IntroductionDendritic cells (DCs) are professional antigen-presenting cells and key regulators of T-cell functions. 1,2 In the airway epithelium, DCs form an extensive network, where they continuously sense environmental antigens. After antigen capture, lung DCs migrate to mediastinal lymph nodes, where antigens are presented to T cells. Activation of a T helper cell 2 (Th2)-skewed response by airway DCs is responsible for allergic immune responses in the lung. 3,4 Chemokine receptors play a crucial role in the migration of maturing DCs to secondary lymphoid organs, 5,6 and several studies have shown that this process is a crucial event for the appropriate activation of the immune response. 7-10 DC migration to lymph nodes relies on the functional expression of CCR7 5,6 as well as other chemotactic receptors, such as CCR8 and BLT1. [9][10][11] In addition, lung DC migration is also regulated by PD1, one of the 2 PGD2 receptors, and by the transcription factors PPR␥ and Runx3. [12][13][14] However, as a difference from DCs localized in other anatomical compartments, the homing of lung DCs to lymph nodes is independent of the action of MRP1, the LTC4 transporter that regulates CCR7 functions. 11 This finding indicates that DC trafficking is regulated in a tissue-specific manner.Chemokine CC motif receptor-like 2 (CCRL2), also known as L-CCR (lipopolysaccharide [LPS]-inducible CC chemokinerelated gene and Eo1), is a heptahelic serpentine receptor that shares the highest homology with the chemokine receptors, CCR1 and CCR5. CCRL2 is structurally characterized by the presence of a noncanonical DRYLAIV motif. CCRL2 was originally identified in the mouse macrophage cell line RAW 264.7 15 and was recently reported to bind the chemotactic protein chemerin, though in the absence of any detectable intracellular signaling. 16 CCRL2 expression at the mRNA level has been described in murine macrophages, 15 glial cells, astrocytes, and microglia stimulated with LPS 17,18 and in mast cells. 16 CCRL2 was also reported to be up-regulated in lung macrophages and epithelial cells after in vivo sensitization. 19 The human gene most closely related to CCRL2 is HCR with its 2 splicing variants, CRAM-A and CRAM-B.Here, we describe that CCRL2 is rapidly induced during mouse DC maturation with a kinetics that precedes CCR7 induction. To evaluate the relevance of this receptor in DC biology, we generated CCRL2-deficient mice and used them in an established model of allergen-induced airway inflammation, in which DCs are known to play a crucial role. 20 The results reported here highlight a nonredundant role for CCRL2 in the migration of lung DCs to regional lymph nodes and in the induction of Th2-oriented airway allergic inflammation. These results propose CCRL2 as a new potential target for therapeutic strategies aimed at controlling lung hypersensitivity. The online version of this article contains a data supplement.The publication costs of this article were defrayed in part by page charge payment. Therefore, and solely to indicate this ...

We investigated possible cellular receptors for the human CXC chemokine platelet factor-4 variant/CXCL4L1, a potent inhibitor of angiogenesis. We found that CXCL4L1 has lower affinity for heparin and chondroitin sulfate-E than platelet factor-4 (CXCL4) and showed that CXCL10 and CXCL4L1 could displace each other on microvascular endothelial cells. Labeled CXCL4L1 also bound to CXCR3A-and CXCR3B-transfectants and was displaced by CXCL4L1, CXCL4, and CXCL10. The CXCL4L1 anti-angiogenic ac- IntroductionThe chemokine family of chemotactic cytokines consists of rather small proteins (7-12 kDa) that signal via G protein-coupled receptors, designated CC chemokine receptor (CCR) or CXC chemokine receptor (CXCR), and regulate leukocyte recruitment to inflammatory sites, as well as leukocyte traffic between immunological compartments. Other target cells of chemokines include tumor cells and endothelial cells, and consequently, chemokines play a role in tumor development. 1,2 For example, the CXCR3 ligands CXCL9, CXCL10, and CXCL11 are chemotactic for antitumoral lymphocytes and inhibit angiogenesis. However, some members of the chemokine family (eg, the CXCR2 ligands CXCL1, CXCL2, CXCL3, CXCL5, CXCL6, and CXCL8) favor tumor growth by attracting neutrophils, by stimulating the release of matrix metalloproteinases, by acting as growth factors, and by promoting angiogenesis. One of the first chemokines that was investigated as an anticancer therapeutic is CXCL4 or platelet factor-4. [1][2][3] The human CXC chemokine platelet factor-4 (CXCL4) is encoded by 2 genes, located on chromosome 4 and probably arose through duplication. 4,5 The 2 genes are indeed highly related and give rise to mature proteins that differ in only 3 amino acid residues in the carboxylic acid (COOH)-terminal part. Analysis of conditioned media from thrombin-treated platelets revealed that both CXCL4 genes are translated into proteins. 6 Afterward, tumor cells and smooth muscle cells were identified as alternative cellular sources for CXCL4L1 but not for CXCL4, indicating that not every cell type that produces CXCL4 also releases CXCL4L1 and vice versa. 7,8 The fact that tumor cells produce angiostatic CXCL4L1 provides a negative feedback on tumor growth, because CXCL4L1 is more potent than CXCL4 in angiostatic assays. 6 In this manuscript, we confirm that the antitumoral activity of CXCL4L1 is exerted through inhibition of angiogenesis and demonstrate that this angiostatic activity is CXCR3-dependent in human and mouse models. Furthermore, we also show for the first time that CXCL4L1 attracts human and mouse activated T lymphocytes, human dendritic cells (DCs), and human natural killer (NK) cells and that CXCL4L1-induced chemotaxis of immature DCs is mediated by CXCR3, coupling to a G ␣i protein. In addition to CXCR3A and CXCR3B interaction, binding to glycosaminoglycans (GAGs) was explored as well. MethodsA supplemental Methods section is available on the Blood Web site (see the Supplemental Materials link at the top of the online article). All animal...

Molluscum contagiosum virus (MCV) infection induces self-limiting cutaneous lesions in an immunocompetent host that can undergo spontaneous regression preceded by local inflammation. On histology, a large majority of MCV-induced lesions are characterized by islands of hyperplastic epithelium containing infected keratinocytes and surrounded by scarce inflammatory infiltrate. However, spontaneous regression has been associated with the occurrence of a dense inflammatory reaction. By histology and immunohistochemistry, we identified MCV-induced lesions showing a dense inflammatory infiltrate associated with cell death in keratinocytes (inflammatory Molluscum contagiosum (I-MC)). In I-MC, hyperplastic keratinocytes were highly immunogenic as demonstrated by the expression of major histocompatibility complex class I and II molecules. Immune cell infiltration consisted of numerous cytotoxic T cells admixed with natural killer cells and plasmacytoid dendritic cells (PDCs). Accordingly, a type I IFN signature associated with PDC infiltration was demonstrated in both keratinocytes and inflammatory cells. Among the latter, a cell population resembling IFN-DC (CD123(+)CD11c(+)CD16(+)CD14(+)MxA(+)) was identified in proximity to islands of apoptotic keratinocytes. In vitro-generated IFN-DCs expressed a strong cytotoxic signature, as demonstrated by high levels of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and Fas ligand (FasL). This study establishes a previously unreported model to underpin the role of innate immune cells in viral immune surveillance.

OM-85 (Broncho-Vaxom®, Broncho-Munal®, Ommunal®, Paxoral®, Vaxoral®), a product made of the water soluble fractions of 21 inactivated bacterial strain patterns responsible for respiratory tract infections, is used for the prevention of recurrent upper respiratory tract infections and acute exacerbations in chronic obstructive pulmonary disease patients. OM-85 is able to potentiate both innate and adaptive immune responses. However, the molecular mechanisms responsible for OM-85 activation are still largely unknown. Purpose of this study was to investigate the impact of OM-85 stimulation on human dendritic cell functions. We show that OM-85 selectively induced NF-kB and MAPK activation in human DC with no detectable action on the interferon regulatory factor (IRF) pathway. As a consequence, chemokines (i.e. CXCL8, CXCL6, CCL3, CCL20, CCL22) and B-cell activating cytokines (i.e. IL-6, BAFF and IL-10) were strongly upregulated. OM-85 also synergized with the action of classical pro-inflammatory stimuli used at suboptimal concentrations. Peripheral blood mononuclear cells from patients with COPD, a pathological condition often associated with altered PRR expression pattern, fully retained the capability to respond to OM-85. These results provide new insights on the molecular mechanisms of OM-85 activation of the immune response and strengthen the rational for its use in clinical settings.

IntroductionActivin A is a homodimeric protein that belongs to the transforming growth factor (TGF)-␤ family. Activin A signals through heterodimeric transmembrane serine/threonine kinase receptor complexes consisting of type I (ALK 2, 4, or 7) and type II receptors (ActRIIA and ActRIIB), which share the intracellular Smad signaling pathway with the TGF-␤ receptors. Activin A also binds follistatin, a protein that controls the biologic activity of Activin A acting as a decoy receptor. 1,2 Activin A was initially identified for its ability to control the secretion of follicle-stimulating hormone, 2 and then found to be a differentiating and trophic factor for embryonic tissues during ontogenesis and wound repair. 3,4 However, emerging evidence proposes activin A is also a key mediator of inflammation. In vivo inoculation of lipopolysaccharide (LPS) induces a rapid increase of activin A circulating levels. This increase precedes and is independent of proinflammatory cytokine and prostaglandin production. 4 In vitro, many cell types produce activin A in response to proinflammatory cytokines and/or LPS, and activin A by itself was reported to potently stimulate the production of inflammatory cytokines and nitric oxide. 4 Dendritic cells (DCs) are highly specialized antigen-presenting cells that play a crucial role in the initiation of innate and adaptive immune responses 5-7 and shape inflammatory responses through the production of proinflammatory cytokines and chemokines. 5,8 DCs accumulate at the site of inflammation in response to the local production of inflammatory chemokines. In turn, the exposure of DCs to proinflammatory agonists induces their migration to regional lymph nodes, where they localize to the paracortical area by a C-C chemokine receptor 7-dependent mechanism. 8,9 Recent data from us and others suggest a key role for activin A in regulating DC function. Stimulation of DCs in vitro with proinflammatory cytokines and bacterial agonists produces significant amounts of activin A. 3,10 Furthermore, high levels of activin A were detected in vivo at sites of tissue repair such as hypertrophic scars, as well as in certain autoimmune diseases like oral lichen planus 11 and inflammatory bowel disease. 12 Activin A was also shown to regulate cytokine production by DCs and to attenuate the expansion of viral antigen-specific effector CD8 ϩ T cells. 10 Furthermore, activin A was reported to induce the differentiation of Langerhans cells from circulating and skin-resident precursor cells. 11 Because in vivo the expression of activin A is associated with an increased tissue infiltration by DCs,11,13,14 the aim of this study was to investigate the possible role of activin A in DC migration. In this study, we show that activin A selectively promotes in vitro directional migration of immature myeloid DCs (iDCs) through a complex mechanism involving polarized chemokine production that differentiates the action of activin A from that of TGF-␤ and classical chemotactic factors. Methods Cytokines and reagentsHuman gr...