Overproduction of Th2-specific chemokines in NC/Nga mice exhibiting atopic dermatitis-like lesions

Expression of CC chemokine receptor 4 (CCR4) mRNA in canine atopic skin lesion

CC chemokine receptor 4 (CCR4) is a G protein-coupled seven transmembrane receptor that is selectively expressed on Th2 cells and plays an important role in the trafficking of Th2 cells into inflammatory sites. In this study, a full-length canine CCR4 cDNA was cloned and characterized in order to examine the potential role of CCR4 in allergic responses that produce skin lesions in canine atopic dermatitis (AD). The canine CCR4 cDNA reported in this study contained an open reading frame of 1083 nucleotides encoding 360 amino acids. The predicted amino acid sequence of canine CCR4 showed 91.9, 85.3 and 84.5% similarity with those of the human, mouse and guinea pig counterparts, respectively. Expression of CCR4 mRNA was detected in various tissues including thymus, spleen, heart, small intestine and lymph node. Furthermore, it was found that CCR4 mRNA was preferentially expressed in lesional skin of dogs with AD, together with the mRNA of thymus and activation-regulated chemokine (TARC), which is a ligand for CCR4. The present study demonstrates that CCR4 contributes strongly to the immunopathogenesis of canine AD.

VIP and PACAP down-regulate CXCL10 (IP-10) and up-regulate CCL22 (MDC) in spleen cells

The immunoregulatory neuropeptides VIP and PACAP favor Th2-type immune responses. Antigen-stimulated Th2 cells produce VIP, VIP/PACAP induce Th2 cytokine responses, and promote the preferential survival of Th2 effectors. In this study, we investigate the effects of VIP/PACAP on two chemokines, i.e. CXCL10 (IP-10) acting on CXCR3 expressed on activated Th1 cells, and CCL22 (MDC) acting on CCR4 and 8 expressed on activated Th2 cells. VIP and PACAP down-regulate CXCL10, and up-regulate CCL22 in vivo and in vitro. The effects on the two chemokines appear to be different in mechanistic terms. The fact that VIP/PACAP might promote the directed migration of Th2 cells adds a new dimension to their participation in the Th2 auto-regulatory loop.

TGF-beta1-mediated regulation of thymus and activation-regulated chemokine (TARC/CCL17) synthesis and secretion by HaCaT cells co-stimulated with TNF-alpha and IFN-gamma

Thymus and activation-regulated chemokine (TARC/CCL17) contributes not only to the recruitment of leukocytes, but is also involved in immune disorders, such as atopic dermatitis (AD) and bronchial asthma. We have previously reported that the levels of TARC were high in patients with AD and that lesional epidermis were strongly immunoreactive for TARC. In this paper, the effects of transforming growth factor (TGF)-beta(1) on the expression of TARC/CCL17 were examined in HaCaT cells, a human keratinocytes (KCs) cell line, co-stimulated with TNF-alpha and IFN-gamma. We found that TGF-beta(1) down-regulated the TARC synthesis and secretion of HaCaT cells co-stimulated with TNF-alpha and IFN-gamma in a dose-dependent manner. TGF-beta(1) at a concentration of 10ng/ml maximally inhibited this secretion. Northern blot analysis showed a similar inhibitory effect of TGF-beta(1) on TARC mRNA expression by HaCaT cells. The TGF-beta(1)-induced down-regulation of TARC/CCL17 in HaCaT cells suggests that TGF-beta(1) might regulate the TARC-related inflammatory processes, which may be important for understanding the pathogenesis of allergic diseases.

Interleukin-13 induces thymus and activation-regulated chemokine (CCL17) in human peripheral blood mononuclear cells

BACKGROUND

In allergic inflammation involving allergic rhinitis, the predominance of Th(2) lymphocytes is one of the primary causal agents in promotion of the allergic condition. Thymus and activation-regulated chemokine (TARC/CCL17) is a recently identified chemokine that induces the development of Th(2) lymphocytes. One of the sources of TARC has been reported to be peripheral blood mononuclear cells (PBMCs).

OBJECTIVE

We investigated TARC production from PBMCs by the stimulation of specific antigens and Th(2) type cytokines.

METHOD

PBMCs were isolated from both allergic rhinitis patients and healthy volunteers. PBMCs were incubated with cytokine. TARC mRNA expression was examined by real time PCR methods and the amount of TARC production was examined by ELISA.

RESULTS

IL-13 was found to be the most potent inducer for TARC mRNA expression and protein production in PBMCs. Furthermore, tumour necrosis factor alpha and IL-13 synergistically induce TARC. The amount of TARC from allergic rhinitis patients was significantly larger than that from healthy volunteers. Moreover, TARC was induced by a specific antigen, and was 35% inhibited by an anti-IL-13 neutralizing antibody.

CONCLUSION

These results indicate that IL-13 is important in TARC mediated Th(2) lymphocytes infiltration in the nasal mucosa.

Differential regulation of thymus- and activation-regulated chemokine induced by IL-4, IL-13, TNF-alpha and IFN-gamma in human keratinocyte and fibroblast

The CC chemokine thymus- and activation-regulated chemokine (TARC/CCL17) acts on CC chemokine receptor 4 (CCR4), which is known to be selectively expressed in Th2 cells. In order to compare the regulatory profiles of TARC production by tumor necrosis factor-alpha (TNF-alpha), IFN-gamma, interleukin-4 (IL-4) and IL-13 in keratinocytes and fibroblasts, HaCaT cells, a human keratinocyte cell line, and NG1RGB cells, a human skin fibroblast cell line, were used. The expression of TARC protein was measured using enzyme-linked immunosorbent assay (ELISA), and the mRNA level was detected by reverse transcriptase polymerase chain reaction (RT-PCR). The spontaneous expression of TARC protein and mRNA levels were augmented by TNF-alpha and IFN-gamma and were inhibited by IL-4 and IL-13 in the keratinocytes. The fibroblasts expressed the TARC protein and mRNA only in the presence of IL-4+TNF-alpha or IL-13+TNF-alpha stimulation. IFN-gamma further enhanced the IL-4+TNF-alpha or IL-13+TNF-alpha-induced TARC production in the fibroblasts. Thus, TNF-alpha and IFN-gamma -induced TARC production was differentially regulated by IL-4 and IL-13 in human keratinocytes and fibroblasts.

T-helper 1, T-helper 2 and immunosuppressive cytokines in canine atopic dermatitis

Atopic dermatitis is a common inflammatory skin disease of humans and dogs. Human atopic dermatitis is associated with T-helper (Th) 2 type responses, although Th1 cytokines are present in chronic lesions. This study used semi-quantitative reverse transcriptase polymerase chain reactions to determine the expression of gene transcripts for immunosuppressive cytokines (transforming growth factor beta [TGFbeta] and interleukin [IL]-10), Th2 type cytokines (IL-4 and IL-6) and Th1 type cytokines (interferon gamma [IFNgamma], tumour necrosis factor alpha [TNFalpha], IL-2 and IL-12) in lesional atopic, non-lesional atopic and healthy canine skin. Canine atopic dermatitis was associated with over-expression of IL-4 mRNA and reduced transcription of TGFbeta compared to healthy skin (ANOVA, p<0.05). Higher levels of IFNgamma, TNFalpha and IL-2 mRNA were seen in lesional compared to non-lesional and healthy skin (p<0.05). There were no significant differences in IL-10, IL-6 or IL-12 transcription. This is the first report to demonstrate that canine atopic dermatitis is associated with over-production of IL-4 and under expression of TGFbeta.

Lesional expression of thymus and activation-regulated chemokine in canine atopic dermatitis

In this study, we investigated the mRNA expression of a chemokine, thymus and activation-regulated chemokine (TARC), and cytokines including IL-1beta, IL-4, IFN-gamma and TNF-alpha in skin samples obtained from both dogs with atopic dermatitis (AD) and healthy dogs. TARC mRNA was found to be selectively expressed in lesional skin of the dogs with AD, but not in non-lesional skin of the dogs with AD or the normal skin of the healthy dogs. The expression levels of IL-1beta, IFN-gamma and TNF-alpha in the lesional skin were also significantly higher than those in the non-lesional skin of the dogs with AD. However, IL-4 mRNA was not detected in any of the skin samples in this study. The present results suggest that TARC and inflammatory cytokines such as IL-1beta, IFN-gamma and TNF-alpha may play roles in the pathogenesis of canine AD as well as that of human AD.

Induction of macrophage-derived chemokine/CCL22 expression in experimental autoimmune encephalomyelitis and cultured microglia: implications for disease regulation

Macrophage-derived chemokine (MDC/CCL22) and its receptor CCR4 have been implicated in chronic inflammatory processes and in the homing of monocytes, Th2 cells and regulatory T-cell subsets. Here, we demonstrate that MDC and CCR4 mRNAs are expressed in the central nervous system (CNS) of mice developing relapsing-remitting and chronic-relapsing forms of experimental autoimmune encephalomyelitis (EAE). By immunohistochemistry, we show that MDC is produced by CNS-infiltrating leukocytes and intraparenchymal microglia, whereas CCR4 is expressed on some invading leukocytes. Upon in vitro activation, mouse microglia express MDC transcripts and secrete bioactive MDC that induces chemotaxis of Th2, but not Th1 cells. We suggest that MDC produced by microglia could regulate Th1-mediated CNS inflammation by facilitating the homing of Th2 and, possibly, regulatory T cells into the lesion site.

Quantitative differences in chemokine receptor engagement generate diversity in integrin-dependent lymphocyte adhesion

Chemokines control the specificity of lymphocyte homing. Numerous chemokines have been identified but the significance of redundancy in chemokine networks is unexplained. Here we investigated the biological significance of distinct chemokines binding to the same receptor. Among CCR4 ligands, skin vessels endothelial cells present C-C chemokine ligand (CCL) 17 but not CCL22 consistent with CCL17 involvement in T lymphocyte arrest on endothelial cells. However, CCL22 is much more powerful than CCL17 in the induction of rapid integrin-dependent T cell adhesion on VCAM-1 under conditions of physiological flow. The dominance of CCL22 over CCL17 extends to other CCR4-mediated phenomena such as receptor desensitization and internalization and correlates with the peculiar kinetics of CCR4 engagement by the two ligands. A similar phenomenological pattern is also shown for CXC chemokine ligand 9 and CXC chemokine ligand 11, which share binding to CXCR3. Our analysis shows how quantitative variations in chemokine receptor expression level and ligand engagement may alter the selectivity of integrin-dependent lymphocyte adhesive responses, suggesting a mechanism by which chemokine networks may either generate or break the specificity of lymphocyte subset recruitment.

Plasma concentration of thymus and activation-regulated chemokine is elevated in childhood asthma

BACKGROUND

Thymus and activation-regulated chemokine (TARC) is responsible for the trafficking of T(H)2 lymphocytes into sites of allergic inflammation. Serum TARC levels correlate with the severity of atopic dermatitis. The relationship between this marker and the occurrence and severity of asthma has not been evaluated.

OBJECTIVE

We tested whether plasma TARC level is a useful marker for asthma and atopy in children.

METHODS

Plasma total IgE levels were measured by means of microparticle immunoassay, and specific IgE levels to common aeroallergens were measured by using a fluorescent enzyme immunoassay. We used a sandwich enzyme immunoassay to measure plasma TARC concentrations.

RESULTS

Sixty asthmatic children and 28 age- and sex-matched control subjects were recruited, with mean logarithmic plasma total IgE levels of 2.66 +/- 0.60 kIU/L and 1.74 +/- 0.58 kIU/L, respectively (P <.0001). The median plasma TARC concentration was higher in asthmatic patients without inhaled corticosteroid treatment (131.0 pg/mL) compared with those seen in steroid-treated patients (97.5 pg/mL) and control subjects (76.0 pg/mL; P =.01 and P <.0001, respectively). Plasma TARC concentration was found to correlate with total IgE level in plasma (r = 0.219, P =.04). This marker was also increased in subjects who were sensitized to cat allergen (P =.001) but not in subjects sensitized to other aeroallergens. Disease severity score, FEV(1) value, and atopy were not associated with increased plasma TARC levels.

CONCLUSION

Our results suggest that plasma TARC concentrations are elevated in childhood asthma. This marker is also linked to plasma total IgE levels and cat allergen sensitization.

Evaluation of human thymus and activation-regulated chemokine concentrations in blood using a new sandwich ELISA based on monoclonal antibodies

BACKGROUND

CC chemokine TARC (thymus and activation-regulated chemokine), a potent chemoattractant for Th2 lymphocytes, is thought to play important roles in inflammatory diseases. We developed a new sensitive enzyme-linked immunoassay (ELISA) for human TARC (hTARC) to accurately measure and evaluate its concentrations in blood.

METHODS

An ELISA was developed using two established monoclonal antibodies against hTARC. Using this assay, we observed changes of hTARC concentrations in serum and plasma obtained from individual subjects. Improvements to the assay were made to allow use for the clinical evaluation of samples from atopic dermatitis (AD).

RESULTS

The lower detection limit of the ELISA was 1.4 pg/ml for a 25 microl sample volume. Other assay characteristics were enough to satisfactorily measure hTARC in biological fluids. This ELISA revealed that changes in serum and plasma concentrations were related to sample handling before separation from blood. With appropriate sample preparation, significant increases of hTARC were observed in patients with AD in comparison with normal subjects.

CONCLUSIONS

Appropriate sample preparation is important for clinical studies on hTARC. Accurate measurement using our ELISA method offers a suitable clinical index for evaluating the severity of allergic diseases of Th2-dominant disorders, such as AD.

Airway hyperresponsiveness, but not airway remodeling, is attenuated during chronic pulmonary allergic responses to Aspergillus in CCR4-/- mice

The role of CC chemokine receptor 4 (CCR4) during the development and maintenance of Th2-type allergic airway disease is controversial. In this study, we examined the role of CCR4 in the chronic allergic airway response to live Aspergillus fumigatus spores, or conidia, in A. fumigatus-sensitized mice. After the conidia challenge, mice lacking CCR4 (CCR4-/- mice) exhibited significantly increased numbers of airway neutrophils and macrophages, and conidia were more rapidly eliminated from these mice compared with control CCR4 wild-type (CCR4+/+) mice. Significant airway hyperresponsiveness to intravenous methacholine was observed at day 3 in CCR4-/- mice, whereas at days 7 and 30, airway hyperresponsiveness was attenuated in these mice compared with control mice. A major reduction in peribronchial and airway eosinophilia was observed in CCR4-/- mice at all times after conidia challenge in contrast to CCR4+/+ mice. Further, whole lung levels of interleukin (IL) 4 and IL-5 were significantly increased in CCR4-/- mice at day 3, whereas these Th2 cytokines and IL-13 were significantly decreased at day 30 in CCR4-/- mice compared with their wild-type counterparts. Peribronchial fibrosis and goblet cell hyperplasia were similar in both groups of mice throughout the course of this model. In summary, CCR4 modulates both innate and acquired immune responses associated with chronic fungal asthma.

A Th2 chemokine, TARC, produced by trophoblasts and endometrial gland cells, regulates the infiltration of CCR4+ T lymphocytes into human decidua at early pregnancy

PROBLEM

A chemokine receptor, CCR4 preferentially expressed on type 2 helper T (Th2-type) cells, and its ligand, thymus and activation regulated chemokine--(TARC/CCL)--play important roles in the recruitment of Th2-type cells. We examined the distribution of CCR4 expressing CD4+ and CD8+-T cells in human decidua at early pregnancy, and localized TARC in the decidual tissue and chorionic tissue.

METHOD OF STUDY

Decidual tissue was obtained by legal abortion. The percentages of CCR4 expressing CD4+ and CD8+-T cells were analyzed by flow cytometry. Localization of TARC protein was evaluated by immunofluorescence staining. The expression of TARC mRNA in the choriocarcinoma cell line and endometrial cell line was analyzed by reverse transcriptase polymerase chain reaction (RT-PCR).

RESULT

The percentages of CCR4+ cells in CD4+-T cells and CD8+-T cells were significantly increased in human early pregnancy decidua compared with those in peripheral blood. An another marker of human Th2 and Tc2 cells, CRTH2 molecules was also expressed on CCR4+ CD4+-T cells and CCR4+ CD8+-T cells. In addition, we found that trophoblasts, uterine epithelial cells and endometrial gland cells produce TARC by immunohistochemical staining and the RT-PCR method.

CONCLUSION

Our findings imply that TARC secreted in decidua mediates the infiltration of CCR4+ T-cell migration into the fetomaternal interface, decidua, resulting in the maintenance of pregnancy.

Presence of high contents of thymus and activation-regulated chemokine in platelets and elevated plasma levels of thymus and activation-regulated chemokine and macrophage-derived chemokine in patients with atopic dermatitis

BACKGROUND

T(H)2 cells and eosinophils selectively express CC chemokine receptor 4 and CCR3, respectively, and their chemokine ligands are likely to play important roles in the pathogenesis of atopic dermatitis (AD).

OBJECTIVE

The purpose of this study was to demonstrate the presence of thymus and activation-regulated chemokine (TARC) in platelets and its release during clotting and to evaluate the circulating levels of TARC, macrophage-derived chemokine (MDC), and eotaxin in control subjects and patients with AD.

METHODS

We compared plasma and serum contents of TARC, MDC, and eotaxin. We measured TARC contents in platelet lysates. We analyzed the correlation of plasma levels of TARC, MDC, and eotaxin with various clinicolaboratory parameters in patients with AD.

RESULTS

Serum contents of TARC rapidly increased during clotting, whereas those of MDC and eotaxin increased only slightly. We demonstrated that platelets contained TARC, and its levels were dramatically elevated in patients with AD. Platelets also released TARC on stimulation with thrombin. We therefore evaluated circulating levels of these chemokines in control subjects and patients with AD by using plasma samples. Plasma TARC levels were significantly increased in patients with AD (P <.0001) and showed significant correlations with severity scoring of atopic dermatitis (SCORAD) index (r = 0.665, P <.00001), serum lactate dehydrogenese levels (r = 0.696, P =.00001), eosinophil counts (r = 0.381, P =.007), and platelet counts (r = 0.562, P <.0001). Similarly, plasma MDC levels were significantly increased in patients with AD (P <.0001) and showed significant correlations with SCORAD index (r = 0.727, P <.0001), serum lactate dehydrogenese levels (r = 0.861, P <.0001), eosinophil counts (r = 0.505, P =.005), and platelet counts (r = 0.370, P =.01). On treatment, plasma TARC and MDC levels were dramatically decreased in accordance with improved SCORAD scores (P =.0012 and P =.0007, respectively). On the other hand, plasma eotaxin levels did not show any significant increase or correlation with any of the clinical parameters in patients with AD.

CONCLUSION

Platelets from patients with AD contain high levels of TARC. Thus platelets might play an important role in AD pathogenesis by releasing T(H)2-attracting TARC on activation. Furthermore, circulating levels of TARC and MDC, but not those of eotaxin, correlate well with the disease activity of AD.

Macrophage-derived chemokine gene transfer results in tumor regression in murine lung carcinoma model through efficient induction of antitumor immunity

Chemokine gene transfer represents a promising approach in the treatment of malignancies. Macrophage-derived chemokine (MDC) (CCL22) belongs to the CC chemokine family and is a strong chemoattractant for dendritic cells (DC), NK cells and T cells. Using adenoviral vectors, human MDC gene was transferred in vivo to investigate its efficacy to induce an antitumor response and to determine the immunologic mechanisms involved. We observed that intratumoral injection of recombinant adenovirus encoding human MDC (AdMDC) resulted in marked tumor regression in a murine model with pre-established subcutaneous 3LL lung carcinoma and induced significant CTL activity. The antitumor response was demonstrated to be CD4+ T cell- and CD8+ T cell-dependent. Administration of AdMDC induced chemoattraction of DC to the tumor site, facilitated DC migration to draining lymph nodes or spleen, and finally activated DC to produce high levels of IL-12. Furthermore, a significant increase of IL-4 production within the tumors was observed early after the AdMDC administration and was followed by the increase of IL-12 and IL-2 production. The levels of IL-2, IL-12 and IFN-gamma in serum, lymph nodes and spleen were also found to be higher in mice treated with AdMDC as compared with that in AdLacZ- or PBS-treated mice. The antitumor response induced by AdMDC was markedly impaired in IL-4 knockout mice, suggesting an important role of IL-4 in the induction of antitumor immunity by MDC. These results suggest that MDC gene transfer might elicit significant antitumor effects through efficient induction of antitumor immunity and might be of therapeutic potentials for cancer.

Cytokines and chemoattractants in allergic inflammation

It is now generally accepted type 2 T helper (Th2) cytokines and some chemoattractants play an essential role in the pathogenesis of the allergic inflammation. The effects of Th2 cytokines, such as interleukin (IL)-4, IL-5, IL-9, and IL-13, account for virtually all the pathophysiological manifestations of allergy and asthma. Moreover, both Th2 cells and the effector cells usually present in the areas of allergic inflammation (basophils, mast cells, and eosinophils) express chemoattractant receptors, such as CCR3, CCR4, CCR8 and CRTH2. Therefore, interactions of eotaxin(s), eotaxin/CCL11, RANTES/CCL5, and MCP-1/CCL2, MCP-2/CCL8, MCP-3/CCL7, MCP-4/CCL13 with CCR3 are responsible for the recruitment of basophils, eosinophils and mast cells, whereas interactions of CCR4 with MDC/CCL22 or TARC/CCL17, CCR8 with I-309/CCL1, and CRTH2 with prostaglandin D(2) play a critical role in the allergen-induced recruitment of Th2 cells in the target tissues of allergic inflammation. The demonstration that Th2-polarized responses against allergens represent the triggering event for the development of allergic diseases, together with the recognition that some chemoattractants are responsible for the recruitment of both Th2 cells and other effector cells of allergic inflammation, can provide the conceptual basis for the development of new therapeutic strategies in allergic conditions.

Expression of Th1, Th2 and immunosuppressive cytokine gene transcripts in canine atopic dermatitis

BACKGROUND

Atopic dermatitis is a common inflammatory skin disease of humans and dogs. Human atopic dermatitis is associated with Th2-type responses, although Th1 cytokines can be identified in chronic lesions. In contrast, tolerance to environmental allergens in healthy individuals is mediated by regulatory T cells.

OBJECTIVE

This study examined the expression of the immunosuppressive cytokines TGF-beta and IL-10, the Th2-type cytokines IL-4 and IL-6, and the Th1-type cytokines IFN-gamma, TNF-alpha, IL-2, IL-12p35 and IL-12p40, in canine atopic dermatitis.

MATERIALS AND METHODS

RNA was isolated from lesional atopic, non-lesional atopic and healthy canine skin samples. Semi-quantitative reverse transcriptase polymerase chain reactions (RT-PCRs) were carried out using specific primers and one-way analyses of variance used to compare cytokine expression in each group.

RESULTS

Canine atopic dermatitis was associated with over-expression of IL-4 mRNA and reduced transcription of TGF-beta compared with healthy skin (P < 0.05). Higher levels of IFN-gamma, TNF-alpha and IL-2 mRNA were seen in lesional compared with non-lesional and healthy skin (P < 0.05). There were no significant differences in IL-10, IL-6, IL-12p35 or IL-12p40 transcription between the three groups.

CONCLUSIONS

This is the first report to demonstrate that canine atopic dermatitis is associated with over-production of IL-4. Clinical tolerance in healthy individuals appears to be associated with TGF-beta, although it is unclear if this reflects an active mechanism or simply non-responsiveness of the immune system. Th1 cytokines may be induced by subsequent self-trauma and secondary infections in atopic skin. We believe that these results better characterize spontaneously occurring canine atopic dermatitis. We further propose that this should be investigated as a possible animal model of human atopic dermatitis.

Lipoteichoic acid from Staphylococcus aureus induces Th2-prone dermatitis in mice sensitized percutaneously with an allergen

BACKGROUND

We found previously that lipoteichoic acid (LTA) from Staphylococcus aureus has the ability to induce Th2 cytokine production by peripheral blood mononuclear cells (PBMC) from patients with atopic dermatitis (AD). However, it is not known whether LTA can induce a Th2-dominant cytokine response in the skin of AD patients.

OBJECTIVE

The purpose of this study was to determine the effects of LTA in mice sensitized percutaneously with a house dust mite antigen (MA) through barrier-disrupted skin, as an experimental animal model of AD.

METHODS

Mice were sensitized with MA by a single topical application to barrier-disrupted abdominal skin. Seven days after the sensitization, the mice were challenged on the dorsal skin by LTA to elicit localized skin inflammation. The cytokine response in the dorsal skin was investigated by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistological analysis. The infiltration of inflammatory cells in the skin was also observed by histological staining.

RESULTS

Injection of LTA into the dorsal skin of MA-sensitized mice, which show a Th2-dominant cytokine response against the homologous antigen, increased the expression of mRNA for IFN-gamma, IL-4 and IL-5, but not IL-2. Immunohistological analysis demonstrated that levels of IFN-gamma, IL-4 and IL-5 transcripts corresponded with those of protein synthesis. In addition, the dorsal skin of MA-sensitized mice challenged with LTA showed significantly increased numbers of neutrophils, eosinophils, mononuclear cells and mast cells compared with control mice challenged with LTA.

CONCLUSION

These results suggest that LTA has the ability to induce localized Th2-prone dermatitis in an allergen-independent manner in the skin of AD patients and may explain the role of colonization with S. aureus in AD patients.

Peripheral blood mononuclear cells from IgE- and non-IgE-associated allergic atopic eczema/dermatitis syndrome (AEDS) demonstrate increased capacity of generating interleukin-13 but differ in their potential of synthesizing interferon-gamma

BACKGROUND

A subgroup of patients with allergic atopic eczema/dermatitis syndrome (AEDS) are known to have normal total and specific IgE levels and negative skin prick tests towards common environmental allergens. This form of the disease has been termed non-IgE-associated allergic AEDS. Although allergic mechanisms appear to be important, the pathogenesis of both IgE- and non-IgE-associated forms of the disease is unknown.

METHODS

We have compared the cytokine production pattern of peripheral blood mononuclear cells (PBMC) from IgE-associated AEDS, non-IgE-associated AEDS, and normal control individuals. PBMC were stimulated with anti-CD3 and/or anti-CD28 monoclonal antibodies (mAb) and cytokine production was measured by immunoassays in supernatants of 24-h cultures.

RESULTS

Compared to healthy subjects and non-IgE-associated AEDS patients, stimulated PBMC from IgE-associated AEDS patients produced less interferon (IFN)-gamma. However, stimulated PBMC from both IgE-associated AEDS and non-IgE-associated AEDS patients produced more interleukin (IL)-13 than PBMC from control individuals. Moreover, IL-5 production was significantly increased in non-IgE-associated AEDS but not in IgE-associated AEDS patients.

CONCLUSIONS

The underlying mechanism leading to increased differentiation of T helper (Th) 2 cells may involve a deficient capacity in producing IFN-gamma in IgE-associated AEDS but not in non-IgE-associated AEDS patients. IL-13 may be a key cytokine in the pathogenesis of both allergic forms of AEDS.

Resident skin-specific gammadelta T cells provide local, nonredundant regulation of cutaneous inflammation

The function of the intraepithelial lymphocyte (IEL) network of T cell receptor (TCR) gammadelta(+) (Vgamma5(+)) dendritic epidermal T cells (DETC) was evaluated by examining several mouse strains genetically deficient in gammadelta T cells (delta(-/-) mice), and in delta(-/-) mice reconstituted with DETC or with different gammadelta cell subpopulations. NOD.delta(-/-) and FVB.delta(-/-) mice spontaneously developed localized, chronic dermatitis, whereas interestingly, the commonly used C57BL/6.delta(-/-) strain did not. Genetic analyses indicated a single autosomal recessive gene controlled the dermatitis susceptibility of NOD.delta(-/-) mice. Furthermore, allergic and irritant contact dermatitis reactions were exaggerated in FVB.delta(-/-), but not in C57BL/6.delta(-/-) mice. Neither spontaneous nor augmented irritant dermatitis was observed in FVB.beta(-/-) delta(-/-) mice lacking all T cells, indicating that alphabeta T cell-mediated inflammation is the target for gammadelta-mediated down-regulation. Reconstitution studies demonstrated that both spontaneous and augmented irritant dermatitis in FVB.delta(-/-) mice were down-regulated by Vgamma5(+) DETC, but not by epidermal T cells expressing other gammadelta TCRs. This study demonstrates that functional impairment at an epithelial interface can be specifically attributed to absence of the local TCR-gammadelta(+) IEL subset and suggests that systemic inflammatory reactions may more generally be subject to substantial regulation by local IELs.

The identification, characterization, and distribution of guinea pig CCR4 and epitope mapping of a blocking antibody

Th2 lymphocytes play a central role in the control and maintenance of allergic inflammation. The chemokine receptor CCR4 is preferentially expressed on the surface of Th2 lymphocytes polarised in vitro. However, CCR4 is found on the surface of a significant proportion of circulating memory T lymphocytes, some of which are capable of producing the Th1-associated cytokine interferon gamma. To investigate the function of CCR4 on guinea pig (gp) T lymphocytes, we identified the open-reading frame of gpCCR4, which encodes a 361-amino acid protein with 88 and 81% amino acid identity to human and murine CCR4 sequences, respectively. Cells transfected with gpCCR4 migrated toward the human and murine orthologues of the CCR4 ligands, macrophage-derived chemokine and thymus and activation-regulated chemokine. Surface expression of CCR4, using an anti-human CCR4 monoclonal antibody, 10E4, was detected on approximately 12% of guinea pig peripheral blood T helper cells, and CCR4(+) guinea pig thymocytes were detected in low numbers. However, CCR4(+) T helper cells constituted approximately 9% of the T lymphocyte population within the normal guinea pig lung and 52% of the guinea pig bronchoalveolar lavage fluid, which is consistent with a role for CCR4 in T lymphocyte development and trafficking through normal tissues. Subsequent analysis of chimeric chemokine receptors indicated that 10E4, a functional inhibitor of gpCCR4 responses, recognized the amino terminus of CCR4.

Frequent expression of CCR4 in adult T-cell leukemia and human T-cell leukemia virus type 1-transformed T cells

Chemokines and chemokine receptors play important roles in migration and tissue localization of various lymphocyte subsets. Here, we report the highly frequent expression of CCR4 in adult T-cell leukemia (ATL) and human T-cell leukemia virus type 1 (HTLV-1)-immortalized T cells. Flow cytometric analysis revealed that ATL and HTLV-1-immortalized T-cell lines consistently expressed CCR4. Inducible expression of HTLV-1 transcriptional activator tax in a human T-cell line Jurkat did not, however, up-regulate CCR4 mRNA. In vitro immortalization of peripheral blood T cells led to preferential outgrowth of CD4(+) T cells expressing CCR4. We further demonstrated highly frequent expression of CCR4 in fresh ATL cells by (1) reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of CCR4 expression in peripheral blood mononuclear cells (PBMCs) from patients with ATL and healthy controls; (2) flow cytometric analysis of CCR4-expressing cells in PBMCs from patients with ATL and healthy controls; (3) CCR4 staining of routine blood smears from patients with ATL; and (4) an efficient migration of fresh ATL cells to the CCR4 ligands, TARC/CCL17 and MDC/CCL22, in chemotaxis assays. Furthermore, we detected strong signals for CCR4, TARC, and MDC in ATL skin lesions by RT-PCR. Collectively, most ATL cases have apparently derived from CD4(+) T cells expressing CCR4. It is now known that circulating CCR4(+) T cells are mostly polarized to Th2 and also contain essentially all skin-seeking memory T cells. Thus, HTLV-1-infected CCR4(+) T cells may have growth advantages by deviating host immune responses to Th2. CCR4 expression may also account for frequent infiltration of ATL into tissues such as skin and lymph nodes.

Development of atopic dermatitis-like skin lesions in STAT6-deficient NC/Nga mice

Atopic dermatitis (AD) is a pruritic inflammatory skin disease characterized by elevation of plasma levels of total IgE, infiltration of mast cells and eosinophils, and the expression of cytokines by Th2 T cells. However, the role of Th2 cells in the pathogenesis of AD is not fully understood. In this study we examined the NC/Nga (NC) mouse model of AD and established STAT6-deficient (SATA6(-/-)) NC mice to investigate the relevance of IL-4-mediated immune responses. Surprisingly, these mice elicited AD-like skin lesions at equivalent frequency and time of onset compared with normal NC littermates. Histological features of the lesion in STAT6(-/-) NC mice fulfilled the criteria for the pathogenesis of AD, although these mice fail to produce IgE and Th2 cytokines. The lymph nodes proximal to the regions of skin that developed lesions exhibited massive enlargement elicited by the accumulation of activated IFN-gamma-secreting T cells. Moreover, caspase I, IL-18, IL-12, and IFN-gamma are found to be highly expressed at the skin lesion, occurring simultaneously with elevation of eotaxin 2 and CCR3 expression. Therefore, the Th2-mediated immune response is not necessary for the development of AD-like skin disease in NC mice. The skin microenvironment that favored IFN-gamma production tightly correlates with the skin disease in NC mice through the infiltration of eosinophils.

Transforming growth factor-beta1 suppresses atopic dermatitis-like skin lesions in NC/Nga mice

BACKGROUND

Atopic dermatitis is a chronic, relapsing inflammatory disorder characterized by pruritic and eczematous skin lesions. Transforming growth factor (TGF)-beta1 has been implicated in the suppression of inflammatory responses.

OBJECTIVE

The purpose of this study is to determine whether TGF-beta1 suppresses skin lesions in a mouse model of atopic dermatitis.

METHODS

We used the NC/Nga strain of mice as an in vivo model of atopic dermatitis. The effects of exogenous TGF-beta1 on atopic dermatitis-like skin lesions in NC/Nga mice were evaluated clinically, histologically and immunologically.

RESULTS

Subcutaneous injection of recombinant TGF-beta1 macroscopically suppressed eczematous skin lesions in NC/Nga mice associated with reduced serum immunoglobulin E (IgE) levels. Histological analysis showed that TGF-beta1 significantly inhibited the infiltration of inflammatory cells such as mast cells and eosinophils into the skin of NC/Nga mice. Spontaneous interferon (IFN)-gamma production from splenocytes of NC/Nga mice was down-regulated by the treatment with TGF-beta1 and neutralizing antibody against IFN-gamma inhibited skin lesions in NC/Nga mice. The inhibitory effect of TGF-beta1 on the skin lesions lasted at least 1 week after cessation of the treatment.

CONCLUSION

These findings indicate that TGF-beta1 suppressed atopic dermatitis-like skin lesions in NC/Nga mice at least in part through down-regulation of IFN-gamma. These results suggest that TGF-beta1 may have a therapeutic potential for atopic dermatitis.

Serum macrophage-derived chemokine (MDC) levels are closely related with the disease activity of atopic dermatitis

Atopic dermatitis (AD) is a chronic and relapsing inflammatory skin disease characterized by the predominant infiltration of T cells, eosinophils and macrophages in lesional skin. Recently, macrophage-derived chemokine (MDC)/CCL22, a CC chemokine, was identified as a selective chemoattractant for CC chemokine receptor 4 (CCR4)-expressing cells, in addition to thymus and activation-regulated chemokine (TARC). We have previously reported that serum TARC levels correlate with the severity of AD. In this report, we investigated the participation of MDC in AD. First, we measured serum MDC levels in 45 patients with AD, 25 patients with psoriasis vulgaris and 25 healthy controls. Serum MDC levels in AD patients were significantly higher than those in healthy controls and psoriasis patients. Furthermore, the increases in serum MDC levels in AD patients were greater in the severely affected group than in the moderate or mild groups. We compared serum MDC levels in 11 AD patients, before and after treatment, and observed a significant decrease after treatment. Moreover, the serum MDC levels significantly correlated with the Scoring AD (SCORAD) index, serum soluble (s) E-selectin levels, serum soluble interleukin-2 receptor (sIL-2R) levels, serum TARC levels and eosinophil numbers in peripheral blood. Our study strongly suggests that serum MDC levels have a notable correlation with disease activity and that MDC, as well as the CC chemokine TARC, may be involved in the pathogenesis of AD.

Antichemokine immunotherapy for allergic diseases

Chemokines have emerged as critical regulators of leukocyte function and as such represent attractive new targets for the therapy of allergic diseases. Recent studies have revealed important roles for the chemokine family in both the afferent and efferent limbs of the immune system, orchestrating and integrating innate and acquired immune responses. A subset of chemokines including eotaxin-1 (also called CCL11), eotaxin-2 (CCL24), eotaxin-3 (CCL26), MCP (monocyte chemoattractant protein)-3 (CCL7), MCP (monocyte chemoattractant protein)-4 (CCL13), TARC (thymus- and activation-regulated chemokine) (CCL17), and MDC (macrophage-derived chemokine) (CCL22) are highly expressed in allergic inflammation and are regulated by T helper type 2 cytokines. Receptors for these chemokines, including CCR3 (CC chemokine receptor 3), CCR4 (CC chemokine receptor 4) and CCR8 (CC chemokine receptor 8) are expressed on key leukocytes associated with allergic inflammation, such as T helper type 2 cells, eosinophils, mast cells and basophils, establishing a subset of chemokine/chemokine receptors potentially important in allergic inflammation. Recent data using inhibitory antibodies and chemokine antagonists support the concept that interfering with this subset of chemokines and their receptors represents a new approach to allergy immunotherapy.

Chemokines in immunity

Chemokines are a superfamily of small, heparin-binding cytokines that induce directed migration of various types of leukocytes through interactions with a group of seven-transmembrane G protein-coupled receptors. At present, over 40 members have been identified in humans. Until a few years ago, chemokines were mainly known as potent attractants for leukocytes such as neutrophils and monocytes, and were thus mostly regarded as the mediators of acute and chronic inflammatory responses. They had highly complex ligand-receptor relationships and their genes were regularly mapped on chromosomes 4 and 17 in humans. Recently, novel chemokines have been identified in rapid succession, mostly through application of bioinformatics on expressed sequence tag databases. A number of surprises have followed the identification of novel chemokines. They are constitutively expressed in lymphoid and other tissues with individually characteristic patterns. Most of them turned out to be highly specific for lymphocytes and dendritic cells. They have much simpler ligand-receptor relationships, and their genes are mapped to chromosomal loci different from the traditional chemokine gene clusters. Thus, the emerging chemokines are functionally and genetically quite different from the classical "inflammatory chemokines" and may be classified as "immune (system) chemokines" because of their profound importance in the genesis, homeostasis and function of the immune system. The emergence of immune chemokines has brought about a great deal of impact on the current immunological research, leading us to a better understanding on the fine traffic regulation of lymphocytes and dendritic cells. The immune chemokines and their receptors are also likely to be important future targets for therapeutic intervention of our immune responses.

Antigen-pulsed dendritic cells expressing macrophage-derived chemokine elicit Th2 responses and promote specific humoral immunity

Macrophage-derived chemokine (MDC) is a potent chemoattractant for antigen-specific T lymphocytes. We hypothesized that Adenovirus- (Ad-) transduced dendritic cells (DCs) overexpressing MDC would enhance the T cell-mediated humoral immune response specific for antigens presented by the DC. We challenged two strains of mice with lethal Pseudomonas aeruginosa infection 3 weeks after immunization with AdMDC-modified DCs pulsed with heat-killed P. aeruginosa. MDC-expressing DCs specifically attracted T lymphocytes and preserved typical DC surface phenotypes without growth factors in vitro. Mice immunized with AdMDC/Pseudomonas/DCs developed high levels of serum anti-Pseudomonas Ab's and were protected from a lethal respiratory challenge with Pseudomonas. The in vivo protective immunity required CD4(+) T cells, B cells, and IL-4, but not CD8(+) T cells and IL-12. AdMDC/DCs pulsed with Pseudomonas yielded significant but not absolute cross-protection against different strains of P. aeruginosa. Pseudomonas-pulsed AdMDC/DCs protected mice from Pseudomonas but not Escherichia coli and vice versa; this microbe-specific protection correlated with microbe-specific induction of CD4(+) T cell proliferation and IL-4 secretion. Based on these observations, AdMDC-modified DCs pulsed with a killed bacteria may be a useful approach to vaccination against infectious disorders.

Antigen-pulsed dendritic cells expressing macrophage-derived chemokine elicit Th2 responses and promote specific humoral immunity

Macrophage-derived chemokine (MDC) is a potent chemoattractant for antigen-specific T lymphocytes. We hypothesized that Adenovirus- (Ad-) transduced dendritic cells (DCs) overexpressing MDC would enhance the T cell-mediated humoral immune response specific for antigens presented by the DC. We challenged two strains of mice with lethal Pseudomonas aeruginosa infection 3 weeks after immunization with AdMDC-modified DCs pulsed with heat-killed P. aeruginosa. MDC-expressing DCs specifically attracted T lymphocytes and preserved typical DC surface phenotypes without growth factors in vitro. Mice immunized with AdMDC/Pseudomonas/DCs developed high levels of serum anti-Pseudomonas Ab's and were protected from a lethal respiratory challenge with Pseudomonas. The in vivo protective immunity required CD4(+) T cells, B cells, and IL-4, but not CD8(+) T cells and IL-12. AdMDC/DCs pulsed with Pseudomonas yielded significant but not absolute cross-protection against different strains of P. aeruginosa. Pseudomonas-pulsed AdMDC/DCs protected mice from Pseudomonas but not Escherichia coli and vice versa; this microbe-specific protection correlated with microbe-specific induction of CD4(+) T cell proliferation and IL-4 secretion. Based on these observations, AdMDC-modified DCs pulsed with a killed bacteria may be a useful approach to vaccination against infectious disorders.

Molecular cloning of canine thymus and activation-regulated chemokine (TARC) gene and its expression in various tissues

Thymus and activation-regulated chemokine (TARC) is known as a functional ligand for CC chemokine receptor 4 (CCR4), which is selectively expressed on Th2 lymphocytes and induces selective migration of the cells to allergic lesions. In this study, we cloned canine TARC cDNA from canine thymus by RT-PCR with rapid amplification of cDNA ends (RACE) method. The canine TARC clone contained a full-length open reading frame encoding 99 amino acids and included four cysteine residues characteristic to CC chemokine family. The canine TARC cDNA showed 77.5%, 67.4%, and 68.5% amino acid sequence similarity with human, mouse and rat homologues, respectively. Expression of TARC mRNA was detected not only in thymus but also in spleen, lymph node, lung and heart of the various normal dog tissues examined. TARC cDNA clone obtained in this study will be useful for further investigation on allergic diseases in dogs.

Protective roles of mast cells against enterobacterial infection are mediated by Toll-like receptor 4

Toll-like receptors (TLRs) are mammalian homologues of the Drosophila Toll receptors and are thought to have roles in innate recognition of bacteria. We demonstrated that TLR 2, 4, 6, and 8 but not TLR5 were expressed on mouse bone marrow-derived mast cells (BMMCs). Using BMMCs from the genetically TLR4-mutated strain C3H/HeJ, we demonstrated that functional TLR4 was required for a full responsiveness of BMMCs to produce inflammatory cytokines (IL-1beta, TNF-alpha, IL-6, and IL-13) by LPS stimulation. TLR4-mediated stimulation of mast cells by LPS was followed by activation of NF-kappaB but not by stress-activated protein kinase/c-Jun NH2-terminal kinase signaling. In addition, in the cecal ligation and puncture-induced acute septic peritonitis model, we demonstrated that genetically mast cell-deficient W/W(v) mice that were reconstituted with TLR4-mutated BMMCs had significantly higher mortality than W/W(v) mice reconstituted with TLR4-intact BMMCs. Higher mortality of TLR4-mutated BMMC-reconstituted W/W(v) mice was well correlated with defective neutrophil recruitment and production of proinflammatory cytokines in the peritoneal cavity. Taken together, these observations provide definitive evidence that mast cells play important roles in exerting the innate immunity by releasing inflammatory cytokines and recruitment of neutrophils after recognition of enterobacteria through TLR4 on mast cells.

CC chemokine receptor 4 expression on peripheral blood CD4+ T cells reflects disease activity of atopic dermatitis

Recent studies indicate that Th1 and Th2 cells differ in their chemokine receptor expression and their responsiveness to various chemokines. Therefore, selective Th2 cell recruitment in Th2-predominant inflammatory diseases such as atopic dermatitis may be under the influence of some chemokines. It is reported that CC chemokine receptor (CCR) 4 is selectively expressed on Th2 cells whereas CXC chemokine receptor (CXCR) 3 is selectively expressed on Th1 cells. In this study we examined CCR4 and CXCR3 expression on peripheral blood CD4+ and CD8+ T cells obtained from adult atopic dermatitis subjects, and compared the results with those from patients with psoriasis vulgaris and healthy controls. CCR4 was preferentially expressed on CD4+ T cells from atopic dermatitis subjects and CXCR3 was preferentially expressed on CD4+ T cells from psoriasis vulgaris subjects. This CCR4 expression was prominent especially in severe atopic dermatitis subjects. CCR4 expression on CD4+ T cells in severe atopic dermatitis subjects decreased on improvement of disease activity. CD25 was preferentially expressed on CCR4+CD4+ T cells but not on CXCR3+CD4+ T cells in atopic dermatitis subjects. Cutaneous lymphocyte-associated antigen was also preferentially expressed on CCR4+CD4+ T cells but not on CXCR3+CD4+ T cells in atopic dermatitis subjects. CD4+ T cells in atopic dermatitis skin lesions were predominantly CCR4+ cells. Taken together, this study strongly indicates that CCR4+CD4+ T cells reflect disease activity and suggests that CCR4 expression is important for T cell infiltration into atopic dermatitis lesions. Thus, CCR4 may be a possible target for therapy of atopic dermatitis in the future.

Transmission intensity determines lymphocyte responsiveness and cytokine bias in human lymphatic filariasis

Humans living in areas where filariasis is endemic vary greatly in their exposure to mosquito-borne infective third-stage larvae (L3) of these parasitic helminths. Because the intensity of exposure to Ags affects T cell differentiation and susceptibility to parasitic infections in murine models, we compared T cell and cytokine responses in 97 residents of two villages in Papua New Guinea, where transmission intensity of Wuchereria bancrofti differed by 63-fold (37 vs 2355 L3 per person per year). Residents of the high transmission village had 4- to 11-fold lower proliferation and IFN-gamma responses to filarial Ags, nonparasite Ag, and PHA by PBMC compared with the low transmission village (p < 0.01) even when subjects were matched for intensity of infection. In contrast, filarial Ag-driven IL-5 production was 5.5-fold greater (p < 0.001), and plasma IL-4 and TGF-beta levels were 4-fold and 34% higher, respectively, in residents of the high transmission village. IL-4 and IL-10 responses by PBMC differed little according to village, and increased production of the counterregulatory cytokines IL-10 or TGF-beta by PBMC did not correlate with weak proliferation and IFN-gamma responses. Plasma IL-5, IFN-gamma, and IL-10 levels were similar in the two villages. These data demonstrate that the intensity of exposure to L3 affects lymphocyte responsiveness and cytokine bias possibly by a mechanism that alters APC function.

Peripheral blood fibrocytes: differentiation pathway and migration to wound sites

Fibrocytes are a distinct population of blood-borne cells that display a unique cell surface phenotype (collagen I+/CD11b+/CD13+/CD34+/CD45RO+/MHC class II+/CD86+) and exhibit potent immunostimulatory activities. Circulating fibrocytes rapidly enter sites of tissue injury, suggesting an important role for these cells in wound repair. However, the regulatory processes that govern the differentiation of blood-borne fibrocytes and the mechanisms that underlie the migration of these cells to wound sites are currently not known. We report herein that ex vivo cultured fibrocytes can differentiate from a CD14+-enriched mononuclear cell population and that this process requires contact with T cells. Furthermore, we demonstrate that TGF-beta1 (1-10 ng/ml), an important fibrogenic and growth-regulating cytokine involved in wound healing, increases the differentiation and functional activity of cultured fibrocytes. Because fibrocytes home to sites of tissue injury, we examined the role of chemokine/chemokine receptor interactions in fibrocyte trafficking. We show that secondary lymphoid chemokine, a ligand of the CCR7 chemokine receptor, acts as a potent stimulus for fibrocyte chemotaxis in vitro and for the homing of injected fibrocytes to sites of cutaneous tissue injury in vivo. Finally, we demonstrate that differentiated, cultured fibrocytes express alpha smooth muscle actin and contract collagen gels in vitro, two characteristic features of wound-healing myofibroblasts. These data provide important insight into the control of fibrocyte differentiation and trafficking during tissue repair and significantly expand their potential role during wound healing.

Cytokine network and dysregulated apoptosis in atopic dermatitis

Activation and skin-selective homing of peripheral blood memory/effector T cells and effector functions in the skin represent sequential immunological events in the pathogenesis of atopic dermatitis (AD). T cells infiltrating the skin utilize the cutaneous lymphocyte-associated antigen (CLA) and other receptors to recognize and cross the vascular endothelium. In the peripheral blood of AD patients, both CD4+ and CD8 subsets of CLA+CD45RO+ T cells are in an activated state with high CD25, HLA-DR, and CD40-ligand expression. They express upregulated Fas and Fas-ligand and undergo activation-induced apoptosis. After homing to skin these T cells form dermal infiltrates which play a key role in the pathogenesis of the disease. Skin-infiltrating T cells in AD are protected from activation-induced cell death, although they express both Fas and Fas-ligand. They are protected from apoptosis by cytokines such as IL-2, IL-4, and IL-15 and extracellular matrix components such as fibronectin and transferrin. CLA+, skin-homing T cells may play a role in peripheral blood eosinophilia and hyper IgE production by high IL-5 and IL-13 expression, respectively. These T cells secrete IFN-gamma in the skin, which upregulates Fas on keratinocytes and renders them susceptible to apoptosis. Keratinocyte apoptosis is induced by Fas-ligand, either soluble or expressed on the surface of T cells, leading to eczema formation. Here we discuss the mechanisms of skin-selective T cell homing and activation, and emphasize the concept of dysregulated apoptosis of T cells, eosinophils, and keratinocytes as essential pathogenetic episodes in AD and other eczematous disorders.

III. Chemokines and other mediators, 8. Chemokines and their receptors in cell-mediated immune responses in the lung

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.

IL-10 augments the IFN-gamma and TNF-alpha induced TARC production in HaCaT cells: a possible mechanism in the inflammatory reaction of atopic dermatitis

The CC-chemokine TARC is known to be a ligand for the CCR4 receptor which in turn is known to be expressed selectively on the Th(2)-subset of lymphocytes. Atopic dermatitis is generally believed to be a Th(2)-type disease, and TARC has been shown to be expressed in the skin lesions of a murine model of AD. IL-10 is an interleukine generally known for its ability to inhibit cytokine production, however it has been found to be highly expressed in the skin from AD patients. We show in this report that IL-10 is able to augment the TARC inducing effects of TNFalpha and IFNgamma in HaCaT cells, a property that may be important in the determination of the composition of the cells of the inflammation in the skin of AD patients. In addition, we show that the IL10 agonist IT 9302, a nona-peptide from the carboxylic end of IL-10, has the same effect on TARC production from HaCaT cells.

The mechanism of a defective IFN-gamma response to bacterial toxins in an atopic dermatitis model, NC/Nga mice, and the therapeutic effect of IFN-gamma, IL-12, or IL-18 on dermatitis

NC/Nga (NC) mice raised under conventional conditions (Conv. NC mice) spontaneously develop dermatitis similar to human atopic dermatitis, whereas NC mice raised under the specific pathogen-free conditions do not develop dermatitis. In the present study, we show that the representative Th1 cytokine, IFN-gamma levels in the sera of NC mice, injected with either staphylococcal enterotoxin B or endotoxin (LPS), to be severalfold lower than those of normal mice. The low IFN-gamma response to staphylococcal enterotoxin B was correlated to the lack of regular Vbeta8(+) T cells and Vbeta8(+) NK T cells, and the low IFN-gamma response to LPS was correlated to an impaired IL-18 production of macrophages. The CD3-stimulated IL-4 production from liver and spleen T cells from Conv. NC mice in vitro was greatly augmented. The serum IL-4 levels of untreated Conv. NC mice also were higher than those of normal mice and specific pathogen-free NC mice. Treatment of Conv. NC mice either with IFN-gamma, IL-12, or IL-18 twice a week from 4 wk of age substantially inhibited the elevation of the serum IgE levels, serum IL-4 levels, and dermatitis, and IL-12 or IL-18 treatment also reduced the in vitro IL-4 production from CD3-stimulated liver T cells. The systemic deficiency in the Th1 response to bacterial stimulation thus leads to a Th2-dominant state and may induce an abnormal cellular immune response in the skin accompanied with an overproduction of IgE and a susceptibility to dermatitis in NC mice.

Atopic NC/Nga mice as a model for allergic asthma: severe allergic responses by single intranasal challenge with protein antigen

Since certain characters of allergic asthma are common with other allergic disorders like atopic dermatitis, the possible relationship in etiology is expected. Herein, we investigated whether NC/Nga mice, an inherent animal model for human atopic dermatitis, are inclined to allergic asthma. A single intranasal challenge of NC/Nga mice immunized with ovalbumin (OVA) resulted in an increase in plasma levels of OVA-specific IgE, and typical pathological aspects of allergic asthma characterized by infiltration of numerous eosinophils, mucus hyper production of bronchial epithelial cells. Moreover, airway hyperresponsiveness to inhaled acetylcholine and marked enhancement of airway resistance after the challenge were observed as compared to control BALB/c mice. Delayed expression of mRNA of eosinophil active chemokines, interleukin-5, eotaxin, macrophage inflammatory protein-1alpha in concert with eosinophilia was determined in the lung of NC/Nga mice. These results suggest that asthmatic responses developed in NC/Nga mice challenged with OVA are very similar to human allergic asthma, and that NC/Nga mice are a useful model to elucidate various aspects of allergic asthma.

Atopic NC/Nga mice as a model for allergic asthma: cytokine profiles and eosinophil productivity of bone marrow

In previous study, NC/Nga mice with experimentally induced asthma showed severe eosinophilia. To explore the mechanism, profiles of representative cytokines interleukin (IL)-4, IL-5, and interferon (IFN)-gamma were examined in bronchoalveolar lavage fluid. The level of only IFN-gamma was lower in NC/Nga mice than control BALB/c mice. Furthermore, bone marrow cell culture system under the presence of eosinopoietic cytokines, which induce the differentiation of progenitor cells into mature eosinophils, showed that a larger number of eosinophils differentiated from NC/Nga mice derived bone marrow cells than from control BALB/c mice. These results may imply the possibility that severe eosinophilia in the NC/Nga mice are attributable to lower production of IFN-gamma and higher eosinophil productivity of bone marrow cells.

Macrophage-derived chemokine (MDC/CCL22) and CCR4 are involved in the formation of T lymphocyte-dendritic cell clusters in human inflamed skin and secondary lymphoid tissue

Our previous study demonstrated formation of T cell-dendritic cell (DC) clusters in inflamed dermis of intraorally autotransplanted skin flaps. Such T cell-DC clusters are supposed to be important for close interactions between T cells and DCs including the specific antigen presentation. Here we show the involvement of the macrophage-derived chemokine (MDC/CCL22) and its specific receptor CC chemokine receptor 4 (CCR4) in the formation of T cell-DC clusters. Reverse transcriptase-polymerase chain reaction analysis revealed high levels of mRNA expression for MDC and CCR4 in inflamed skin and neck lymph nodes (LNs), but not in normal skin. Immunohistochemically, MDC(+) cells and CCR4(+) cells were mainly located within the T cell-DC clusters both in the dermis of inflamed skin and the T cell area of LNs. MDC(+) cells were identified to be DCs both in inflamed skin and LNs. The majority of CCR4(+) cells were CD4(+) T cells, accounting for approximately one-third of total CD4(+) T cells in the inflamed skin. Our data suggest that the MDC-CCR4 system plays an important role in the formation of T cell-DC clusters both in inflamed skin and LNs.

Regulated production of the T helper 2-type T-cell chemoattractant TARC by human bronchial epithelial cells in vitro and in human lung xenografts

The chemokine TARC is a ligand for the chemokine receptor CCR4 expressed on T helper (Th)2-type CD4 T cells. Allergic airway inflammation is characterized by a local increase in cells secreting Th2-type cytokines. We hypothesized that bronchial epithelial cells may be a source of chemokines known to chemoattract Th2 cells. Regulated TARC expression was studied using normal human bronchial epithelial cells and a human lung xenograft model. TARC expression was increased in normal human bronchial epithelial cells in response to tumor necrosis factor-alpha stimulation, and further upregulation of TARC was observed with interferon (IFN)-gamma but not interleukin (IL)-4 costimulation. TARC functions as a nuclear factor (NF)-kappa B target gene, as shown by the abrogation of TARC expression in response to proinflammatory stimuli when NF-kappa B activation is inhibited. In an in vivo model, minimal constitutive TARC expression was observed in human lung xenografts. Consistent with our findings in vitro, TARC messenger RNA (mRNA) expression was upregulated in the xenografts in response to IL-1, and costimulation with IFN-gamma but not IL-4 further increased TARC mRNA and protein expression. In addition, bronchoalveolar lavage fluid from asthmatic subjects after allergen challenge contained significantly increased levels of TARC, suggesting that TARC production by bronchial epithelial cells may play a role in the pathogenesis of allergic asthma.

What are the most promising strategies for the therapeutic immunomodulation of allergic diseases?

Specific immunotherapy and other immunomodulatory strategies have long been a stronghold in the management of allergic diseases. In particular, "immunodeviation-therapy" or "vaccination for allergies", i.e. the redirection of Th2-type immune responses towards a Th1-response pattern, has become an ever more popular concept. The present feature of CONTROVERSIES complements our previous discussion of atopy (Röcken et al., Exp Dermatol 7: 97--104, 1998), and is dedicated to a critical analysis of the general problems and limitations one faces with the main immunomodulatory strategies traditionally considered in this context. We also explore alternative approaches that appear promising in order to achieve both a more effective and/or a more specific immunotherapy of allergic diseases. Given that the mast cell remains a key protagonist in the pathogenesis of allergic diseases finally, this feature examines how innovative, more selectively mast cell-targeted strategies may be developed for the management of allergic diseases.

Thymus and activation-regulated chemokine in atopic dermatitis: Serum thymus and activation-regulated chemokine level is closely related with disease activity

BACKGROUND

Atopic dermatitis (AD) is a chronic and relapsing inflammatory skin disease characterized by the predominant infiltration of TH2-type cells in lesional skin. Thymus and activation-regulated chemokine (TARC/CCL17) is a chemokine that attracts CC chemokine receptor 4-positive (CCR4+) or CCR8+ cells.

OBJECTIVE

The purpose of this study was to investigate the participation of TARC in AD.

METHODS

We measured serum TARC levels in 40 patients with AD, 20 healthy control subjects, and 20 patients with psoriasis. We also examined disease activity by using SCORAD score; serum soluble E-selectin, soluble IL-2 receptor, IgE, and GM-CSF levels; and eosinophil numbers in peripheral blood, as well as correlations between TARC levels and these factors. The positivity of CCR4 of CD4+CD45RO+ cells in PBMCs was examined by using FACS analysis. Immunohistochemical staining of TARC and GM-CSF was performed in the lesional skin of patients with AD.

RESULTS

The serum TARC levels of patients with AD were significantly higher than those of healthy control subjects and patients with psoriasis. The serum TARC levels significantly correlated with eosinophil number (r = 0.61), SCORAD score (r = 0.60), and serum soluble E-selectin levels (r = 0.58) and weakly correlated with serum soluble IL-2 receptor levels (r = 0.34) in patients with AD. The TARC levels of patients with AD decreased after the treatment in accordance with the improvement of clinical symptoms. The CCR4 positivity of CD4+CD45RO+ cells in PBMCs of patients with AD was also higher than that of healthy control subjects. Immunohistochemical staining revealed that TARC was positive in keratinocytes in the epidermis and in vascular endothelial cells, T cells, and dendritic cells in the dermis.

CONCLUSION

Serum TARC levels are associated with disease activity of AD, and TARC may play an important role in the pathogenesis of AD.