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Granulomas are innate sequestration responses that can be modified by superimposed acquired immune mechanisms. The present study examined the innate stage of pulmonary granuloma responses to bead-immobilized Th1- and Th2-inducing pathogen antigens (Ags), Mycobacteria bovis purified protein derivative (PPD) and Schistosoma mansoni soluble egg Ags (SEA). Compared to a nonpathogen Ag, PPD and SEA bead elicited larger lesions with the former showing accelerated inflammation. Temporal analyses of cytokine and chemokine transcripts showed all Ag beads induced tumor necrosis factor-alpha mRNA but indicated biased interleukin (IL)-1, IL-6, and IL-12 expression with PPD challenge. All beads elicited comparable levels of CXCL9, CXL10, CCL2, CCL17, and CCL22 mRNA, but PPD beads caused biased CXCL2 CXCL5, CCL3, and CCL4 expression whereas both pathogen Ags induced CCL7. Immunohistochemical, electron microscopic, and flow cytometric analyses showed that Ag beads mobilized CD11c+ dendritic cells (DCs) of comparable maturation. Transfer of DCs from PPD Ag-challenged lungs conferred a Th1 anamnestic cytokine response in recipients. Surprisingly, transfer of DCs from the helminth SEA-challenged lungs did not confer the expected Th2 response, but instead rendered recipients incapable of Ag-elicited IL-4 production. These results provide in vivo evidence that lung DCs recruited under inflammatory conditions favor Th1 responses and alternative mechanisms are required for Th2 commitment.

Type-1 and type-2 lung granulomas, respectively, elicited by bead immobilized Mycobacteria bovis and Schistosoma mansoni egg antigens (Ags) display different patterns of chemokine expression. This study tested the hypothesis that chemokine expression patterns were related to upstream cytokine signaling. Using quantitative transcript analysis, we defined expression profiles for 16 chemokines and then examined the in vivo effects of neutralizing antibodies against interferon-gamma (IFN-gamma), interleukin (IL)-4, IL-10, IL-12, and IL-13. Transcripts for CXCL2, -5, -9, -10, and -11 and the CCL chemokine, CCL3, and lymphotactin (XCL1), were largely enhanced by Th1-related cytokines, IFN-gamma or IL-12. Transcripts for CCL11, CCL22, CCL17, and CCL1 were enhanced largely by Th2-related cytokines, IL-4, IL-10, or IL-13. Transcripts for CCL4, CCL2, CCL8, CCL7, and CCL12 were potentially induced by either Th1- or Th2-related cytokines, although some of these showed biased expression. IFN-gamma and IL-4 enhanced the greatest complement of transcripts, and their neutralization had the greatest anti-inflammatory effect on type-1 and type-2 granulomas, respectively. Th1/Th2 cross-regulation was evident because endogenous Th2 cytokines inhibited type-1, whereas Th1 cytokines inhibited type-2 biased chemokines. These findings reveal a complex cytokine-chemokine regulatory network that dictates profiles of local chemokine expression during T cell-mediated granuloma formation.

Host immune systems have evolved specialized responses to multicellular parasites. This is well represented by the type 2 granulomatous response to Schistosoma mansoni egg antigens, which is an eosinophil-rich inflammatory response mediated by Th2-associated cytokines. Using Ag-bead models of pulmonary granuloma formation in mice, we defined characteristic chemokine (CK) profiles in the granulomatous lungs. Our findings point to a role for C-C chemokine receptor-2 (CCR2) and CCR3 agonists such as monocyte chemotactic proteins (MCPs) 1/CCL2, 3/CCL7 and 5/CCL12 as important participants that are subject to regulation by Th2 cytokines interleukin (IL)-4 and IL-13. CCR4 and CCR8 agonists are also likely contributors. Analysis of CK receptor knockout mice revealed that CCR2 ligands (e.g. MCP-1 and 5) promoted early phase granuloma macrophage accumulation, whereas anti-MCP-3 (CCL7) antibody treatment abrogated eosinophil recruitment. CCR8 knockout mice also demonstrated impaired eosinophil recruitment but this appeared to be related to impaired Th2 cell function. Transcript analysis of CD4+ T cells generated during schistosome granuloma formation failed to show biased CCR8 expression but, having a more limited receptor repertoire, these cells were likely more dependent on CCR8 ligands. Together, these studies indicate an intricate involvement of chemokines in various stages and aspects of schistosomal egg Ag-elicited granuloma formation.

Cytokine and chemokine responses during anamnestic type-1 and type-2 lung granuloma formation were evaluated in mice at 6,12,18 and 24-months of age. Lesions were induced by embolizing Sepharose beads coupled to Mycobacterium bovis purified protein derivative or soluble Schistosoma mansoni egg antigens. Type-1 inflammation was reduced by 18 months, whereas type-2 granulomas not until 24 months of age. In type-1 draining lymph nodes cultures, interferon-gamma (IFNgamma) declined to a nadir by 18, and then partly recovered at 24 months. In contrast, IL-4 was not significantly impaired in type-2 cultures until 24 months. Type-1 and 2 node cultures also displayed decreased IL-13, but paradoxically enhanced IL-5 production at 24 months. Chemokine transcripts in granulomatous lungs displayed age-related alterations. In the type-1 response, CXCL9 (monokine-induced by IFNgamma) declined with age then partly recovered at 24 months parallelling lymph node IFNgamma levels. Transcripts for MIP-2/CXCL2, IP-10/CXCL10, MCP-1/CCL2, and MCP-5/CCL12 increased at 24 months. In the type-2 response MCP-1/CCL2, MCP-3/CCL7, MCP-5/CCL12 and TARC/CCL17 collapsed at 24 months paralleling local IL-4 transcript levels, yet some chemokine transcripts such as KC/CXCL1 and eotaxin/CCL11 were unaffected. These findings suggest that cytokine and chemokine responses degrade differentially with age shifting Th1/Th2 crossregulatory pressures and local expression of chemokines.

Chemokines and their G-protein-coupled receptors represent an ancient and complex system of cellular communication participating in growth, development, homeostasis and immunity. Chemokine production has been detected in virtually every microbial infection examined; however, the precise role of chemokines is still far from clear. In most cases they appear to promote host resistance by mobilizing leukocytes and activating immune functions that kill, expel, or sequester pathogens. In other cases, the chemokine system has been pirated by pathogens, especially protozoa and viruses, which have exploited host chemokine receptors as modes of cellular invasion or developed chemokine mimics and binding proteins that act as antagonists or inappropriate agonists. Understanding microbial mechanisms of chemokine evasion will potentially lead to novel antimicrobial and anti-inflammatory therapeutic agents.

Chemokines constitute a large family of chemotactic cytokines that belong to a super-gene family of 8-10 kDa proteins. The chemokines are considered to be primarily beneficial in host defense against invading pathogens. However, the reactions induced by chemokines can be occasionally excessive, resulting in a harmful response to the host. Recent studies in chemokine biology have elucidated that chemokines are involved in the initiation, development, and maintenance of numbers of diseases including lung diseases. In addition to its chemotactic activity, evidence suggests that chemokines can modify the outcome of the cell-mediated immune responses by altering the Th1/Th2 cytokine profile. Chemokines are also capable of dictating the direction of specific immune responses. Chemokine action is mediated by a large super-family of G-protein coupled receptors, and the receptors are preferentially expressed on Th1/Th2 cells. Certain chemokine receptors are constitutively expressed in immune surveying cells such as dendritic cells and naive T cells. The corresponding chemokines are present in normal lymphoid tissues, suggesting a role of chemokines/receptors in cell homing and cell-cell communication in lymphoid tissue that can be an initial step for immune recognition. Thus, comprehension of the chemokine biology in immune responses appears to be fundamental for understanding the pathogenesis of T cell-mediated immune responses. The following review will highlight the current insight into the role of chemokines and their receptors in the cell-mediated immune response, with a special focus on lung diseases., (Copyright 2001 Wiley-Liss, Inc.)

Transcript expression of 24 chemokines (CKs) was examined throughout 8 days in mouse lungs with type-1 (Th1) or type-2 (Th2) cytokine-mediated granulomas induced by bead-immobilized mycobacterial purified protein derivative or Schistosoma mansoni egg antigens. Where possible, CK protein levels were also measured. In addition, we examined effects of in vivo cytokine depletions. Findings were as follows: 1) bead challenge induced increases in 18 of 24 CK transcripts with type-1 and type-2 responses displaying different patterns. CKs fell into four categories: a) type-1-dominant (gamma-interferon-inducible protein (IP-10), monokine induced by INF-gamma (MIG), macrophage inflammatory protein-2 (MIP-2), lipopolysaccharide-induced chemokine (LIX), rodent growth-related oncogene homologue (KP), macrophage inflammatory protein-1alpha (MIP-1alpha) and -1beta (MIP-1beta), lymphotactin), b) type-2-dominant (eotaxin, monocyte chemotactic protein-2 (MCP-2) and -3 (MCP-3), liver and activation-regulated chemokine (LARC), T cell activation protein-3 (TCA-3), c) type-1 and type-2 co-dominant (MCP-1, MCP-5, monocyte-derived chemokine (MDC), thymus and activation-related chemokine (TARC), C10), and d) constitutive (lungkine, secondary lymphoid-tissue chemokine (SLC), EBI1-ligand chemokine (ELC), fractalkine, macrophage inflammatory protein-1gamma (MIP1-gamma), and stromal cell derived factor-1alpha (SDF1-alpha). 2) CKs displayed characteristic temporal patterns. CXC (IP-10, MIG, MIP-2, LIX, KC) and certain CC (MCP-1, MCP-5, MIP-1alpha, MIP-1beta) CKs were produced maximally within 1 to 2 days. Others (MCP-2, MCP-3, eotaxin, lymphotactin, LARC, TCA-3) displayed peak expression later. 3) Interferon-gamma neutralization profoundly abrogated MIG, but had little effect on other CKs. Tumor necrosis factor-alpha neutralization caused up to 50% reduction in a range of CKs. These findings indicate that type-1 and type-2 granulomas display characteristic CK profiles with coordinated expression that is under cytokine-mediated regulation.

The contribution of IL-4 and IL-13 to inflammation and cytokine responses was compared in mice with types-1 or -2 pulmonary granulomas (GR) elicited by beads bound to antigens of Mycobacteria bovis (PPD) or Schistosoma mansoni eggs (SEA). Type-2 SEA-GR produced the most IL-4 and IL-13. Type-1 PPD-GR produced detectable IL-13, but not IL-4. Mice were treated with anti-IL4 or anti-IL-13 Abs, then lesion size/composition, cytokine/chemokine mRNA and lymph node cytokines were measured. Type-1 GRs resisted individual Abs, but combined Abs augmented lesions by 20%. In contrast, anti-IL-4 abrogated type-2 GR by 30-40% and eosinophil recruitment by 60%. Anti-IL-13 abrogated type-2 GR by 20-30% with no effect on eosinophils. Combined depletion reduced lesion area by 60% and eosinophils by more than 80%. In type-1 GR lungs, anti-IL-4 and anti-IL-13 augmented IFNgamma and TNFalpha mRNA. In type 2 lungs, anti-IL-13 did likewise, but anti-IL-4 decreased TNFalpha without affecting IFNgamma mRNA. In both responses, IL-4 promoted MCP-1 and MCP-5 mRNA, but IL-13 inhibited chemokines in type-1 GR. In lymph nodes, anti-IL-4, but not anti-IL-13, abrogated type-2 cytokines. In fact, IL-13 down-regulated itself and other type-2 cytokines. In summary, IL-4 and IL-13 have common and disparate regulatory functions in types 1 and 2 responses.

During the last decade, our understanding of the mechanisms involved in the initiation and maintenance of pulmonary disease has been greatly aided by advances in the field of chemokine biology. Chemokines comprise four supergene families, two of these families (the CC and CXC chemokine groups) are quite large and contain over 50 identified ligands and at least 14 individual receptors. Two additional chemokine families (C, CXXXC chemokines) are small and contain lymphotactin and fractalkine, respectively, as their members. In addition to their originally identified chemotactic activity, chemokines possess a variety of biological activities, ranging from immunomodulating leukocyte activation to suppressing HIV infection. The latter effect is due to the ability of specific chemokine receptors to serve as co-receptor for HIV entry into specific leukocyte sub-populations. A number of in vitro and in vivo studies have underscored the importance of chemokine biology in the progression of both acute and chronic lung diseases. These investigations have demonstrated the importance of targeting chemokines for new therapeutic approaches to treat pulmonary disease. A variety of acute and chronic lung diseases have been shown to possess a chemokine component and contribute to the initiation and maintenance of lung pathology, thus, there is little doubt that a further understanding of the mechanisms of pulmonary diseases will rely upon advances in the field of chemokine biology.

Background: Regardless of its involvement in either wound healing or excessive fibrosis, the interstitial fibroblast can now be considered an important early participant in inflammatory responses. Although it is recognized that certain immune cells and proinflammatory mediators are intricately linked to fibrotic disease, little is presently known about the manner in which these mediators and cells are orchestrated to a fibrotic finale. Experimental studies have shown that interstitial fibroblasts are capable of participating in an inflammatory response by promoting direct fibroblast-to-immune cell communication and/or modulating the release of soluble mediators that are mutually recognized by both types of cells., Methods: Primary cultures of murine fibroblasts were recovered from either normal tissue or tissue undergoing a cell-mediated inflammatory response. These stromal cells were assessed for the expression of various cytokines and chemokines indicative of a type 1 or type 2 response. In addition, the fibroblasts were co-cultured with mononuclear cells to assess the cell-to-cell communication., Results: Fibroblasts recovered from different cell-mediated inflammatory responses demonstrated a dramatic alteration in their cytokine profile. Fibroblasts recovered from the type 2 immune response produced high levels of monocyte chemotactic protein-1 (MCP-1), as compared to the normal fibroblasts and fibroblasts recovered from the type 1 lesion. Mononuclear cells co-cultured with fibroblasts induced a contact-dependent expression of elevated levels of chemokines, especially the macrophage-derived MIP-1 alpha. Thus, both fibroblasts themselves and fibroblasts co-cultured with immune-inflammatory cells have the ability to participate in the maintenance of an inflammatory response via the expression of chemokines., Conclusions: Our laboratory and others have addressed the role of chemotactic cytokines or chemokines in the fibrotic process, and have demonstrated that fibroblasts are capable of modulating the activation of various immune cells that have been implicated in fibrotic disease. In addition, the interstitial fibroblast is capable of regulating its own behavior within the interstitial environment via the expression of chemokines and chemokine receptors. Thus, novel strategies aimed at preventing fibrotic disease will likely need to address the early engagement of inflammatory cells by fibroblasts, and possibly modulate the ability of fibroblasts to generate and/or recognize profibrotic signals supplied by chemokines.

Type 1 (IFN-gamma/TNF-dominant) and 2 (IL-4/IL-5-dominant) granulomatous inflammation were analyzed in mice with knockout of IFN-gamma or IL-4 genes. Lung granulomas were elicited by beads coated with purified protein derivative (PPD) of Mycobacteria bovis or soluble Schistosoma mansoni egg Ags. Parameters included granuloma size, composition, and macrophage function; white blood cell differentials; lymph node cytokine profiles; and cytokine/chemokine mRNA expression by lungs. Type 1 (PPD) and 2 (soluble Schistosoma mansoni egg Ags) responses showed characteristic cytokine and chemokine profiles in control mice. IFN-gamma knockout converted the PPD response to a type 2-like pattern with eosinophil infiltration and decreased TNF and RANTES, but increased IL-4, IL-5, IL-10, IL-13, monocyte chemoattractant protein-3 (MCP-3), and eotaxin expression. IL-4 knockout exacerbated type 1 inflammation with increased IL-2/IFN-gamma production by lymph nodes and IL-1 production by granuloma macrophages, but unexpectedly, IFN-gamma transcripts were reduced in lungs. Regarding the type 2 response, IL-4 was needed for maximal blood eosinophilia, but surprisingly, its absence had a minimal effect on type 2 granuloma size and composition despite regional reductions of IL-5 and IL-10 as well as local reductions of TNF-alpha, MCP-1, MCP-3, and eotaxin. Thus, the type 2 granuloma was not converted to a type 1 composition with IL-4 knockout, but showed persistent expression of IL-13 and some degree of IL-5 and MCP-3, suggesting that these cytokines could potentially support a compensatory type 2 response. IFN-gamma knockout did not augment type 2 granuloma size or Th2 cytokines in lymph nodes and unexpectedly reduced IL-4 transcripts in lungs. This study offers important implications regarding inflammation and its relationship to local and regional cytokine expression.

The expression of cytokines can dictate the intensity, chronicity, and type of immune/inflammatory response that is produced. These events may be regulated by accumulation of particular cell populations at a site of immune response that can be regulated by the expression of specific chemokines. Recent data have indicated that chemokines also have direct effects on cellular activation. In particular, T lymphocyte responses have been divided into two distinct phenotypes, designated by TH1- and TH2-type cytokine expression. Although it is recognized that divergent T-lymphocyte-derived cytokine phenotypes exist, the mechanisms that dictate the expression of these cytokines and ultimately the division of these immune responses is not entirely clear. In the present study, we present data that the C-C chemokine family members may be a factor influencing the direction of T-cell-derived lymphokine production. To elucidate the role of C-C chemokines, MIP-1 alpha and MCP-1, we have used both antigen-specific (schistosomal egg antigen (SEA)) and nonspecific (conconavalin (Con) A) stimuli. Using TH2-type lymphocyte populations from SEA-sensitized mice, a significant increase in IL-4 mRNA expression and protein production was observed when MCP-1 was added to the culture. Conversely, MIP-1 alpha treatment appeared to decrease interleukin (IL)-4 production. Interestingly, the proliferative response in the TH2-type (SEA-specific) response was up-regulated by MIP-1 alpha whereas MCP-1 down-regulated the response, inversely correlating with IL-4 production. Primary stimulation of naive lymphocytes with Con A induces a predominant interferon (IFN)-gamma response, whereas the second stimulation of the same lymphocytes with Con A induces both IFN-gamma and IL-4. When the two C-C chemokines were individually co-incubated with Con-A-stimulated lymphocytes, both up-regulated IFN-gamma production and proliferation during the primary stimulation. Similarly, in the secondary response, both chemokines further upregulated IFN-gamma production; however, only MCP-1 co-stimulation increased IL-4 production, whereas MIP-1 alpha significantly decreased IL-4 production in these same cell populations. These results were also reflected in steady-state levels of mRNA expression. These results suggest that the production of C-C chemokines (MCP-1 or MIP-1 alpha) during an immune response may aid in determining the type of cytokines produced and the level of lymphocyte activation during a particular response.

Allergic airway inflammation is characterized by peribronchial eosinophil accumulation with the submucosa surrounding the airway. The initial induction of immunoglobulin E (IgE)-mediated mast cell degranulation, up-regulation of adhesion molecules, and the production of inflammatory and chemotactic cytokines, leading to the infiltration of specific leukocyte subsets, is orchestrated in a sequential manner. The activation and degranulation of local mast cell populations is an immediate airway response mediated both by antigen-specific, surface bound IgE and by cytokine-induced activational pathways. Subsequently the infiltration and activation of effector leukocytes (neutrophils and eosinophils) mediated by the persistent activation of allergen-specific T cells leads to pathological manifestations within the lung and airway. The development of appropriate animal models to dissect the critical mechanisms involved in antigen-induced airway pathology is crucial for the development of efficacious therapies. We have utilized a model of allergic airway inflammation induced by intratracheal challenge with parasite (Schistosoma mansoni) egg antigen in presensitized mice. This model has proven useful in the assessment of eosinophil recruitment and has identified key cytokines involved in leukocyte elicitation. These cytokines include interleukin-4 and elicitation. These cytokines include interleukin-4 and tumor necrosis factor, which appear to act as early response mediators, as well as C-C chemokines, macrophage inflammatory protein-1a, and RANTES, which act directly on eosinophil recruitment. In addition, we have found that both C-X-C and C-C chemokines are expressed in pulmonary-derived mast cells, suggesting an important contribution to leukocyte responses in the allergic airway.

Chemokine receptors transduce signals important for the function and trafficking of leukocytes. Recently, it has been shown that CC chemokine receptor (CCR)8 is selectively expressed by Th2 subsets, but its functional relevance is unclear. To address the biological role of CCR8, we generated CCR8 deficient (-/-) mice. Here we report defective T helper type 2 (Th2) immune responses in vivo in CCR8(-/)- mice in models of Schistosoma mansoni soluble egg antigen (SEA)-induced granuloma formation as well as ovalbumin (OVA)- and cockroach antigen (CRA)-induced allergic airway inflammation. In these mice, the response to SEA, OVA, and CRA showed impaired Th2 cytokine production that was associated with aberrant type 2 inflammation displaying a 50 to 80% reduction in eosinophils. In contrast, a prototypical Th1 immune response, elicited by Mycobacteria bovis purified protein derivative (PPD) was unaffected by CCR8 deficiency. Mechanistic analyses indicated that Th2 cells developed normally and that the reduction in eosinophil recruitment was likely due to systemic reduction in interleukin 5. These results indicate an important role for CCR8 in Th2 functional responses in vivo.