocyte chemoattractant protein-1/CCL2 and monocyte chemoattractant protein-3/CCL7, occurs within the CNS following infection with mouse hepatitis virus (MHV). Infection of mice lacking CCR2 (CCR2(-/-)) with MHV resulted in increased mortality and enhanced viral recovery from the brain that correlated with reduced (p < or = 0.04) T cell and macrophage/microglial (determined by F4/80 Ag expression, p < or = 0.004) infiltration into the CNS. Moreover, MHV-infected CCR2(-/-) mice displayed a significant decrease in Th1-associated factors IFN-gamma (p < or = 0.001) and RANTES/CCL5 (p < or = 0.002) within the CNS as compared with CCR2(+/+) mice. Further, peripheral CD4(+) and CD8(+) T cells from immunized CCR2(-/-) mice displayed a marked reduction in IFN-gamma production in response to viral Ag and did not migrate into the CNS of MHV-infected recombination-activating gene (RAG)1(-/-) mice following adoptive transfer. In addition, macrophage/microglial infiltration into the CNS of RAG1(-/-) mice receiving CCR2(-/-) splenocytes was reduced (p < or = 0.05), which correlated with a reduction in the severity of demyelination (p < or = 0.001) as compared with RAG1(-/-) mice receiving splenocytes from CCR2(+/+) mice. Collectively, these results indicate an important role for CCR2 in host defense and disease by regulating leukocyte activation and trafficking.

Reduced macrophage infiltration and demyelination in mice lacking the chemokine receptor CCR5 following infection with a neurotropic coronavirus.

Studies were performed to investigate the contributions of the CC chemokine receptor CCR5 in host defense and disease development following intracranial infection with mouse hepatitis virus (MHV). T cell recruitment was impaired in MHV-infected CCR5(-/-) mice at day 7 postinfection (pi), which correlated with increased (P < or = 0.03) titers within the brain. However, by day 12 pi, T cell infiltration into the CNS of infected CCR5(-/-) and CCR5(+/+) mice was similar and both strains exhibited comparable viral titers, indicating that CCR5 expression is not essential for host defense. Following MHV infection of CCR5(+/+) mice, greater than 50% of cells expressing CCR5 antigen were activated macrophage/microglia (determined by F4/80 antigen expression). In addition, infected CCR5(-/-) mice exhibited reduced (P < or = 0.02) macrophage (CD45(high)F4/80(+)) infiltration, which correlated with a significant reduction (P < or = 0.001) in the severity of demyelination compared to CCR5(+/+) mice. These data indicate that CCR5 contributes to MHV-induced demyelination by allowing macrophages to traffic into the CNS.

Enhanced airway Th2 response after allergen challenge in mice deficient in CC chemokine receptor-2 (CCR2).

To evaluate the role of CCR2 in allergic asthma, mutant mice deficient in CCR2 (CCR2(-/-)) and intact mice were sensitized with i.p. OVA with alum on days 0 and 7, and challenged by inhalation with nebulization of either OVA or saline. Airway hyperreactivity, measured by the methacholine-provoked increase in enhanced pause, was significantly increased (p < 0.05) in OVA-challenged CCR2(-/-) mutant mice, compared with comparably challenged CCR2(+/+) mice. OVA-challenged CCR2(-/-) mutants also were also found to have enhanced bronchoalveolar lavage fluid eosinophilia, peribronchiolar cellular cuffing, and Ig subclass switching, with increase in OVA-specific IgG(1) and IgE. In addition, RNase protection assay revealed increased whole lung expression of IL-13 in OVA-challenged CCR2(-/-) mutants. Unexpectedly, serum monocyte chemotactic protein-1 levels were 8-fold higher in CCR2(-/-) mutants than in CCR2(+/+) mice sensitized to OVA, but OVA challenge had no additional effect on circulating monocyte chemotactic protein-1 in either genotype. Ag stimulation of lymphocytes isolated from OVA-sensitized CCR2 mutants revealed a significant increase (p < 0.05) in IL-5 production, which differed from OVA-stimulated lymphocytes from sensitized CCR2(+/+) mice. These experiments demonstrate an enhanced response in airway reactivity and in lung inflammation in CCR2(-/-) mutant mice compared with comparably sensitized and challenged CCR2(+/+) mice. These observations suggest that CC chemokines and their receptors are involved in immunomodulation of atopic asthma.

RANTES promotes growth and survival of human first-trimester forebrain astrocytes.

We have examined the role of alpha and beta chemokines in the promotion of the ontogenetic development of the brain. RANTES was expressed preferentially in human fetal astrocytes in an age-dependent manner. Astrocytes from 5-week-old brains showed high proliferation and reduced survival, whereas 10-week-old astrocytes exhibited opposite effects. These effects were suppressed by anti-RANTES or anti-RANTES receptor antibodies and were enhanced by recombinant RANTES. RANTES induced tyrosine phosphorylation of several cellular proteins and nuclear translocation of STAT-1 in astrocytes. Interferon-gamma (IFN-gamma) was required for RANTES effects because RANTES induced IFN-gamma and only 10-week-old astrocytes expressed the IFN-gamma receptor. Blocking of IFN-gamma with antibody reversed the effects of RANTES, indicating that cytokine/chemokine networks are critically involved in brain development.

Inducible expression of inflammatory chemokines in respiratory syncytial virus-infected mice: role of MIP-1alpha in lung pathology.

Lower respiratory tract disease caused by respiratory syncytial virus (RSV) is characterized by profound airway mucosa inflammation, both in infants with naturally acquired infection and in experimentally inoculated animal models. Chemokines are central regulatory molecules in inflammatory, immune, and infectious processes of the lung. In this study, we demonstrate that intranasal infection of BALB/c mice with RSV A results in inducible expression of lung chemokines belonging to the CXC (MIP-2 and IP-10), CC (RANTES, eotaxin, MIP-1beta, MIP-1alpha, MCP-1, TCA-3) and C (lymphotactin) families. Chemokine mRNA expression occurred as early as 24 h following inoculation and persisted for at least 5 days in mice inoculated with the highest dose of virus (10(7) PFU). In general, levels of chemokine mRNA and protein were dependent on the dose of RSV inoculum and paralleled the intensity of lung cellular inflammation. Immunohisthochemical studies indicated that RSV-induced expression of MIP-1alpha, one of the most abundantly expressed chemokines, was primarily localized in epithelial cells of the alveoli and bronchioles, as well as in adjoining capillary endothelium. Genetically altered mice with a selective deletion of the MIP-1alpha gene (-/- mice) demonstrated a significant reduction in lung inflammation following RSV infection, compared to control littermates (+/+ mice). Despite the paucity of infiltrating cells, the peak RSV titer in the lung of -/- mice was not significantly different from that observed in +/+ mice. These results provide the first direct evidence that RSV infection may induce lung inflammation via the early production of inflammatory chemokines.

A study on the density and distribution of uterine Natural Killer cells at mid pregnancy in mice genetically-ablated for CCR2, CCR 5 and the CCR5 receptor ligand, MIP-1 alpha.

Several chemoattractants mediate Natural Killer (NK) cell migration. The CC-chemokines, monocyte inflammatory protein (MIP)-1 alpha, regulated upon activation, normal T cell expressed and secreted (RANTES) and macrophage chemotactic protein (MCP)-1 are the most potent. Peripheral NK cells express the CC-chemokine receptor CCR2, for MCP-1 and CCR5, for MIP-1 alpha and RANTES. These chemokines are detected in the uterus during the estrous cycle and become elevated during pregnancy. To assess the roles of CCR2, CCR5 and MIP-1 alpha in NK cell migration to the uterus and localization within implantation sites, histological analysis was conducted on implantation sites from mice genetically-ablated for CCR2, CCR5, MIP-1 alpha or CCR2 and MIP-1 alpha. Uterine NK (uNK) cell densities in both the decidua basalis and mesometrial lymphoid aggregate of pregnancy (MLAp) of all mutant strains matched wildtype controls. Ratios of vascular: non-vascular uNK cell position were identical in mutants and controls. In the decidua basalis, 25-35% and in the MLAp, 15-20% of uNK cells were perivascular. Intravascular uNK cells were observed in the decidua basalis but not in the MLAp and were more numerous at gestation day 10 than 12. Two measures of uNK cell activation, cell diameter and cytoplasmic granule number, were similar in the mutants and controls. Thus, migration, distribution and activation of NK cells within the pregnant uterus are independent of CCR2, CCR5 and MIP-1 alpha.

The chemokine receptor CCR2 is involved in macrophage recruitment to the injured peripheral nervous system.

Wallerian degeneration is one of the most elementary reactions of the nervous system after transection of axons, leading to the recruitment of mononuclear cells from the systemic circulation. However, the exact mechanisms regulating this cell invasion have not yet been clarified in detail. Chemokines and their receptors play a central role in leukocyte trafficking, in particular the chemokine MCP-1 has been strongly implicated in macrophage recruitment to the injured nervous system. The present study investigates the course of Wallerian degeneration after transection of the sciatic nerve in mice deficient in two chemokine receptors: CCR2, the main receptor for MCP-1, and CCR5, a marker for Th1 T lymphocytes but also present on macrophages. The number of invading macrophages was determined by immunocytochemistry for three typical macrophage antigens (F4/80, Mac-1, LFA-1). The chemokine receptor CCR2 was expressed by infiltrating cells in the transected nerve stumps. Macrophage invasion was significantly impaired in CCR2-knockout mice when compared with wildtype controls and CCR5-deficient mice. Subsequently, there was a corresponding decrease in myelin phagocytosis due to the reduced invasion of phagocytic macrophages. These data demonstrate the involvement of the chemokine receptor CCR2 in macrophage recruitment to the injured nervous system.

CC chemokine receptor 2 is required for macrophage infiltration and vascular hypertrophy in angiotensin II-induced hypertension.

Recent studies have identified the presence of macrophages in the arterial wall of hypertensive animals and suggested that as is the case in atherosclerosis, macrophage products may be important mediators of the adaptive response of the arterial wall. In support of this, we have previously shown that the expression of monocyte chemoattractant protein-1 is upregulated in the arteries of hypertensive animals. We hypothesized that macrophage recruitment is a critical step in the pathogenesis of hypertension. To obtain insights into this potential mechanism, we made use of mice deficient in the CC chemokine receptor 2 (CCR2), the receptor for monocyte chemoattractant protein-1. Hypertension was induced with the subcutaneous administration of angiotensin II (0.75 mg. kg(-1). d(-1)) for 7 days. Using in situ hybridization with a probe for c-fms to identify macrophages, we found that hypertension-induced macrophage infiltration of the arterial wall was virtually eliminated in CCR2-deficient mice. In addition, vascular hypertrophy was reduced by approximately 65% compared with wild-type animals. These data demonstrate that CCR2 is essential for the recruitment of macrophages into the arterial wall in the setting of hypertension. Furthermore, the decreased hypertrophic response suggests that vascular hypertrophy occurs in part as a consequence of macrophage infiltration. In angiotensin II-induced hypertension, CCR2-mediated responses are critical to the process of macrophage recruitment and vascular hypertrophy and may represent one mechanism by which at least some forms of hypertension may lead to the development of atherosclerosis.

CC chemokine receptor 2 is critical for induction of experimental autoimmune encephalomyelitis.

Experimental autoimmune encephalomyelitis (EAE) is a CD4(+) T lymphocyte-mediated disease of the central nervous system (CNS) characterized by mononuclear cell infiltration, demyelination, and paralysis. We previously demonstrated a role for chemokines in acute and relapsing EAE pathogenesis. Presently, we investigated the role of CC chemokine receptor 2 (CCR2) in acute EAE. CCR2(-/-) mice did not develop clinical EAE or CNS histopathology, and showed a significant reduction in T cell- and CNS-infiltrating CD45(high)F4/80(+) monocyte subpopulations. Peripheral lymphocytes from CCR2(-/-) mice produced comparable levels of interferon-gamma (IFN-gamma) and interleukin (IL)-2 in response to antigen-specific restimulation when compared with control mice. Adoptively transferred myelin oligodendrocyte glycoprotein 35-55-specific T cells lacking expression of CCR2 were able to induce EAE, whereas CCR2(-/-) recipients of wild-type T cells failed to develop disease. These results suggest that CCR2 expression on host-derived mononuclear cells is critical for disease induction.

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

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

Contrasting effects of CCR5 and CCR2 deficiency in the pulmonary inflammatory response to influenza A virus.

The immune response to influenza A virus is characterized by an influx of both macrophages and T lymphocytes into the lungs of the infected host, accompanied by induced expression of a number of CC chemokines. CC chemokine receptors CCR5 and CCR2 are both expressed on activated macrophages and T cells. We examined how the absence of these chemokine receptors would affect pulmonary chemokine expression and induced leukocyte recruitment by infecting CCR5-deficient mice and CCR2-deficient mice with a mouse-adapted strain of influenza A virus. CCR5(-/-) mice displayed increased mortality rates associated with acute, severe pneumonitis, whereas CCR2(-/-) mice were protected from the early pathological manifestations of influenza because of defective macrophage recruitment. This delay in macrophage accumulation in CCR2(-/-) mice caused a subsequent delay in T cell migration, which correlated with high pulmonary viral titers at early time points. Infected CCR5(-/-) mice and CCR2(-/-) mice both exhibited increased expression of the gene for MCP-1, the major ligand for CCR2(-/-) and a key regulator of induced macrophage migration. These studies illustrate the very different roles that CCR5 and CCR2 play in the macrophage response to influenza infection and demonstrate how defects in macrophage recruitment affect the normal development of the cell-mediated immune response.

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.

Induction of experimental autoimmune encephalomyelitis in C57BL/6 mice deficient in either the chemokine macrophage inflammatory protein-1alpha or its CCR5 receptor.

Macrophage inflammatory protein (MIP)-1alpha is a chemokine that is associated with Th1 cytokine responses. Expression and antibody blocking studies have implicated MIP-1alpha in multiple sclerosis (MS) and in experimental autoimmune encephalomyelitis (EAE). We examined the role of MIP-1alpha and its CCR5 receptor in the induction of EAE by immunizing C57BL / 6 mice deficient in either MIP-1alpha or CCR5 with myelin oligodendrocyte glycoprotein (MOG). We found that MIP-1alpha-deficient mice were fully susceptible to MOG-induced EAE. These knockout animals were indistinguishable from wild-type mice in Th1 cytokine gene expression, the kinetics and severity of disease, and infiltration of the central nervous system by lymphocytes, macrophages and granulocytes. RNase protection assays showed comparable accumulation of mRNA for the chemokines interferon-inducible protein-10, RANTES, macrophage chemoattractant protein-1, MIP-1beta, MIP-2, lymphotactin and T cell activation gene-3 during the course of the disease. CCR5-deficient mice were also susceptible to disease induction by MOG. The dispensability of MIP-1alpha and CCR5 for MOG-induced EAE in C57BL / 6 mice supports the idea that differential chemokine expression patterns represent differences in disease mechanism that underlie various models of EAE, and possibly distinct patterns of pathology seen in MS.

CCR2 expression determines T1 versus T2 polarization during pulmonary Cryptococcus neoformans infection.

Pulmonary clearance of the encapsulated yeast Cryptococcus neoformans requires the development of T1-type immunity. The objective of this study was to determine the role of CCR2 in leukocyte recruitment and development of T1-type cell-mediated immunity during pulmonary C. neoformans infection. Intratracheal inoculation of C. neoformans into CCR2 knockout (CCR2-/-) mice produced a prolonged pulmonary infection (5000-fold CFU at 6 wk compared with CCR2+/+ mice) and significant dissemination to the spleen and brain (160- and 800-fold greater). In addition, CCR2 deficiency resulted in significantly reduced recruitment of macrophages (weeks 1-3) and CD8+ T cells (weeks 1-2) into the lungs. The immune response in CCR2-/- mice was characterized by chronic pulmonary eosinophilia, crystal deposition in the lungs, pulmonary leukocyte production of IL-4 and IL-5 but not IFN-gamma, lack of anticryptococcal delayed-type hypersensitivity, and high levels of serum IgE. These results demonstrate that expression of CCR2 is required for the development of a T1-type response to C. neoformans infection and lack of CCR2 results in a switch to a T2-type response. Thus, CCR2 plays a critical role in promoting the development of T1- over T2-type immune responses in the lung following cryptococcus infection.

Defects in the generation of IFN-gamma are overcome to control infection with Leishmania donovani in CC chemokine receptor (CCR) 5-, macrophage inflammatory protein-1 alpha-, or CCR2-deficient mice.

We investigated the immune responses in mice lacking CCR2, CCR5, or macrophage inflammatory protein-1 alpha (MIP-1 alpha), a ligand for CCR5, in two situations: following T cell stimulation or after challenge with Leishmania donovani, an intracellular microbe whose control is dependent on a Th1 immune response. Mice deficient in CCR5, MIP-1 alpha, or CCR2 had reduced IFN-gamma responses following ligation of the TCR. Reduced IFN-gamma responses following PMA and ionomycin were also observed in CD8+ T cells of CCR5-/- and CCR2-/- mice. During the early phases of infection, all three knockout mice had low Ag-specific IFN-gamma responses. However, this reduced IFN-gamma response was overcome during a state of persistent Ag stimulation (chronic infection), and was not associated with an adverse parasitologic outcome in any of the gene-targeted mouse strains. To the contrary, during the late phase of infection, an exaggerated Ag-specific IFN-gamma response was evident in CCR5-/- and MIP-1 alpha-/- mice, and this correlated with an enhanced control of parasite replication. Although granuloma formation was abnormal in each of the knockout mice, there was no correlation between the number or architecture of the granulomas and parasite burden. Collectively, these findings indicate an important role for CCR5, MIP-1 alpha, and CCR2 in granulomatous inflammation, and that CCR5 and MIP-1 alpha, possibly acting through CCR5, might play a deleterious role in the outcome of chronic L. donovani infection. Our data also suggest that there might be cross-talk between TCR and chemokine receptor signaling pathways.