Chemokines CCL19 and CCL21 promote activation-induced cell death of antigen-responding T cells

Secondary lymphoid organs (SLOs) provide a niche for the initiation and regulation of T-cell responses, but the mechanisms have been poorly understood. We investigated the influence of chemokines CCL19 and CCL21 constitutively expressed in SLOs on activation-induced cell death (AICD) of CD4+ T cells. When paucity of lymph node T cells (plt) mutant mice lacking expression of CCL19/CCL21 were primed with OVA/CFA, both expansion of OVA-responding CD4+ T cells in the draining lymph nodes and an in vitro recall response were prolonged as compared with responses in wild-type (WT) mice. The apoptotic cell frequency among OVA-responding CD4+ T cells was similarly low in plt/plt and WT mice during the clonal expansion phase. However, during the clonal contraction phase, the frequency never increased in plt/plt mice, whereas in WT mice it continuously increased to a peak 18 days after immunization. The presence of CCL19/CCL21 during the in vitro stimulation of CD4+ T cells with anti-CD3 plus anti-CD28 significantly enhanced in vitro AICD induction of the restimulated T cells, partially through enhancing expression of Fas ligand. Our results suggest that CCL19/CCL21 produced by stromal cells and antigen-presenting cells regulate CD4+ T-cell immune responses in SLOs by promoting AICD.

CCL5 evokes calcium signals in microglia through a kinase-, phosphoinositide-, and nucleotide-dependent mechanism

Microglia, the resident macrophages of the CNS, are responsible for the innate immune response in the brain and participate in the pathogenesis of certain neurodegenerative disorders. Chemokines initiate activation and migration of microglia. The beta-chemokine CCL5 induces an elevation in intracellular calcium concentration ([Ca(2+)](i)) in human microglia. Here, we examined the signal transduction pathway linking activation of chemokine receptor CCR5 to an elevation in [Ca(2+)](i) in cultured microglia by using pharmacological approaches in combination with Fura-2-based digital imaging. The CCL5-induced response required Janus kinase (Jak) activity and the stimulation of an inhibitory G protein. Multiple downstream signaling pathways were involved, including phosphatidylinositol 3-kinase (PI3K), Bruton's tyrosine kinase (Btk), and phospholipase C (PLC)-mediated release of Ca(2+) from inositol 1,4,5-trisphosphate (IP(3))-sensitive stores. Activation of both the kinase and the lipase pathways was required for eliciting the Ca(2+) response. However, the majority of the [Ca(2+)](i) increase was derived from sources activated by NAD metabolites. Cyclic ADP-ribose (cADPR) evoked Ca(2+) release from intracellular stores, and ADPR evoked Ca(2+) influx via a nimodipine-sensitive channel. Thus, a multistep cascade couples CCR5 activation to Ca(2+) increases in human microglia. Because changes in [Ca(2+)](i) affect chemotaxis, secretion, and gene expression, pharmacologic modulation of this pathway may alter inflammatory and degenerative processes in the CNS.

Hierarchy of eosinophil chemoattractants: role of p38 mitogen-activated protein kinase

Several chemoattractants can regulate the recruitment of eosinophils to sites of inflammation, but the hierarchy among them is unknown. We observed here that eosinophil chemotaxis towards eotaxin or 5-oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE) was amplified up to sixfold in the presence of prostaglandin (PG) D2. This effect was only seen in eosinophils, and not in neutrophils or basophils. Pretreatment with the chemoattractant receptor-homologous molecule expressed on TH2 cells (CRTH2) antagonist ramatroban prevented the PGD2 enhancement of eosinophil migrations. In contrast, eotaxin or 5-oxo-ETE inhibited the migration of eosinophils towards PGD2. 5-oxo-ETE enhanced the chemotaxis to eotaxin, while eotaxin had no effect on 5-oxo-ETE-induced migration. 5-oxo-ETE induced the phosphorylation of p38 mitogen-activated protein kinase, and inhibition of p38 mitogen-activated protein kinase by SB-202190 converted the effect of 5-oxo-ETE on the chemotaxis to PGD2 from inhibition to enhancement. The presence of blood or plasma markedly decreased the sensitivity of eosinophils to eotaxin or 5-oxo-ETE, while responses to PGD2 were unaltered. In conclusion, PGD2 might be an initial chemoattractant, since it maintains its potency in the circulation and augments the responsiveness of eosinophils to other chemoattractants. In contrast, eotaxin seems to be an end-point chemoattractant, since it has reduced efficacy in blood and is capable of down-modulating eosinophil responsiveness to other chemoattractants.

A dominant role for FcgammaRII in antibody-enhanced dengue virus infection of human mast cells and associated CCL5 release

Dengue virus is a major mosquito-borne human pathogen with four known serotypes. The presence of antidengue virus antibodies in the serum of individuals prior to dengue virus infection is believed to be an important risk factor for severe dengue virus disease as a result of the phenomenon of antibody-dependent enhancement operating on Fc receptor (FcR)-bearing cells. In addition to blood monocytes, mast cells are susceptible to antibody-enhanced dengue virus infection, producing a number of inflammatory mediators including IL-1, IL-6, and CCL5. Using the human mast cell-like lines KU812 and HMC-1 as well as primary cultures of human cord blood-derived mast cells (CBMC), we aimed to identify the participating FcRs in antibody-enhanced mast cell dengue virus infection, as FcRs represent a potential site for therapeutic intervention. CBMC expressed significant levels of FcgammaRI, FcgammaRII, and FcgammaRIII, and mast cell-like HMC-1 and KU812 cells expressed predominantly FcgammaRII. All four serotypes of dengue virus showed antibody-enhanced binding to KU812 cells. Specific FcgammaRII blockade with mAb IV.3 was found to significantly abrogate dengue virus binding to KU812 cells and CBMC in the presence of dengue-specific antibody. Dengue virus infection and the production of CCL5 by KU812 cells were also inhibited by FcgammaRII blockade.

Altered thymocyte migration during experimental acute Trypanosoma cruzi infection: combined role of fibronectin and the chemokines CXCL12 and CCL4

We previously showed migration disturbances in the thymus during experimental infection with Trypanosoma cruzi, the causative agent of Chagas disease. These changes were related to the enhanced expression of extracellular matrix ligands and receptors, leading to the escape of immature cells to the periphery. Here, we analyzed the expression and role of selected chemokines (CXCL12 and CCL4) and their receptors (CXCR4 and CCR5) in regulating thymocyte migration in conjunction with extracellular matrix during acute T. cruzi infection. We found increased chemokine deposition in the thymus of infected mice when compared to controls, accompanied by enhanced co-localization with fibronectin as well as up-regulated surface expression of CXCR4 and CCR5 in thymocytes. We also noticed altered thymocyte migration towards the chemokines analyzed. Such an enhancement was even more prominent when fibronectin was added as a haptotatic stimulus in combination with a given chemokine. Our findings suggest that thymocyte migration results from a combined action of chemokines and extracellular matrix (ECM), which can be altered during pathological conditions such as T. cruzi infection, and may be at the origin of the changes in the T cell repertoire seen in this pathological process.

Eosinophil-selective mediators in human strongyloidiasis

Strongyloides stercoralis infection is characterized by the production of IgE and eosinophils in peripheral blood. Experimental studies have demonstrated that eosinophils play an important role in protection against Strongyloides stercoralis, but the mechanisms regulating eosinophils are not known. In this study we have focused on analysing the molecules that selectively regulate eosinophil migration, namely eotaxin and interleukin-5 (IL-5), using an enzyme-linked immunosorbent assay in patients with strongyloidiasis. Serum expression of eotaxin and IL-5 were significantly increased in patients compared with the control group. This rise suggests that selective mediators of the eosinophil can have a role in immunity against S. stercoralis in human infection.

Analysis of Antitumor Activity Elicited by Vaccination with Combinations of Interleukin-12 DNA with gp100 DNA or the Chemokine CCL21In Vivo

The antitumor efficacy of human melanoma-associated antigen (hgp100) and chemokine CCL21 in combination with interleukin-12 (IL-12) was evaluated in a syngeneic melanoma mouse model. The rationale for this approach was based on previous studies showing that the efficacy of IL-12 therapy in melanoma patients correlated with the presence of antibodies against tumor-associated antigens. We have previously shown that application of xenogeneic human gp100 DNA (hgp100 DNA) is protective against mouse B16 melanoma. Furthermore, the chemokine CCL21 has the ability to chemoattract both dendritic cells (DCs) and T lymphocytes. We show here that intratumoral injection of IL-12-encoding DNA (IL-12 DNA) in combination with hgp100- encoding DNA (hgp100 DNA) into tumor-bearing mice led to a strong antitumor effect. Coapplication of IL- 12 DNA with CCL21-encoding DNA (CCL21 DNA) or recombinant CCL21 (recCCL21) protein also showed some efficacy. Triple therapy with IL-12 DNA, hgp100 DNA, and CCL21 DNA, however, showed less effect on tumor growth than double therapy with IL-12 DNA and hgp100 DNA. These findings open a new route of investigation of IL-12 and gp100 or other tumor-associated antigens in the immunotherapy of a variety of tumors.

Expression of CCL20 and granulocyte-macrophage colony-stimulating factor, but not Flt3-L, from modified vaccinia virus ankara enhances antiviral cellular and humoral immune responses

While modified vaccinia virus Ankara (MVA) is currently in clinical development as a safe vaccine against smallpox and heterologous infectious diseases, its immunogenicity is likely limited due to the inability of the virus to replicate productively in mammalian hosts. In light of recent data demonstrating that vaccinia viruses, including MVA, preferentially infect antigen-presenting cells (APCs) that play crucial roles in generating antiviral immunity, we hypothesized that expression of specific cytokines and chemokines that mediate APC recruitment and activation from recombinant MVA (rMVA) vectors would enhance the immunogenicity of these vectors. To test this hypothesis, we generated rMVAs that express murine granulocyte-macrophage colony-stimulating factor (mGM-CSF), human CCL20/human macrophage inflammatory protein 3alpha (hCCL20/hMIP-3alpha), or human fms-like tyrosine kinase 3 ligand (hFlt3-L), factors predicted to increase levels of dendritic cells (DCs), to recruit DCs to sites of immunization, or to promote maturation of DCs in vivo, respectively. These rMVAs also coexpress the well-characterized, immunodominant lymphocytic choriomeningitis virus nucleoprotein (NP) antigen that enabled sensitive and quantitative assessment of antigen-specific CD8(+) T-cell responses following immunization of BALB/c mice. Our results demonstrate that immunization of mice with rMVAs expressing mGM-CSF or hCCL20, but not hFlt3-L, results in two- to fourfold increases of cellular immune responses directed against vector-encoded antigens and 6- to 17-fold enhancements of MVA-specific antibody titers, compared to those responses elicited by nonadjuvanted rMVA. Of note, cytokine augmentation of cellular immune responses occurs when rMVAs are given as primary immunizations but not when they are used as booster immunizations, suggesting that these APC-modulating proteins, when used as poxvirus-encoded adjuvants, are more effective at stimulating naïve T-cell responses than in promoting recall of preexisting memory T-cell responses. Our results demonstrate that a strategy to express specific genetic adjuvants from rMVA vectors can be successfully applied to enhance the immunogenicity of MVA-based vaccines.

CCR6 and CCL20: Partners in Intestinal Immunity and Lymphorganogenesis

The CCR6 chemokine receptor is expressed by most B cells and subsets of T cells and dendritic cells (DCs) found in the gut mucosal immune system. CCL20, the single chemokine ligand for CCR6, is selectively made by the follicle-associated epithelium (FAE) overlying Peyer's patches (PPs) and isolated lymphoid follicles (ILFs). CCL20 contributes to the recruitment of CCR6-expressing B cells to these structures. CCL20 expression by the intestinal epithelium is also highly inducible in response to inflammatory stimuli. Thus, CCL20 functions as both an inflammatory and homeostatic chemokine. Interactions between CCR6 and CCL20 play a role at several stages in the development of intestinal lymphoid structures. A subset of the c-kit(+) lymphoid precursors found in cryptopatches (CPs) expresses CCR6. Recruitment of B cells to CPs and the subsequent expansion and organization of these B cells allows differentiation of some of these structures into ILFs. In CCR6 knockout mice, PPs are smaller with fewer follicles and the development of ILFs is compromised. These defects in the development of mucosal inductive sites in CCR6-deficient mice are responsible for decreased IgA production to oral antigens. CCR6 can be included with CXCR5 and CCR7 in a list of chemokine receptors that participate in shaping the organized lymphoid structures that are part of the intestinal immune system.

The role of chemokines in exercise-induced bronchoconstriction in asthma

BACKGROUND

The pathogenesis of exercise-induced bronchoconstriction in asthma is incompletely understood, and the role of chemokines has not been investigated.

OBJECTIVE

To investigate the involvement of the CC chemokines eotaxin, regulated upon activation normal T-cell expressed and secreted (RANTES), thymus and activation-regulated chemokine (TARC), and the CXC chemokine interferon-gamma-inducible protein 10 (IP-10) in exercise-induced bronchoconstriction.

METHODS

Four groups were enrolled: asthmatic children with positive (n = 15) and negative (n = 15) responses to exercise, children with cystic fibrosis (n = 14), and healthy children (n = 11). Levels of eotaxin, RANTES, TARC, and IP-10 were determined in plasma before, immediately after, and 6 and 24 hours after exercise challenge using enzyme-linked immunosorbent assay. Transcriptional activity was measured using reverse transcriptase-polymerase chain reaction.

RESULTS

Exercise did not induce any significant changes in systemic chemokine levels. A significant difference was observed only in the preexercise IP-10 levels among groups (P = .045). There was a significant difference in peripheral blood eosinophil counts among groups (P = .003). In asthmatic children with a positive response to exercise, there was an inverse correlation between eosinophil counts and eotaxin levels (r = -0.616; P = .01) and between forced expiratory volume in 1 second and TARC levels (r = -0.865; P = .001). Reverse transcriptase-polymerase chain reaction studies did not show any difference in the transcription of the chemokines.

CONCLUSIONS

Exercise does not cause any changes in the systemic expression of eosinophilic chemokines. Peripheral blood eosinophils may be a determinant of the exercise response, and eotaxin and TARC may be associated with eosinophil counts and forced expiratory volume in 1 second in children with a bronchoconstrictor response to exercise.

Cytokine expression patterns associated with systemic adverse events following smallpox immunization

Vaccinia virus is reactogenic in a significant number of vaccinees, with the most common adverse events being fever, lymphadenopathy, and rash. Although the inoculation is given in the skin, these adverse events suggest a robust systemic inflammatory response. To elucidate the cytokine response signature of systemic adverse events, we used a protein microarray technique to precisely quantitate 108 serum cytokines and chemokines in vaccine recipients before and 1 week after primary immunization with Aventis Pasteur smallpox vaccine. We studied 74 individuals after vaccination, of whom 22 experienced a systemic adverse event and 52 did not. The soluble factors most associated with adverse events were selected on the basis of voting among a committee of machine-learning methods and statistical procedures, and the selected cytokines were used to build a final decision-tree model. On the basis of changes in protein expression, we identified 6 cytokines that accurately discriminate between individuals on the basis of adverse event status: granulocyte colony-stimulating factor, stem cell factor, monokine induced by interferon-gamma (CXCL9), intercellular adhesion molecule-1, eotaxin, and tissue inhibitor of metalloproteinases-2. This cytokine signature is characteristic of particular inflammatory response pathways and suggests that the secretion of cytokines by fibroblasts plays a central role in systemic adverse events.

Similar functional activity of dendritic cells recruited to the mesenteric lymph nodes of newborn and adult mice after the rectal delivery of Mycobacterium bovis BCG

BCG rectal administration to newborn and adult mice induced protective immune responses against tuberculosis. BCG reaches the sub-epithelial site and the draining mesenteric lymph nodes (MLNs), and dendritic cells (DC) could be recruited to these sites. Using polarized Caco-2 epithelial cells, we showed that BCG translocates epithelial cells to basolateral compartment. Delayed in newborn BALB/c mice, an important recruitment of CD11c+ DCs, was documented in the rectal lamina propria and the MLNs during the first two weeks after rectal BCG delivery. In MLNs, two major DC subtypes were observed: conventional DCs (cDCs) (B220-) and plasmacytoid DCs (pDCs) (B220+). CIRE, mouse DC-specific intracellular adhesion molecule 3 grabbing non-integrin (DC-SIGN) is predominantly expressed on pDCs and at a higher level on pDCs from the adult compared to newborn MLNs. cDCs with a higher capacity to induce the proliferation of naïve CD4+ T cells than pDCs, triggered CD4+ T cells to produce interferon-gamma whereas pDCs triggered them to release interleukin-10. Both DC subtypes equilibrates T cells as a source of microbicidal/microbiostatic signals and those acting as source of counter-inflammatory signals, preventing tissue damage and/or accelerating tissue repair. Thus, rectal delivery of BCG could be a safe and efficient route of vaccination against tuberculosis.

Expression of TECK/CCL25 and MEC/CCL28 chemokines and their respective receptors CCR9 and CCR10 in porcine mucosal tissues

CCL25 and CCL28 (also named TECK and MEC) are CC chemokines primarily expressed by thymic dendritic cells and mucosal epithelial cells. The cognate receptors of CCL25 and CCL28, named CCR9 and CCR10, are mainly expressed on T lymphocytes for CCR9 and IgA(+) and IgM(+) plasmablasts for CCR9 and CCR10, respectively. In human and mouse, chemokines CCL25 and CCL28 play an important role in attracting immune cells to the gastrointestinal tract and in controlling segmental specialization of the intestinal immune system. To investigate if CCL25 and CCL28 play a similar role in the pig and to better understand lymphocyte trafficking in this species, we cloned porcine CCL25 and CCR10 and measured expression of CCL25, CCL28, CCR9, and CCR10 transcripts by real-time and conventional PCR in various tissues from newborn and young piglets, and adult sows. The results of the expression analyses show that (i) expression of CCL25 mRNA is mainly restricted to the small intestine, (ii) CCL28 mRNA expression is detectable in all tested epithelial mucosal surfaces with the highest levels of expression in the mammary gland, trachea and large intestine, (iii) high levels of expression of CCR9 mRNA in CD3+ T lymphocytes, gut-associated lymphoid tissues (GALT), and the small intestine, (iv) high levels of expression of CCR10 mRNA in GALT, the large intestine, the small intestine, and the mammary gland, and (v) up-regulation of CCL28 mRNA expression during lactation in the mammary gland. This pattern of expression, which is discussed in the context of compartmentalization of the porcine common mucosal immune system into upper aero-digestive tract, small intestine and large intestine, suggests a key role for CCL28 in the recruitment of IgA secreting cells into the mammary gland enabling the passive transfer of IgA antibodies from mother to infant.

A possible role for CCL27/CTACK-CCR10 interaction in recruiting CD4 T cells to skin in human graft-versus-host disease

Graft-versus-host disease (GvHD) is a serious complication of allogeneic stem cell transplantation (SCT) affecting the skin, gut and liver. The involvement of distinct organs suggests a role for tissue-specific chemokines and their receptors in directing activated donor T cells to these sites. In this study the potential involvement of the skin-specific CCL27/CTACK-CCR10 interaction was investigated in 15 paediatric SCT patients with skin GvHD. During the course of skin GvHD, peripheral blood T cells from these patients contained a high proportion of CD4+ CCR10+ T cells that disappeared after the GvHD was resolved. These cells were CD45RO+, expressed additional skin homing markers (cutaneous lymphocyte-associated antigen and CCR4), and produced the T-cell helper type 1-cytokines tumour necrosis factor-alpha and interleukin-2. The increase in CD4+ CCR10+ T cells was absent in SCT patients without GvHD. Immunohistochemical investigations showed CD4+ CCR10+ T cells in the GvHD skin biopsies of the same patients, but not in the gut biopsies of patients also suffering from gut GvHD. The infiltration of CD4+ CCR10+ T cells in the GvHD-affected skin correlated with an enhanced epidermal expression of CCL27/CTACK, the ligand for CCR10. These findings support the involvement of CCL27/CTACK-CCR10 interaction in recruiting CD4+ T cells to the skin, thus contributing to the pathogenesis of acute GvHD.

Redundant role of chemokines CCL25/TECK and CCL28/MEC in IgA+ plasmablast recruitment to the intestinal lamina propria after rotavirus infection

Rotaviruses (RV) are the most important cause of severe childhood diarrheal disease. In suckling mice, infection with RV results in an increase in total and virus-specific IgA(+) plasmablasts in the small intestinal lamina propria (LP) soon after infection, providing a unique opportunity to study the mechanism of IgA(+) cell recruitment into the small intestine. In this study, we show that the increase in total and RV-specific IgA(+) plasmablasts in the LP after RV infection can be blocked by the combined administration of Abs against chemokines CCL25 and CCL28, but not by the administration of either Ab alone. RV infection in CCR9 knockout mice still induced a significant accumulation of IgA(+) plasmablasts in the LP, which was blocked by the addition of anti-CCL28 Ab, confirming the synergistic role of CCL25 and CCL28. The absence of IgA(+) plasmablast accumulation in LP following combined anti-chemokine treatment was not due to changes in proliferation or apoptosis in these cells. We also found that coadministration of anti-CCL25 and anti-CCL28 Abs with the addition of anti-alpha(4) Ab did not further inhibit IgA(+) cell accumulation in the LP and that the CCL25 receptor, CCR9, was coexpressed with the intestinal homing receptor alpha(4)beta(7) on IgA(+) plasmablasts. Finally, we showed that RV infection was associated with an increase in both CCL25 and CCL28 in the small intestine. Hence, our findings indicate that alpha(4)beta(7) along with either CCR9 or CCR10 are sufficient for mediating the intestinal migration of IgA(+) plasmablasts during RV infection.

CCR5 usage by CCL5 induces a selective leukocyte recruitment in human skin xenografts in vivo

CCR5 is one of the major inflammatory chemokine receptors with potential therapeutical applications in humans. However, the redundancy of chemokines and their receptors, and the species specificity of chemokine receptor antagonists pose challenges to understanding of the role they play in pharmacological situations. To address this question, we used a humanized severe combined immunodeficient mouse model grafted with human skin and autologous leukocytes, and evaluated the effect of a blocking antibody against human CCR5, on CCL5-induced cutaneous leukocyte recruitment in vivo. At baseline, CCL5 induced a significant recruitment of T cells mainly of the memory phenotype, of monocytes/macrophages, eosinophils, and IFN-gamma(+) but not IL-4(+) and IL-5(+) cells. In vivo, anti-CCR5 antibody was able to almost completely inhibit the recruitment of monocytes/macrophages and T-helper (Th)1-type cells to inhibit partially the attraction of memory T cells, but had no effect on eosinophil infiltration, although all these cell types express other CCL5 binding chemokine receptors than CCR5. These results indicate that the in vivo environment regulates target cell specificity of CCL5 leading to differential cell recruitment, suggesting that antagonizing CCR5 receptor may be of therapeutic value in diseases such as acquired immuno deficiency syndrome, where CCL5/CCR5, monocytes, and Th1-type cells play a predominant role.

The Role of Platelet-Derived Growth Factor Receptor in Eotaxin Signaling of Eosinophils

BACKGROUND

Receptor tyrosine kinases (RTKs) such as epidermal growth factor receptor (EGFR) and platelet-derived growth factor receptor (PDGFR) are capable of eliciting kinase activity after ligand binding. In several cells, RTKs are activated via the G-protein-coupled receptor independent of the ligand-RTK interaction. We have previously found that EGFR is transactivated via CC chemokine receptor 3 in bronchial epithelial cells and that this pathway is important for mitogen-activated protein (MAP) kinase activation and cytokine production. It has recently been suggested that hypereosinophilic syndrome results from the fusion tyrosine kinase FIP1L1-PDGFRA. Although it is possible that the PDGFR signal is involved in eosinophil function, the details are still unclear.

METHODS

Blood eosinophils were purified using Percoll and anti-CD16 antibody-coated magnetic beads. Expression of PDGFR mRNA was examined by RT-PCR. After stimulating eosinophils with eotaxin, the phosphorylation of MAP kinases was examined by Western blotting with the antiphosphospecific MAP kinase antibody. The eotaxin-induced eosinophil chemotaxis was studied using Boyden chambers.

RESULTS

Eosinophils expressed PDGFRbeta mRNA in 4 out of 8 donors, while PDGFRalpha mRNA was expressed in only 1 donor. Protein expression of PDGFR was also detectable in eosinophils from some donors. AG1295, a specific inhibitor of PDGFR, showed dose-dependent inhibition of eotaxin-induced MAP kinase phosphorylation in the eosinophils expressing PDGFRbeta mRNA. The chemotaxis of these eosinophils was significantly inhibited by AG1295 (n = 3).

CONCLUSIONS

Our results suggest that PDGFR modifies the CCR3-MAP kinase signaling pathway and chemotactic response in some donors. The pharmacological targeting of PDGFR may be a new strategy to treat eosinophilic disorders.

A genetic basis for human susceptibility to West Nile virus

West Nile virus (WNV) infects thousands of humans annually and causes a spectrum of disease ranging from an acute febrile illness to lethal encephalitis. A new study suggests a link between CCR5Delta32 (a common mutant allele of the chemokine and HIV receptor CCR5) and fatal WNV infection. The study highlights a possible risk in targeting this receptor for the prevention and/or treatment of infectious diseases.

Effects of Salmonella enterica serovars Typhimurium (ST) and Choleraesuis (SC) on chemokine and cytokine expression in swine ileum and jejunal epithelial cells

The gastrointestinal epithelium represents a barrier to potentially invasive enteric pathogens, maintains a role in innate immune surveillance, and is a source of both chemokine and cytokine chemotactic mediators in response to bacterial invasion. In the current study, we evaluated cytokine and chemokine mediators known to regulate movement of macrophages (macrophage migration inhibitory factor; MIF), neutrophils (IL8), dendritic cells (CCL20), and epithelial remodeling (osteopontin; OPN) in response to invasive swine enteropathogens Salmonella enterica serovar Typhimurium (ST) or Choleraesuis (SC). For the in vivo experiment, weaned pigs served as uninfected controls (0 h) or were given 3 x 10(9) CFU ST orally. Pigs were sacrificed at 8, 24, 48, and 144 h after inoculation and total RNA was extracted from defined segments of proximal (PI) and distal (DI) ileum. Relative expression of MIF and OPN were not affected by ST. IL8 expression was increased numerically (P = 0.17 for the interaction term) at 24 and 144 h in the PI and these increases accounted for greater expression in the PI relative to the DI (P < 0.05). Relative expression of CCL20 was increased at 24 h after ST (P < 0.05). Next, we evaluated the time course of MIF, IL8, CCL20, and OPN mRNA expression induced by application of lipopolysaccharide (LPS), ST or SC in vitro using pig jejunal epithelial cells (IPEC-J2). Cells were grown to confluency on permeable membranes, and treated apically with LPS (10 ng/mL), ST or SC (10(8)/well). After 1 h, cells were washed to remove LPS or extracellular bacteria, and media containing gentamicin was added to kill remaining extracellular bacteria. Media and RNA were collected at 1.5, 3, and 6 h after treatment. MIF mRNA was not affected by LPS or bacterial treatment. Similarly, IL8 expression was not affected by LPS, but was increased by ST and SC relative to controls at 1.5 and 3 h post exposure (P < 0.05 for all comparisons). Treatment with SC increased CCL20 mRNA relative to controls at 3 h (P < 0.05), while ST increased CCL20 at 1.5, 3, and 6h with maximal expression at 6 h (P < 0.05 for all comparisons). ST and SC increased polarized IL8 secretion. Our data demonstrate that invasive bacterial pathogens in the pig gastrointestinal tract trigger upregulation of selected cytokine and chemokine mediators, but serovars of Salmonella elicited differing patterns of activation in vitro.

Specific recruitment of CC chemokine receptor 4-positive regulatory T cells in Hodgkin lymphoma fosters immune privilege

Hodgkin lymphoma (HL) is characterized by the presence of a small number of tumor cells in a rich background of inflammatory cells, but the contribution of the abundant nontumor cells to HL pathogenesis is poorly understood. We showed that migratory CD4(+) cells induced by HL cells were hyporesponsive to T-cell receptor stimulation and suppressed the activation/proliferation of the effector CD4(+) T cells in an autologous setting. We further showed that HL cells in the affected lymph nodes were surrounded by a large number of lymphocytes expressing both CC chemokine receptor 4 (CCR4) and FOXP3. These findings indicate that the migratory cells induced by HL cells function as regulatory T (Treg) cells so that these cells create a favorable environment for the tumor cells to escape from host immune system. In addition, we showed that a chimeric anti-CCR4 monoclonal antibody (mAb) could deplete CCR4(+) T cells and inhibit the migration of CD4(+)CD25(+) T cells in vitro. Recognition of the importance of CCR4(+) Treg cells in the pathogenesis of HL will allow rational design of more effective treatments, such as use of an anti-CCR4 mAb, to overcome the suppressive effect of CCR4(+) Treg cells on the host immune response to tumor cells.

CCL27 is a critical factor for the development of atopic dermatitis in the keratin-14 IL-4 transgenic mouse model

The keratin-14 IL-4 transgenic (Tg) mouse model of atopic dermatitis (AD) is characterized by skin infiltration of T cells, early up-regulation of T(h)2 cytokines and late surge of T(h)1 cytokines. In the present study, we investigated the role of CCL27, a T cell skin-homing chemokine known to be elevated in sera of human AD patients, in disease development in our animal model of AD. The results showed that the mRNA and protein levels of CCL27 in the skin and serum were significantly increased in IL-4 Tg mice. The percentage of T cells expressing CCR10 in skin draining lymph nodes of IL-4 Tg mice was increased, consistent with the findings of >80% of skin-infiltrating T cells in Tg mice expressing CCR10. Chemotaxis transmigration assay demonstrated that CCL27 promotes a greater degree of migration of T cells in diseased Tg mice. Subcutaneous injection of neutralizing anti-CCL27 to IL-4 Tg mice with early skin lesions resulted in reduced clinical progression of inflammation, accompanied with decreased T cell and mast cell infiltration in the skin, and down-regulation of inflammatory cytokines. In conclusion, CCL27 and CCR10 interaction is important for the development of skin inflammation in our AD model.

CCL19 reduces tumour burden in a model of advanced lung cancer

Epstein–Barr virus-induced molecule 1 ligand chemokine (CCL19) is a CC chemokine that chemoattracts both dendritic cells (DC) and T lymphocytes. We evaluated the antitumour efficacy of CCL19 in a murine model of spontaneous bronchoalveolar cell carcinoma. These transgenic mice (CC-10 TAg) express the SV40 large T antigen under the Clara Cell promoter, develop bilateral, multifocal, pulmonary carcinomas and die at 4 months owing to progressive pulmonary tumour burden. To mimic therapy in late-stage disease, 3-month-old transgenic mice were treated with recombinant CCL19 (0.5 μg dose⁻¹) by intranodal (axillary lymph node region) injection three times per week for 4 weeks. CCL19 treatment led to a marked reduction in tumour burden with extensive mononuclear infiltration of the tumours compared to diluent treated controls. Flow cytometric analyses showed significant increases in CD4 and CD8T cell subsets as well as DC in the lungs of CCL19-treated mice. Lung tissue cytokine profiles showed a shift towards immune stimulatory molecules with a decrease in the immunosuppressive cytokine TGF-β. Our findings show that CCL19 may serve as a potential immune stimulator and provide a strong rationale for the evaluation of CCL19 in cancer immunotherapy.

Endothelial and epithelial expression of eotaxin-2 (CCL24) in nasal polyps

BACKGROUND

Nasal polyposis is mostly associated with eosinophilia of mucosal tissue. This points to the implication of CC chemokines in nasal eosinophilia. Recently the CC chemokine eotaxin-2 (CCL24) was identified. This study was initiated to localize the cellular source, analyze expression of mRNA, and quantify protein synthesis of CCL24.

METHODS

Specimens of nasal inferior turbinates from controls and polypous tissue from patients suffering from chronic polypous sinusitis were collected. Furthermore, fibroblasts and epithelial cells were cultured. CCL24 protein was analyzed by immunohistochemistry and ELISA, expression of mRNA by SQ-RT-PCR.

RESULTS

CCL24 was observed in endothelial and epithelial cells. Specimens from patients expressed significantly (>2fold) more CCL24 mRNA than controls. Fibroblasts and unstimulated cells did not express CCL24 mRNA. Upon stimulation with TNF-alpha, INF-gamma, IL-4, or costimulation with TNF-alpha and INF-gamma CCL24 mRNA was significantly enhanced (3.2-19.6%). In controls, fibroblast, and unstimulated cells CCL24 protein was below detection limit. Most polyps comprised significant amounts of CCL24 (mean 0.24 ng/mg). TNF-alpha, INF-gamma or IL-4 induced CCL24 protein (0.1-0.3 ng/ml) in epithelial cells. Costimulation with TNF-alpha and IL-4 (0.1-30 and 1-30 ng/ml, respectively) synergistically induced synthesis of CCL24 protein (0.18-0.31 ng/ml).

CONCLUSION

In nasal polyps endothelial and epithelial cells are obviously the main source of CCL24, which was shown for transcription (mRNA) and production (protein) levels and was associated with diseases. Results gave evidence of CLL24- directed migration of cells from inside (the bloodstream) to the epithelial side (mucosa) in eosinophilic inflammatory diseases, e.g. nasal polyposis.

Intrapulmonary administration of CCL21 gene-modified dendritic cells reduces tumor burden in spontaneous murine bronchoalveolar cell carcinoma

The antitumor efficiency of dendritic cells transduced with an adenovirus vector expressing secondary lymphoid chemokine (CCL21) was evaluated in a murine model of spontaneous bronchoalveolar cell carcinoma. The transgenic mice (CC-10 TAg) express the SV40 large T antigen (TAg) under the Clara cell promoter, develop bilateral, multifocal, and pulmonary adenocarcinomas, and die at 4 months as a result of progressive pulmonary tumor burden. A single intratracheal administration of CCL21 gene-modified dendritic cells (DC-AdCCL21) led to a marked reduction in tumor burden with extensive mononuclear cell infiltration of the tumors. The reduction in tumor burden was accompanied by the enhanced elaboration of type 1 cytokines [IFN-gamma, interleukin (IL)-12, and granulocyte macrophage colony-stimulating factor] and antiangiogenic chemokines (CXCL9 and CXCL10) but a concomitant decrease in the immunosuppressive molecules (IL-10, transforming growth factor-beta, prostaglandin E(2)) in the tumor microenvironment. The DC-AdCCL21 therapy group revealed a significantly greater frequency of tumor-specific T cells releasing IFN-gamma compared with the controls. Continuous therapy with weekly intranasal delivery of DC-AdCCL21 significantly prolonged median survival by >7 weeks in CC-10 TAg mice. Both innate natural killer and specific T-cell antitumor responses significantly increased following DC-AdCCL21 therapy. Significant reduction in tumor burden in a model in which tumors develop in an organ-specific manner provides a strong rationale for further evaluation of intrapulmonary-administered DC-AdCCL21 in regulation of tumor immunity and genetic immunotherapy for lung cancer.

A multistep adhesion cascade for lymphoid progenitor cell homing to the thymus

Homing of bone marrow (BM)-derived progenitors to the thymus is essential for T cell development. We have previously reported that two subpopulations of common lymphoid progenitors, CLP-1 and CLP-2, coexist in the BM and give rise to lymphocytes. We demonstrate that CLP-2 migrate to the thymus more efficiently than any other BM-derived progenitors. Short-term adoptive transfer experiments revealed that CLP-2 homing involves P-selectin/P-selectin glycoprotein ligand 1 interactions, pertussis toxin-sensitive chemoattractant signaling by CC chemokine ligand 25 through CC chemokine receptor 9, and binding of the integrins alpha4beta1 and alphaLbeta2 to their respective ligands, vascular cell adhesion molecule 1 and intercellular adhesion molecule 1. Preferential thymus-tropism of CLP-2 correlated with higher chemokine receptor 9 expression than on other BM progenitors. Thus, CLP access to the thymus is controlled by a tissue-specific and subset-selective multistep adhesion cascade.