TRPV1-positive sensory nerves and neuropeptides are involved in epidermal barrier repair after tape stripping in mice

BACKGROUND

The integumentary system of the skin serves as an exceptional protective barrier, with the stratum corneum situated at the forefront. This outermost layer is composed of keratinocytes that biosynthesize filaggrin (encoded by the gene Flg), a pivotal constituent in maintaining skin health. Nevertheless, the precise role of sensory nerves in restoration of the skin barrier after tape stripping-induced epidermal disruption, in contrast to the wound-healing process, remains a tantalizing enigma.

OBJECTIVE

This study aimed to elucidate the cryptic role of sensory nerves in repair of the epidermal barrier following tape stripping-induced disruption.

METHODS

Through the implementation of resiniferatoxin (RTX)-treated denervation mouse model, we investigated the kinetics of barrier repair after tape stripping and performed immunophenotyping and gene expression analysis in the skin or dorsal root ganglia (DRG) to identify potential neuropeptides. Furthermore, we assessed the functional impact of candidates on the recovery of murine keratinocytes and RTX-treated mice.

RESULTS

Ablation of TRPV1-positive sensory nerve attenuated skin barrier recovery and sustained subcutaneous inflammation, coupled with elevated IL-6 level in ear homogenates after tape stripping. Expression of the keratinocyte differentiation marker Flg in the ear skin of RTX-treated mice was decreased compared with that in control mice. Through neuropeptide screening, we found that the downregulation of Flg by IL-6 was counteracted by somatostatin or octreotide (a chemically stable somatostatin analog). Furthermore, RTX-treated mice given octreotide exhibited a partial improvement in barrier recovery after tape stripping.

CONCLUSION

Sensory neurons expressing TRPV1 play an indispensable role in restoring barrier function following epidermal injury. Our findings suggest the potential involvement of somatostatin in restoring epidermal repair after skin injury.

Circadian rhythm affects the magnitude of contact hypersensitivity response in mice

BACKGROUND

The circadian rhythm controls multiple biological processes, including immune responses; however, its impact on cutaneous adaptive immune response remains unclear.

METHODS

We used a well-established cutaneous type IV allergy model, contact hypersensitivity (CHS). We induced CHS using dinitrofluorobenzene (DNFB). Mice were sensitized and elicited with DNFB in the daytime or at night.

RESULTS

In mice, a nocturnally active animal, we found that ear swelling increased when mice were sensitized at night compared with in the daytime. In addition, cell proliferation and cytokine production in the draining lymph nodes (LNs) were promoted when sensitized at night. We hypothesized that these differences were due to the oscillation of leukocyte distribution in the body through the circadian production of adrenergic hormones. Administration of a β2-adrenergic receptor (β2AR) agonist salbutamol in the daytime decreased the number of immune cells in blood and increased the number of immune cells in LNs. In contrast, a β2AR antagonist ICI18551 administration at night increased the number of immune cells in blood and decreased the number of immune cells in LNs. Accordingly, the severity of CHS response was exacerbated by salbutamol administration in the daytime and attenuated by ICI18551 administration at night.

CONCLUSION

Our study demonstrated that the magnitude of adaptive CHS response depends on the circadian rhythm and this knowledge may improve the management of allergic contact dermatitis (ACD) in humans.

A phenotypic analysis of involucrin-mOVA mice following adoptive transfer of OVA-specific CD8+ T cells

To investigate the mechanism of autoimmunity and peripheral tolerance in the skin, several transgenic mouse strains expressing membrane-bound ovalbumin (mOVA) as an epidermal self-antigen under the control of keratinocyte-specific promotors, such as keratin 5 and keratin 14, were employed in combination with adoptive transfer of CD8⁺ T cells from OT-I mice (OT-I T cells) that recognize an ovalbumin-derived peptide. However, these strains showed bodyweight loss and required additional inflammatory stimuli, such as γ-irradiation and tape-stripping, to induce skin inflammation. In this study, we generated a mouse strain expressing mOVA under the control of human involucrin promoter (involucrin-mOVA mice). In contrast to previous strains, involucrin-mOVA mice spontaneously developed skin inflammation after the transfer of OT-I T cells in the absence of external stimuli without significant bodyweight loss. We focused on the skin infiltration process of OT-I T cells and found that transferred OT-I T cells accumulated around the hair follicles in the early phase of skin inflammation, and in the later phase, the skin inflammation spontaneously resolved despite the remaining OT-I T cells in the skin. Our involucrin-mOVA mice will provide a promising tool to investigate the pathogenesis and the tolerance mechanisms of cytotoxic skin autoimmunity.

CCL2‒CCR2 Signaling in the Skin Drives Surfactant-Induced Irritant Contact Dermatitis through IL-1β‒Mediated Neutrophil Accumulation

Surfactant-induced cumulative irritant contact dermatitis (ICD) is a common and clinically important skin disorder. CCL2 is known to mediate inflammation after tissue damage in various organs. Thus, we investigated whether and how CCL2 contributes to the development of murine cumulative ICD induced by a common surfactant, SDS. Wild-type mice treated topically with SDS for 6 consecutive days developed skin inflammation that recapitulated the features of human cumulative ICD, including barrier disruption, epidermal thickening, and neutrophil accumulation. CCL2 was upregulated in SDS-treated skin, and local CCL2 blockade attenuated SDS-induced ICD. SDS-induced ICD and neutrophil accumulation were also attenuated in mice deficient in CCR2, the receptor for CCL2. Neutrophil depletion alleviated SDS-induced ICD, suggesting that impaired neutrophil accumulation was responsible for the amelioration of ICD in CCR2-deficient mice. In RNA-sequencing analyses of SDS-treated skin, the expression levels of Il1b in Ccr2-deficient mice were highly downregulated compared with those in wild-type mice. Furthermore, the intradermal administration of IL-1β in the SDS-treated skin of CCR2-deficient mice restored the local accumulation of neutrophils and the development of ICD. Collectively, our results suggest that CCL2‒CCR2 signaling in the skin critically promotes the development of SDS-induced ICD by inducing IL-1β expression for neutrophil accumulation.

Pituitary adenylate cyclase-activating polypeptide promotes cutaneous dendritic cell functions in contact hypersensitivity

BACKGROUND

Sensory nerves regulate cutaneous local inflammation indirectly through induction of pruritus and directly by acting on local immune cells. The underlying mechanisms for how sensory nerves influence cutaneous acquired immune responses remain to be clarified.

OBJECTIVE

This study aimed to explore the effect of peripheral nerves on cutaneous immune cells in cutaneous acquired immune responses.

METHODS

We analyzed contact hypersensitivity (CHS) responses as a murine model of delayed-type hypersensitivity in absence or presence of resiniferatoxin-induced sensory nerve denervation. We conducted ear thickness measurements, flow cytometric analyses, and mRNA expression analyses in CHS.

RESULTS

CHS responses were attenuated in mice that were denervated during the sensitization phase of CHS. By screening neuropeptides, we found that pituitary adenylate cyclase-activating polypeptide (PACAP) mRNA expression was decreased in the dorsal root ganglia after denervation. Administration of PACAP restored attenuated CHS response in resiniferatoxin-treated mice, and pharmacological inhibition of PACAP suppressed CHS. Flow cytometric analysis of skin-draining lymph nodes showed that cutaneous dendritic cell migration and maturation were reduced in both denervated mice and PACAP antagonist-treated mice. The expression of chemokine receptors CCR7 and CXCR4 of dendritic cell s was enhanced by addition of PACAP in vitro.

CONCLUSION

These findings indicate that a neuropeptide PACAP promotes the development of CHS responses by inducing cutaneous dendritic cell functions during the sensitization phase.

Prolonged high-intensity exercise induces fluctuating immune responses to herpes simplex virus infection via glucocorticoids

BACKGROUND

Epidemiologic studies have yielded conflicting results regarding the influence of a single bout of prolonged high-intensity exercise on viral infection.

OBJECTIVE

We sought to learn whether prolonged high-intensity exercise either exacerbates or ameliorates herpes simplex virus type 2 (HSV-2) infection according to the interval between virus exposure and exercise.

METHODS

Mice were intravaginally infected with HSV-2 and exposed to run on the treadmill.

RESULTS

Prolonged high-intensity exercise 17 hours after infection impaired the clearance of HSV-2, while exercise 8 hours after infection enhanced the clearance of HSV-2. These impaired or enhanced immune responses were related to a transient decrease or increase in the number of blood-circulating plasmacytoid dendritic cells. Exercise-induced glucocorticoids transiently decreased the number of circulating plasmacytoid dendritic cells by facilitating their homing to the bone marrow via the CXCL12-CXCR4 axis, which led to their subsequent increase in the blood.

CONCLUSION

A single bout of prolonged high-intensity exercise can be either deleterious or beneficial to antiviral immunity.

High-fat diet induces a predisposition to follicular hyperkeratosis and neutrophilic folliculitis in mice

BACKGROUND

Neutrophilic folliculitis is an inflammatory condition of hair follicles. In some neutrophilic folliculitis, such as in patients with acne and hidradenitis suppurativa, follicular hyperkeratosis is also observed. Neutrophilic folliculitis is often induced and/or exacerbated by a high-fat diet (HFD). However, the molecular mechanisms by which an HFD affects neutrophilic folliculitis are not fully understood.

OBJECTIVE

Our aim was to elucidate how an HFD promotes the development of neutrophilic folliculitis.

METHODS

Mice were fed an HFD, and their skin was subjected to histologic, RNA sequencing, and imaging mass spectrometry analyses. To examine the effect of an HFD on neutrophil accumulation around the hair follicles, phorbol 12-myristate 13-acetate (PMA) was used as an irritant to the skin.

RESULTS

Histologic analysis revealed follicular hyperkeratosis in the skin of HFD-fed mice. RNA sequencing analysis showed that genes related to keratinization, especially in upper hair follicular keratinocytes, were significantly upregulated in HFD-fed mice. Application of PMA to the skin induced neutrophilic folliculitis in HFD-fed mice but not in mice fed a normal diet. Accumulation of neutrophils in the skin and around hair follicles was dependent on CXCR2 signaling, and CXCL1 (a CXCR2 ligand) was produced mainly by hair follicular keratinocytes. Imaging mass spectrometry analysis revealed an increase in fatty acids in the skin of HFD-fed mice. Application of these fatty acids to the skin induced follicular hyperkeratosis and caused PMA-induced neutrophilic folliculitis even in mice fed a normal diet.

CONCLUSION

An HFD can facilitate the development of neutrophilic folliculitis with the induction of hyperkeratosis of hair follicles and increased neutrophil infiltration around the hair follicles via CXCR2 signaling.

Essential role of CCL2-CCR2 axis in the pathogenesis of chronic irritant contact dermatitis

Chronic irritant contact dermatitis (ICD) including hand eczema is a common skin disorder caused by the repetitive exposure to irritants such as chemical detergents and organic solvents. Products including sodium dodecyl sulfate (SDS), such as soap or shampoo, are the leading cause of occupational ICD. Previous studies have shown that irritants cause epidermal damage which induce the production of proinflammatory mediators, followed by a dermal influx of inflammatory cells. However, the detailed immunological cascades occurring in the chronic ICD remains unclear.

Repeated application of SDS, onto murine ear skin induced ear swelling, accompanied by epidermal hyperplasia and barrier dysfunction. Dermal infiltration of neutrophils, eosinophils and monocytes were remarkable in the SDS-applied skin. Our observation described above was consistent with the features of human chronic ICD. Here, we found that CCR2 deficiency or blockade of CCL2, a major ligand for CCR2, significantly attenuated SDS-induced ear swelling as well as inflammatory cell accumulation. Among the differentially expressed genes, which were up-regulated by SDS application, genes related to cell interaction at the vascular wall were significantly affected by CCR2 deficiency. Further, we investigated whether CCR2 on radiosensitive cells or radioresistant cells is critical. Lethally irradiated CCR2−/− mice transplanted with CCR2+/+ bone marrow cells (BMC) exhibited impaired SDS-induced ICD, while CCR2+/+ mice transplanted with CCR2−/− did not.

Collectively, our data suggest that CCR2 expression by radioresistant cells plays an essential role in the pathogenesis of chronic ICD.

Percutaneous sensitization is limited by in situ inhibition of cutaneous dendritic cell migration through skin-resident regulatory T cells

BACKGROUND

Percutaneous sensitization is associated with various allergic diseases, including asthma and food allergies. However, the immunologic mechanisms underlying how the skin regulates percutaneous sensitization are still unclear.

OBJECTIVE

We aimed to investigate whether and how CD4⁺Foxp3⁺ regulatory T (Treg) cells residing in the skin regulate percutaneous sensitization in the skin.

METHODS

Selective reduction of numbers of cutaneous Treg cells was achieved by means of intradermal injection of diphtheria toxin into the ear skin of Foxp3^DTR mice, in which Treg cells specifically express the diphtheria toxin receptor fused with green fluorescent protein.

RESULTS

Thirty percent to 40% of cutaneous Treg cells were capable of IL-10 production in both mice and human subjects. Selective reduction of cutaneous Treg cells at the sensitization site promoted migration of antigen-bearing dendritic cells (DCs) to the draining lymph nodes (dLNs). Accordingly, sensitization through the skin with reduced numbers of Treg cells led to enhanced antigen-specific immune responses in the dLNs, including both effector T-cell differentiation and T cell-dependent B-cell responses, such as the development of germinal center B cells expressing IgG₁ and IgE. Furthermore, antigen-bearing cutaneous DC migration was enhanced in mice with IL-10 deficiency restricted to the cutaneous Treg cell compartment, suggesting an important role of cutaneous IL-10⁺ Treg cells in limiting percutaneous sensitization. Treg cells with a skin-homing phenotype in skin dLNs expressed high levels of IL-10, suggesting that they contribute to renewal and maintenance of the cutaneous IL-10⁺ Treg cell population.

CONCLUSION

Skin-resident Treg cells limit percutaneous sensitization by suppressing antigen-bearing DC migration through in situ IL-10 production.

Essential Roles of CCL2-CCR2 and C5a-C5aR1 Pathways in irritant Contact Dermatitis

Cutaneous immune response induced by epithelial cell stress induces represents the first line defense against pathogens. We have reported that basophils play a pivotal role in the skin inflammation caused by irritants. However, it has not been fully understood how they accumulate in the skin. Previous studies have shown that epithelial cell damage induces complement activation in organs such as the lung and the kidney, implicating a possible involvement of the complement activation in the immune response caused by epithelial cell stress in the skin. Thus, we investigated the mechanism of basophil recruitment to the skin focusing on the complement system.

Topical application of the surfactant sodium dodecyl sulfate (SDS) onto murine ears induced basophil-dependent skin inflammation. Among chemokines which were up-regulated by SDS application, we found that CCL2-CCR2 axis was critical for basophil recruitment to the skin. Here, CCR2 on basophils was dispensable and CCR2 on radioresistant cells was essential.

Finally, we evaluated the contribution of complement system to SDS-induced basophil recruitment to the skin. SDS application induced C3 and C5a production in the skin, suggesting a complement activation in the skin. We evaluated whether C3 and C5a are involved in SDS-induced basophil recruitment by using C3 deficient mice and C5a receptor 1 deficient mice. The result showed that C3 deficiency or C5aR1 deficiency significantly attenuated SDS-induced basophils accumulation. By contrast, SDS-induced CCL2 production in these mice was comparable to WT mice.

Collectively, our data suggest that both CCL2-CCR2 and C5a-C5aR pathways are essential to the SDS-induced innate immune response in the skin by modulating basophil recruitment.

Accumulation of exhausted CD8+ T cells in extramammary Paget's disease

Cancer immunotherapy has highlighted the clinical relevance of enhancing anti-tumor response of CD8+ T cells in several cancer types. Little is known, however, about the involvement of the immune system in extramammary Paget’s disease (EMPD). We examined the cytotoxicity and the effector functions of CD8+ T cells using paired samples of peripheral blood and tumors by flow cytometry. Expression levels of perforin, granzyme B, IFN-g, TNF-a, and IL-2 in CD8+ tumor-infiltrating lymphocytes (TILs) were significantly lower than those in CD8+ T cells of peripheral blood. Significantly higher expression of PD-1 was found in CD8+TILs than in CD8+ T cells of peripheral blood. A high number of CD8+ cells was significantly associated with poor overall survival (OS) adjusted with age, sex, and clinical stage (hazard ratio [HR] = 5.03, P = 0.045, 95% confidence interval [CI] 1.03–24.4). On the other hand, the number of PD-1+ cells was not associated with OS or disease-free survival (DFS). Moreover, we found that tumor cells produced immunosuppressive molecule indoleamine 2,3-dyoxygenae (IDO). In conclusion, CD8+ TILs displayed an exhausted phenotype in EMPD. IDO expression seemed more relevant in inducing CD8 exhaustion than PD-1 upregulation or PD-L1 expression by immune cells. Restoring the effector functions of CD8+ TILs could be an effective treatment strategy for advanced EMPD.

The epithelial immune microenvironment (EIME) in atopic dermatitis and psoriasis

The skin provides both a physical barrier and an immunologic barrier to external threats. The protective machinery of the skin has evolved to provide situation-specific responses to eliminate pathogens and to provide protection against physical dangers. Dysregulation of this machinery can give rise to the initiation and propagation of inflammatory loops in the epithelial microenvironment that result in inflammatory skin diseases in susceptible people. A defective barrier and microbial dysbiosis drive an interleukin 4 (IL-4) loop that underlies atopic dermatitis, while in psoriasis, disordered keratinocyte signaling and predisposition to type 17 responses drive a pathogenic IL-17 loop. Here we discuss the pathogenesis of atopic dermatitis and psoriasis in terms of the epithelial immune microenvironment-the microbiota, keratinocytes and sensory nerves-and the resulting inflammatory loops.

Epithelial TRAF6 drives IL-17-mediated psoriatic inflammation

Epithelial cells are the first line of defense against external dangers, and contribute to induction of adaptive immunity including Th17 responses. However, it is unclear whether specific epithelial signaling pathways are essential for the development of robust IL-17-mediated immune responses. In mice, the development of psoriatic inflammation induced by imiquimod required keratinocyte TRAF6. Conditional deletion of TRAF6 in keratinocytes abrogated dendritic cell activation, IL-23 production, and IL-17 production by γδ T cells at the imiquimod-treated sites. In contrast, hapten-induced contact hypersensitivity and papain-induced IgE production were not affected by loss of TRAF6. Loss of psoriatic inflammation was not solely due to defective imiquimod sensing, as subcutaneous administration of IL-23 restored IL-17 production but did not reconstitute psoriatic pathology in the mutant animals. Thus, TRAF6 was required for the full development of IL-17-mediated inflammation. Therefore, epithelial TRAF6 signaling plays an essential role in both triggering and propagating IL-17-mediated psoriatic inflammation.

High fat diet exacerbates murine psoriatic dermatitis by increasing the number of IL-17-producing γδ T cells

Psoriasis is a common, chronic inflammatory skin disease characterized by epidermal hyperplasia via the IL-23/IL-17 axis. Various studies have indicated the association between obesity and psoriasis, however, the underlying mechanisms remains unclarified. To this end, we focused on high-fat diet (HFD) in this study, because HFD is suggested as a contributor to obesity, and HFD-fed mice exhibit exacerbated psoriatic dermatitis. Using murine imiquimod (IMQ)-induced psoriasis and HFD-induced obesity models, we have revealed a novel mechanism of HFD-induced exacerbation of psoriatic dermatitis. HFD-fed mice exhibited aggravated psoriatic dermatitis, which was accompanied with increased accumulation of IL-17A-producing Vγ4⁺ γδ T cells in the skin. HFD also induced the increase of Vγ4⁺ γδ T cells in other organs such as skin draining lymph nodes, which preceded the increase of them in the skin. In addition, HFD-fed mice displayed increased expression of several γδ T cell-recruiting chemokines in the skin. On the other hand, ob/ob mice, another model of murine obesity on normal diet, did not exhibit aggravated psoriatic dermatitis nor accumulation of γδ T cells in the dermis. These results indicate that HFD is a key element in exacerbation of IMQ-induced psoriatic dermatitis, and further raise the possibility of HFD as a factor that links obesity and psoriasis.

Inhibition of IL-17-committed T cells in a murine psoriasis model by a vitamin D analogue

BACKGROUND

A better understanding of the means by which topical vitamin D analogues exert their therapeutic effect on psoriasis is of theoretical and practical importance.

OBJECTIVE

We sought to clarify whether and how the topical vitamin D analogue calcipotriol (CAL) controls the IL-17A-mediated pathogenesis of murine psoriasis-like dermatitis in vivo.

METHODS

Psoriasis-like dermatitis was induced by the topical application of an imiquimod (IMQ)-containing cream on the murine ear for 4 to 6 consecutive days. For topical CAL treatment, mice were treated daily with CAL solution on the ear before IMQ application.

RESULTS

Mice treated topically with CAL exhibited much milder IMQ-induced psoriasis-like dermatitis compared with vehicle-treated mice, with impaired accumulation of IL-17A-committed T (T17) cells in the lesional skin. The IMQ-induced upregulation of Il12b and Il23a was marked in the epidermis and was abrogated by CAL application, suggesting CAL-mediated suppression of IL-23 expression. CAL inhibited Il12b and Il23a expression by Langerhans cells ex vivo stimulated with IMQ and CD40 cross-linking. Topical CAL also inhibited T17 cell expansion in the draining lymph nodes of IMQ-treated skin, implying a possible effect on T17 cell-mediated dermatitis at distant sites. In fact, topical CAL application on the IMQ-treated left ear resulted in amelioration of T17 cell accumulation and psoriasis-like dermatitis in the right ear subsequently treated with IMQ.

CONCLUSION

Topical CAL can exert its antipsoriatic effect on CAL-treated lesions and, concomitantly, distant lesions by attenuating the T17 cell accumulation in both CAL-treated lesions and draining lymph nodes.

Indispensable role of IL-10 in the development of antigen cross-presentation capacity of the cDC1 subset

The conventional type 1 dendritic cell (cDC1) is a distinct DC subset with specialized functions including cross-presentation of antigens to CD8 T cells and CD103 expression. cDC1s require GM-CSF signal for gaining their signature functions; however, the involvement of other cytokines remains unknown.

Here we found that cDC1s were normal in number but lacked CD103 expression in IL-10-deficient (Il10−/−) mice, suggesting that IL-10 has some effects on cDC1 function in vivo. Thus, next we assessed the CD8 T-cell priming capacity of cDC1s from Il10+/+ and Il10−/− mice by coculture with OT-I CD8+ T cells in the presence of ovalbumin in vitro. In contrast to Il10+/+ cDC1s, Il10−/− cDC1s failed to induce the expansion and IFN-γ production of OT-I cells. In addition, Il10−/− mice had a significantly lower number of memory CD8 T cells in the lymph nodes in the steady state. These results indicate that cDC1s in Il10−/− mice were defective in antigen cross-presentation. We also found that, whereas Flt3-ligand-induced DCs derived from Il10+/+ bone marrow cells upregulated CD103 expression by and CD8 T-cell cross-priming capacity of the cDC1-equivalent population in response to GM-CSF stimulation, Il10−/− bone marrow-derived DCs did not, suggesting that dysfunction of cDC1s in Il10−/− mice is likely due to unresponsiveness to GM-CSF. Finally, we found that mRNA expression of Csf2ra, which encodes GM-CSF receptor α-chain, was completely deficient in both cDC1s in Il10−/− mice and Il10−/− cDC1-equivalent bone marrow-derived DCs. Collectively, our data suggest that IL-10 critically controls the development of antigen cross-presentation capacity of cDC1s under homeostatic conditions, likely through regulating GM-CSF receptor expression.

Peripheral blood Th9 cells are a possible pharmacodynamic biomarker of nivolumab treatment efficacy in metastatic melanoma patients

Although nivolumab is associated with a significant improvement in overall survival and progression-free survival, only 20 to 40% of patients experience long-term benefit. It is therefore of great interest to identify a predictive marker of clinical benefit for nivolumab. To address this issue, the frequencies of CD4⁺ T cell subsets (Treg, Th1, Th2, Th9, Th17 and Th22), CD8⁺ T cells, and serum cytokine levels (IFNγ, IL-4, IL-9, IL-10, TGF-β) were assessed in 46 patients with melanoma. Eighteen patients responded to nivolumab, and the other 28 patients did not. An early increase in Th9 cell counts during the treatment with nivolumab was associated with an improved clinical response. Before the first nivolumab infusion, the responders displayed elevated serum concentrations of TGF-β compared to non-responders. Th9 induction by IL-4 and TGF-β was enhanced by PD-1/PD-L1 blockade in vitro. The role of IL-9 in disease progression was further assessed using a murine melanoma model. In vivo IL-9 blockade promoted melanoma progression in mice using an autochthonous mouse melanoma model, and the cytotoxic ability of murine melanoma-specific CD8⁺ T cells was enhanced in the presence of IL-9 in vitro. These findings suggest that Th9 cells, which produce IL-9, play an important role in the successful treatment of melanoma patients with nivolumab. Th9 cells therefore represent a valid biomarker to be further developed in the setting of anti-PD-1 therapy.

Resolvin E1 inhibits dendritic cell migration in the skin and attenuates contact hypersensitivity responses

Resolvin E1 (RvE1) is a lipid mediator derived from ω3 polyunsaturated fatty acids that exerts potent antiinflammatory roles in several murine models. The antiinflammatory mechanism of RvE1 in acquired immune responses has been attributed to attenuation of cytokine production by dendritic cells (DCs). In this study, we newly investigated the effect of RvE1 on DC motility using two-photon microscopy in a contact hypersensitivity (CHS) model and found that RvE1 impaired DC motility in the skin. In addition, RvE1 attenuated T cell priming in the draining lymph nodes and effector T cell activation in the skin, which led to the reduced skin inflammation in CHS. In contrast, leukotriene B4 (LTB4) induced actin filament reorganization in DCs and increased DC motility by activating Cdc42 and Rac1 via BLT1, which was abrogated by RvE1. Collectively, our results suggest that RvE1 attenuates cutaneous acquired immune responses by inhibiting cutaneous DC motility, possibly through LTB4-BLT1 signaling blockade.

The Janus kinase inhibitor JTE-052 improves skin barrier function through suppressing signal transducer and activator of transcription 3 signaling

BACKGROUND

Barrier disruption and the resulting continuous exposure to allergens are presumed to be responsible for the development of atopic dermatitis (AD). However, the mechanism through which skin barrier function is disrupted in patients with AD remains unclear.

OBJECTIVES

Taking into account the fact that the TH2 milieu impairs keratinocyte terminal differentiation, we sought to clarify our hypothesis that the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway plays a critical role in skin barrier function and can be a therapeutic target for AD.

METHODS

We analyzed the mechanism of keratinocyte differentiation using a microarray and small interfering RNA targeting STATs. We studied the effect of the JAK inhibitor JTE-052 on keratinocyte differentiation using the human skin equivalent model and normal human epidermal keratinocytes. We applied topical JAK inhibitor onto NC/Nga mice, dry skin model mice, and human skin grafted to immunocompromised mice.

RESULTS

IL-4 and IL-13 downregulated genes involved in keratinocyte differentiation. STAT3 and STAT6 are involved in keratinocyte differentiation and chemokine production by keratinocytes, respectively. Topical application of the JAK inhibitor suppressed STAT3 activation and improved skin barrier function, permitting increases in levels of terminal differentiation proteins, such as filaggrin, and natural moisturizing factors in models of AD and dry skin and in human skin.

CONCLUSION

STAT3 signaling is a key element that regulates keratinocyte differentiation. The JAK inhibitor can be a new therapeutic tool for the treatment of disrupted barrier function in patients with AD.

Basophils regulate the recruitment of eosinophils in a murine model of irritant contact dermatitis

BACKGROUND

Although eosinophils have been detected in several human skin diseases in the vicinity of basophils, how eosinophils infiltrate the skin and the role of eosinophils in the development of skin inflammation have yet to be examined.

OBJECTIVE

Using murine irritant contact dermatitis (ICD) as a model, we sought to clarify the roles of eosinophils in ICD and the underlying mechanism of eosinophil infiltration of the skin.

METHODS

We induced croton oil-induced ICD in eosinophil-deficient ΔdblGATA mice with or without a reactive oxygen species (ROS) inhibitor. We performed cocultivation with fibroblasts and bone marrow-derived basophils and evaluated eosinophil migration using a chemotaxis assay.

RESULTS

ICD responses were significantly attenuated in the absence of eosinophils or by treatment with the ROS inhibitor. ROS was produced abundantly by eosinophils, and both basophils and eosinophils were detected in human and murine ICD skin lesions. In coculture experiments, basophils attracted eosinophils, especially in the presence of fibroblasts. Moreover, basophils produced IL-4 and TNF-α in contact with fibroblasts and promoted the expression of eotaxin/CCL11 from fibroblasts in vitro.

CONCLUSION

Eosinophils mediated the development of murine ICD, possibly through ROS production. Recruitment of eosinophils into the skin was induced by basophils in cooperation with fibroblasts. Our findings introduce the novel concept that basophils promote the recruitment of eosinophils into the skin through fibroblasts in the development of skin inflammation.

Basophils are required for the induction of Th2 immunity to haptens and peptide antigens

The relative contributions of basophils and dendritic cells in Th2 skewing to foreign antigen exposure remain unclear. Here we report the ability of basophils to induce Th2 polarization upon epicutaneous sensitization with different antigens using basophil conditionally depleted Bas TRECK transgenic mice. Basophils are responsible for Th2 skewing to haptens and peptide antigens, but not protein antigens in vivo. Consistent with this, basophils cannot take up or process ovalbumin protein in significant quantities, but present ovalbumin peptide to T cells for Th2 differentiation via major histocompatibility complex class II. Intriguingly, basophils promote Th2 skewing upon ovalbumin protein exposure in the presence of dendritic cells. Taken together, our results suggest that basophils alone are able to induce Th2 skewing with haptens and peptide antigens but require dendritic cells for the induction of Th2 for protein antigens upon epicutaneous immunization.

Both dendritic cells and basophils have been shown to influence T helper 2 cell induction, however the relative importance of their roles remains unclear. Otsuka et al. find that basophils present hapten and peptide antigens to T cells, but are unable to present protein antigens in the absence of dendritic cells.

CD8⁺ tumor-infiltrating lymphocytes at primary sites as a possible prognostic factor of cutaneous angiosarcoma

Tumor-infiltrating lymphocytes (TILs) have been reported as a prognostic factor in various cancers and are a promising target for immunotherapy. To investigate whether TILs have any impact on the prognosis of angiosarcoma patients, 55 non-treated patients (40 patients at stage 1 with cutaneous localized tumors, 4 patients at stage 2 with lymph node metastases and 11 patients at stage 3 with distant metastases) with angiosarcoma were evaluated retrospectively by immunohistochemistry stained CD4, CD8, FOXP3 and Ki67. The Kaplan-Meier method was used to estimate overall survival with patients at stage 1. Survival differences were analyzed by the log-rank test. Patients with higher numbers of CD8(+) TILs in their primary tumors survived significantly longer compared with patients with lower values. Moreover, the number of CD8 in TILs was positively correlated with a distant metastasis-free period. The total number of primary TILs (CD4 plus CD8) and CD8(+) primary TILs of stage 3 patients with distant metastases was positively correlated with their overall survival. To evaluate whether CD8(+) effector T cells are activated or differentiated, flow cytometric analysis of peripheral blood mononuclear cells (PBMC) was performed. The percentages of CD8(+) T cells producing IFN-γ in PBMC were significantly higher in patients with angiosarcoma (n = 10) compared not only with that of healthy controls (n = 20) but also patients with advanced melanoma (n = 11). These results suggest that anti-tumor immunity is clinically relevant in angiosarcoma.

Analysis of the mechanism underlying contact hypersensitivity-induced hair growth (161.13)

Alopecia areata (AA) is believed to be a tissue-specific autoimmune disease mediated by T cells. Topical immunotherapy using contact sensitizer such as squaric acid dibutylester (SADBE) is one of the most effective treatments for intractable AA. However, the precise mechanism under which topical immunotherapy, i.e., contact hypersensitivity (CHS) reaction, induces hair regrowth in AA remains to be elucidated. It has been reported that CHS in the skin lesion of human and murine AA modulates the composition of the peribulbar mononuclear cell infiltrate, which may abrogate autoimmune reaction and promote hair regrowth. In fact, we have revealed that CHS induces predominant accumulation of CD4+Foxp3+ regulatory T cells and elevated expression of Il10 in the skin, which might contribute to tolerance induction in the AA lesion after topical immunotherapy. In addition, interestingly, CHS induces hair growth not only in bald skin of AA mouse but also in telogen skin of non-alopetic mice, implying the possibility that some mechanism other than abrogating autoimmunity may underlie the effect of topical immunotherapy in AA. In this study, we have disclosed the underlying mechanism of CHS-induced hair growth in alopetic and non-alopetic skin, which may provide a fundamental finding for the development of a better topical immunotherapy for AA.

Perturbations of both nonregulatory and regulatory FOXP3+ T cells in patients with malignant melanoma

BACKGROUND

'FOXP3+ regulatory T cells' (Tregs) are reported to be increased in tumour-bearing hosts including patients with melanoma, leading to tumour immune suppression. However, this idea is challenged by recent evidence that the 'FOXP3+ Treg' fraction in fact contains activated 'nonregulatory' T cells. Also, FOXP3+ T cells are reported to have functionally and kinetically distinct subsets.

OBJECTIVES

To investigate whether either or both of regulatory and 'nonregulatory' FOXP3+ T cells are perturbed in patients with melanoma.

METHODS

FOXP3+ T cells were classified into three subsets, namely CD45RO+FOXP3(low) nonregulatory T cells, CD45RO+FOXP3(high) effector Tregs, and CD45RO-FOXP3(low) naïve Tregs, according to their expression levels of FOXP3 and CD45RO. The percentage and cytokine production of these FOXP3+ T-cell subsets were assessed by flow cytometry.

RESULTS

Both regulatory and nonregulatory T cells were increased in patients with melanoma. Moreover, we found three unexpected perturbations in FOXP3+ T-cell subsets: (i) patients with melanoma showed higher frequencies of FOXP3(low) nonregulatory T cells, which decreased and normalized after tumour removal; (ii) FOXP3(low) naïve Tregs containing higher frequencies of interferon-γ+ cells increased with tumour progression; and (iii) CD45RO+FOXP3(high) effector Tregs were pronouncedly infiltrated around tumour tissues.

CONCLUSIONS

These findings demonstrate that patients with melanoma have distinct and differential perturbation of both regulatory and nonregulatory FOXP3+ T cells. The degree of perturbation is associated with tumour burden and progression, suggesting that the perturbation reflects fundamental pathophysiological processes in patients with melanoma. The presented analysis provides a practical approach to investigate the immunological environment of cancer patients.