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Dendritic epidermal T cells (DETCs) have been shown to promote wound healing. However, the mechanisms involved need to be better understood. In the present study, we investigated the role and mechanism of DETCs in deep tissue pressure injury (DTPI). We established the DTPI model using C57BL/6 mice. Then, DTPI was evaluated and analyzed by histological staining, immunohistochemistry, real-time PCR, Western blotting, and flow cytometry in different treatment groups (DETCs, DETCs/gel, Matrigel, Saline, and Normal group). The results showed that insulin-like growth factor 1 and vascular endothelial growth factor-A expression increased after local DETCs and DETCs/gel implantation in DTPI on days 3 and 7. M1 (inducible nitric oxide synthas-marked) macrophages were predominant at 3 days after DTPI. At 7 days, M1 macrophages were decreased, and M2 (CD206-marked) macrophages were increased in the DETCs and DETCs/gel groups. In vitro, in the co-culture of DETCs and RAW264.7, CD206 expression was significantly increased in M2 macrophages. In addition, Interleukin-17A initially inhibited wound healing 1 day after injury. However, it promoted wound healing at 7, 14, and 21 days after treatment with DETCs and DETCs/gel, respectively. In conclusion, our data suggest that exogenous DETCs improve DTPI wound healing by regulating M1 to M2 macrophage polarization. [Display omitted] • Exogenous DETCs improved wound healing primarily through regulating M2 macrophage polarity in the DTPI. • Exogenous DETCs may regulate the IL-17 A mediated macrophage immune response in DTPI. [ABSTRACT FROM AUTHOR]

Objective To investigate the impact of exosomes derived from adipose tissue mesenchymal stem cells (ADSCs-exo) on dendritic epidermal T cells (DETC) and inflammation in cutaneous wounds of mice. Method From January to December 2023, ADSCs were isolated using the type I collagenase digestion method, while ADSCs-exo were obtained through differential ultracentrifugation. DETCs were extracted and cultured in primary culture, with cell purity confirmed by flow cytometry. An inflammation model of DETC cells was established in vitro using cleaved soybean protein A (ConA), and the mRNA expressions of IL-2 and IL-17A in cells were analyzed by RT-qPCR. A full-thickness skin defect wound model was created on the back skin of C57 mice, which were then divided into a blank control group, a PBS injection group, and an ADSCs-exo injection group. The levels of IL-17A, Akt, and P-Akt at the wound edge were assessed by Western blotting. The expression of DETCs at the wound edge was observed via flow cytometry. Results In the DETC in vitro inflammation model, the mRNA expressions of IL-2 and IL-17A were significantly elevated in the ConA group compared to the Control group. However, in the ConA+ADSCs-exo groups, there was a noticeable decrease in mRNA expressions of IL-2 and IL-17A when compared to the ConA group. During the mouse wound healing process, lower levels of IL-17A content were detected at the skin edge of wounds treated with ADSCs-exo compared to those treated with PBS or left untreated (control). Additionally, higher expression levels of P-Akt were observed at these sites as well. On day one after acute trauma, both PBS and ADSCs-exo treatments resulted in significantly increased migration and enrichment degree of DETC cells at wound edges compared to control samples. By day three post-injury, while DETC expression remained significantly higher for PBS-treated wounds relative to controls; its expression decreased within ADSCs-ex-o-treated wounds and reached similar levels as seen in control samples. Conclusion ConA can stimulate activated DETC to secrete IL-17A and IL-2, whereas ADSCs-exo significantly suppress the expression of IL-2 and IL-17A. During the process of wound healing in mice, ADSCs-exo inhibit the expression of IL-17A while promoting P-Akt expression. The expression of DETC at the wound site can be upregulated in response to acute trauma; although ADSCs-exo do not exhibit obvious chemotactic enrichment effect on DETC, the inhibition of DETC expression effectively impedes the occurrence of persistent and excessive inflammatory reactions in the wound, thereby ensuring a more controlled and regulated healing process. [ABSTRACT FROM AUTHOR]

Abstract Background Efficient re-epithelialization is important for successful skin wound healing. The proportion of epidermal stem cells (EpSCs) and dendritic epidermal T cells (DETCs) determines the extent of wound re-epithelialization, especially in large areas of skin tissue loss. However, it remains unknown whether and how DETCs regulate the status of EpSCs to impact wound re-epithelialization. Methods To investigate how DETCs regulate EpSCs in skin re-epithelialization, we utilized normal or full-thickness skin deficient wide type (WT) mice and Tcrσ knockout (Tcrσ−/−) mice with DETCs or DETCs-derived exosomes (Exos) treatment. Flow cytometry analysis (FCAS), BrdU labelled experiments, immunofluorescence and immunohistochemical assays were performed to detect the proportion of EpSCs in the epidermis. Wound closure rate and re-epithelialization were assayed by a macroscopical view and hematoxylin–eosin (H&E) staining. EpSCs in vitro were co-cultured with DETCs in a transwell-dependent or -independent manner, or supplement with GW4869 or Exos (5 µg/mL, 15 µg/mL and 45 µg/mL), and the proliferation of EpSCs was detected by means of FCAS and CFSE. Results Our data showed that the proportion of CD49fbriCD71dim cells, K15+ cells and BrdU+ cells in the normal epidermis of Tcrδ−/− mice had no significant difference compared to WT mice. For wounded Tcrδ−/− mice, DETCs treatment increase the proportion of CD49fbriCD71dim cells, K15+ cells and BrdU+ cells in the epidermis around the wound in comparison to PBS treatment. DETCs significantly increased the number of CD49fbriCD7dim cells and K15+ cells through transwell-dependent or -independent manners relative to control group. Furthermore, Exos stimuli remarkedly promote the proliferation of EpSCs compared to control group, while the increasement was suppressed when DETCs were interfered with GW4869. Gross observation and H&E staining showed that Exos significantly accelerated wound closure and increased re-epithelialization length in Tcrδ−/− mice when compared to control mice. Additionally, we found in vivo that Exos observably facilitated the proliferation of CD49fbriCD7dim cells and K15+ cells. Conclusions We revealed that DETCs enhanced the proliferation of EpSCs in the epidermis around the wounds to accelerate re-epithelialization in which Exos played important roles in the remote regulation of EpSCs proliferation. Together, these findings suggest a mechanistic link among DETC-derived exosomes, the proliferation of EpSCs, and wound re-epithelialization in the skin.

Background: Efficient re-epithelialization is important for successful skin wound healing. The proportion of epidermal stem cells (EpSCs) and dendritic epidermal T cells (DETCs) determines the extent of wound re-epithelialization, especially in large areas of skin tissue loss. However, it remains unknown whether and how DETCs regulate the status of EpSCs to impact wound re-epithelialization. Methods: To investigate how DETCs regulate EpSCs in skin re-epithelialization, we utilized normal or full-thickness skin deficient wide type (WT) mice and Tcrσ knockout (Tcrσ−/−) mice with DETCs or DETCs-derived exosomes (Exos) treatment. Flow cytometry analysis (FCAS), BrdU labelled experiments, immunofluorescence and immunohistochemical assays were performed to detect the proportion of EpSCs in the epidermis. Wound closure rate and re-epithelialization were assayed by a macroscopical view and hematoxylin–eosin (H&E) staining. EpSCs in vitro were co-cultured with DETCs in a transwell-dependent or -independent manner, or supplement with GW4869 or Exos (5 µg/mL, 15 µg/mL and 45 µg/mL), and the proliferation of EpSCs was detected by means of FCAS and CFSE. Results: Our data showed that the proportion of CD49fbriCD71dim cells, K15+ cells and BrdU+ cells in the normal epidermis of Tcrδ−/− mice had no significant difference compared to WT mice. For wounded Tcrδ−/− mice, DETCs treatment increase the proportion of CD49fbriCD71dim cells, K15+ cells and BrdU+ cells in the epidermis around the wound in comparison to PBS treatment. DETCs significantly increased the number of CD49fbriCD7dim cells and K15+ cells through transwell-dependent or -independent manners relative to control group. Furthermore, Exos stimuli remarkedly promote the proliferation of EpSCs compared to control group, while the increasement was suppressed when DETCs were interfered with GW4869. Gross observation and H&E staining showed that Exos significantly accelerated wound closure and increased re-epithelialization length in Tcrδ−/− mice when compared to control mice. Additionally, we found in vivo that Exos observably facilitated the proliferation of CD49fbriCD7dim cells and K15+ cells. Conclusions: We revealed that DETCs enhanced the proliferation of EpSCs in the epidermis around the wounds to accelerate re-epithelialization in which Exos played important roles in the remote regulation of EpSCs proliferation. Together, these findings suggest a mechanistic link among DETC-derived exosomes, the proliferation of EpSCs, and wound re-epithelialization in the skin. [ABSTRACT FROM AUTHOR]

Dendritic epidermal T cells (DETCs) are γδ T cells expressing invariant Vγ5Vδ1 T cell receptor (TCR) in murine epidermis. Initially, the development and the maturation of DETC progenitors are mediated by skint-1, TCR, and cytokines in the fetal thymus. Then, the DETC progenitors migrate to the epidermis with the guidance of selectins, CCR10, CCR4, etc. Eventually, mature DETCs proliferate and maintain a homeostatic population in the epidermis through IL-15 and aryl hydro-carbon receptor signaling. In “stressed” skin, DETCs are activated, exhibiting features such as a round morphology, cytotoxicity, and production of cytokines. In cutaneous carcinoma, DETCs generally inhibit tumor development directly in non-major histocompatibility complex-restricted manner, with the assistance of cytokines. DETCs also recognize and inhibit tumor via TCR, non-TCR receptors (such as 2B4 and NKG2D), or both. This study summarizes the biogenesis and the function of DETCs in cutaneous carcinoma and clarifies the essential surveillance role in the epidermis that DETCs play. As there are no DETCs in human epidermis but only human epidermis γδ T cells, we need to understand the anti-tumor pathways used by DETCs to find analogous immune pathways in human skin, which could be exploited for novel therapeutics.

Allergic contact dermatitis (ACD) is a common inflammatory skin disease with a prevalence of approximately 20% in the European population. ACD is caused by contact allergens that are reactive chemicals able to modify non-immunogenic self-proteins to become immunogenic proteins. The most frequent contact allergens are metals, fragrances, and preservatives. ACD clinically manifests as pruritic eczematous lesions, erythema, local papules, and oedema. ACD is a T cell-mediated disease, involving both CD4+ and CD8+ T cells. In addition, γδ T cells appear to play an important role in the immune response to contact allergens. However, it is debated whether γδ T cells act in a pro- or anti-inflammatory manner. A special subset of γδ T cells, named dendritic epidermal T cells (DETC), is found in the epidermis of mice and it plays an important role in immunosurveillance of the skin. DETC are essential in sensing the contact allergen-induced stressed environment. Thus, allergen-induced activation of DETC is partly mediated by numerous allergen-induced stress proteins expressed on the keratinocytes (KC). Several stress proteins, like mouse UL-16-binding protein-like transcript 1 (Mult-1), histocompatibility 60 (H60) and retinoic acid early inducible-1 (Rae-1) α-ε family in mice and major histocompatibility complex (MHC) class I—chain-related A (MICA) in humans, are upregulated on allergen-exposed KC. Allergen-induced stress proteins expressed on the KC are consequently recognized by NKG2D receptor on DETC. This review focuses on the role of γδ T cells in ACD, with DETC in the spotlight, and on the role of stress proteins in contact allergen-induced activation of DETC.

Dendritic epidermal T cells (DETCs) are γδ T cells expressing invariant Vγ5Vδ1 T cell receptor (TCR) in murine epidermis. Initially, the development and the maturation of DETC progenitors are mediated by skint-1, TCR, and cytokines in the fetal thymus. Then, the DETC progenitors migrate to the epidermis with the guidance of selectins, CCR10, CCR4, etc. Eventually, mature DETCs proliferate and maintain a homeostatic population in the epidermis through IL-15 and aryl hydro-carbon receptor signaling. In "stressed" skin, DETCs are activated, exhibiting features such as a round morphology, cytotoxicity, and production of cytokines. In cutaneous carcinoma, DETCs generally inhibit tumor development directly in non-major histocompatibility complex-restricted manner, with the assistance of cytokines. DETCs also recognize and inhibit tumor via TCR, non-TCR receptors (such as 2B4 and NKG2D), or both. This study summarizes the biogenesis and the function of DETCs in cutaneous carcinoma and clarifies the essential surveillance role in the epidermis that DETCs play. As there are no DETCs in human epidermis but only human epidermis γδ T cells, we need to understand the anti-tumor pathways used by DETCs to find analogous immune pathways in human skin, which could be exploited for novel therapeutics. [ABSTRACT FROM AUTHOR]

Allergic contact dermatitis (ACD) is a common inflammatory skin disease with a prevalence of approximately 20% in the European population. ACD is caused by contact allergens that are reactive chemicals able to modify non-immunogenic self-proteins to become immunogenic proteins. The most frequent contact allergens are metals, fragrances, and preservatives. ACD clinically manifests as pruritic eczematous lesions, erythema, local papules, and oedema. ACD is a T cell-mediated disease, involving both CD4+ and CD8+ T cells. In addition, γδ T cells appear to play an important role in the immune response to contact allergens. However, it is debated whether γδ T cells act in a pro- or anti-inflammatory manner. A special subset of γδ T cells, named dendritic epidermal T cells (DETC), is found in the epidermis of mice and it plays an important role in immunosurveillance of the skin. DETC are essential in sensing the contact allergen-induced stressed environment. Thus, allergen-induced activation of DETC is partly mediated by numerous allergen-induced stress proteins expressed on the keratinocytes (KC). Several stress proteins, like mouse UL-16-binding protein-like transcript 1 (Mult-1), histocompatibility 60 (H60) and retinoic acid early inducible-1 (Rae-1) α-ε family in mice and major histocompatibility complex (MHC) class I—chain-related A (MICA) in humans, are upregulated on allergen-exposed KC. Allergen-induced stress proteins expressed on the KC are consequently recognized by NKG2D receptor on DETC. This review focuses on the role of γδ T cells in ACD, with DETC in the spotlight, and on the role of stress proteins in contact allergen-induced activation of DETC. [ABSTRACT FROM AUTHOR]

The metabolic requirements change during cell proliferation and differentiation. Upon antigen-stimulation, effector T cells switch from adenosine-triphospate (ATP)-production by oxidative phosphorylation in the mitochondria to glycolysis. In the gut it was shown that short chain fatty acids (SCFA), fermentation products of the microbiota in colon, ameliorate inflammatory reactions by supporting the differentiation of regulatory T cells. SCFA are a major energy source, but they are also anabolic metabolites, histone-deacetylase-inhibitors and activators of G protein receptors. Recently, it was reported that a topical application of the SCFA butyrate promotes regulatory T cells in the skin. Here we ask if the SCFA butyrate, propionate and acetate affect the energy metabolism and inflammatory potential of dendritic epidermal T cells (DETC), the innate resident skin γδ T cell population. Using the Seahorse™ technology, we measured glycolysis and oxidative phosphorylation (OXPHOS) in a murine DETC cell line, 7-17, upon TCR-stimulation by CD3/CD28 crosslinking, with or without SCFA addition. TCR engagement resulted in a change of the ratio glycolysis/OXPHOS. A similar metabolic shift has been described for activated CD4 T cells. Addition of 5 mM SCFA, in particular butyrate, antagonized the effect. Stimulated DETC secrete cytokines, e.g. the pro-inflammatory cytokine interferon-gamma (IFNγ), and thereby regulate skin homeostasis. Addition of butyrate and propionate to the cultures at non-toxic concentrations decreased secretion of IFNγ by DETC and increased the expression of the immunoregulatory surface receptor CD69. We hypothesize that SCFA can dampen the inflammatory activity of DETC. [ABSTRACT FROM AUTHOR]

Dendritic epidermal T cells (DETCs) and dermal Vγ4 T cells engage in wound re-epithelialization and skin inflammation. However, it remains unknown whether a functional link between Vγ4 T cell pro-inflammation and DETC pro-healing exists to affect the outcome of skin wound closure. Here, we revealed that Vγ4 T cell-derived IL-17A inhibited IGF-1 production by DETCs to delay skin wound healing. Epidermal IL-1β and IL-23 were required for Vγ4 T cells to suppress IGF-1 production by DETCs after skin injury. Moreover, we clarified that IL-1β rather than IL-23 played a more important role in inhibiting IGF-1 production by DETCs in an NF-κB-dependent manner. Together, these findings suggested a mechanistic link between Vγ4 T cell-derived IL-17A, epidermal IL-1β/IL-23, DETC-derived IGF-1, and wound-healing responses in the skin.

Dendritic epidermal T cells (DETCs) and dermal Vγ4 T cells engage in wound re-epithelialization and skin inflammation. However, it remains unknown whether a functional link between Vγ4 T cell pro-inflammation and DETC pro-healing exists to affect the outcome of skin wound closure. Here, we revealed that Vγ4 T cell-derived IL-17A inhibited IGF-1 production by DETCs to delay skin wound healing. Epidermal IL-1β and IL-23 were required for Vγ4 T cells to suppress IGF-1 production by DETCs after skin injury. Moreover, we clarified that IL-1β rather than IL-23 played a more important role in inhibiting IGF-1 production by DETCs in an NF-κB-dependent manner. Together, these findings suggested a mechanistic link between Vγ4 T cell-derived IL-17A, epidermal IL-1β/IL-23, DETC-derived IGF-1, and wound-healing responses in the skin. [ABSTRACT FROM AUTHOR]

A study describing the H, C and N backbone and side chain chemical shift assignments and secondary structure of Skint-1 a prototypic member of a family of mouse genes, of which Skint-1 is involved in the development of the dendritic epidermal T cell (DETC) subset of γδ T cells. [ABSTRACT FROM AUTHOR]

Chronic skin inflammation resulting from a defective epidermal barrier is a hallmark of atopic dermatitis (AD). We previously demonstrated that mice lacking FGF receptors 1 and 2 in keratinocytes (K5-R1/R2 mice) develop an AD-like chronic dermatitis as a result of an impaired epidermal barrier. Here, we show that γδ T cells, which rapidly respond to various insults, accumulate in the epidermis of K5-R1/R2 mice before the development of histological abnormalities. Their number and activation further increase as the phenotype progresses, most likely as a consequence of increased expression of Il-2 and Il-7 and the stress-induced proteins Rae-1, H60c, Mult1, PlexinB2, and Skint1. To determine the role of γδ T cells in the skin phenotype, we generated quadruple mutant K5-R1/-R2 mice lacking γδ T cells. Surprisingly, loss of γδ T cells did not or only marginally affect keratinocyte proliferation, epidermal thickness, epidermal barrier function, and accumulation and activation of different immune cells in the skin of K5-R1/R2 mice, possibly due to partial compensation by αβ T cells. These results demonstrate that γδ T cells do not contribute to the development or maintenance of chronic inflammation in response to a defect in the epidermal barrier. [ABSTRACT FROM AUTHOR]

Background Chronic alcoholism is associated with increased incidence and severity of cutaneous infection. Skin-resident T cells orchestrate numerous immunological functions that are critically involved in both tissue homeostasis and cutaneous immunity. The impact of chronic ethanol (Et OH) exposure on skin T cells has not previously been examined; given their important role in maintaining the immune barrier function of the skin further study is warranted. Methods Mice were administered Et OH in the drinking water for 12 to 16 weeks. Flow cytometry was used to evaluate impact of Et OH feeding on skin T cell numbers, rates of proliferation, and apoptosis as well as activation marker expression and cytokine production after ex vivo stimulation. Results Chronic Et OH feeding caused a baseline reduction in dendritic epidermal T cell ( DETC) numbers that corresponded with reduced expression of the activation marker JAML following phorbol 12-myristate 13-acetate ( PMA)/ionomycin stimulation. Chronic Et OH feeding did not alter total numbers of dermal T cells, but specific subset loss was observed in Foxp3+ regulatory T cells (Tregs) as well as CD3hi, Vγ3+ and CD3int, Vγ3− dermal γδ T cells. Et OH-induced dysfunction in the latter population, which represents prototypical interleukin-17 (IL-17)-producing dermal γδT17s, was made evident by diminished IL-17 production following anti- CD3 stimulation. Additionally, the capacity of lymph node γδ T cells to produce IL-17 following anti- CD3 and PMA/ionomycin stimulation was impaired by chronic Et OH feeding. Conclusions Chronic Et OH feeding induced defects in both numbers and function of multiple skin T cell subsets. The decreased density and poor responsiveness of DETCs and γδT17 cells in particular would be expected to compromise immune effector mechanisms necessary to maintain a protective barrier and restrict pathogen invasion. These findings demonstrate the sensitivity of skin T cells to Et OH and provide new mechanisms to help explain the propensity of alcoholics to suffer skin infection. [ABSTRACT FROM AUTHOR]

Dendritic epidermal T cells (DETC) express an invariant Vγ3/Vδ1 T-cell receptor, appear in fetal epidermis, and form a population of resident epidermal T cells. Their temporal development in the thymus has been studied extensively. However, little is known about the mechanisms involved in the embryonic trafficking of DETC from thymus to epidermis. We demonstrate that DETC in adult skin, as well as the DETC precursors in fetal thymus, express E and P selectin ligands (E- and P-hg). Mice deficient in α1,3 fucosyltransferases IV and VII (FTIV/VII) cannot synthesize the carbohydrate motifs that form key elements of these selectin ligands. The numbers of DETC in the epidermis of FTIV/VII-/- mice were dramatically reduced compared with normal mice. However, the development of DETC precursors in fetal thymus was identical in normal and FTIV/VII-/- mice, suggesting that the DETC precursors produced in FTIV/VII-/- mice could not traffic effectively to skin because they lack E- and P-hg. We tested this hypothesis by daily injection of blocking antibodies against E and P selectin into pregnant mice. Mice born from dams treated with anti-selectin antibodies, but not those born from dams treated with isotype control, had significantly diminished numbers of DETC. To test the role of chemokine receptors in DETC skin homing, we examined skin from CCR4-/- and CCR10-/- mice, respectively. DETC were significantly reduced in CCR4-/- mice but were present at normal levels in CCR10-/- mice. Our results present evidence forthe crucial role of trafficking molecules in embryonic migration of DETC precursors to skin. [ABSTRACT FROM AUTHOR]

Solar radiation in the UVB range is absorbed primarily by the epidermal DNA where characteristic photodamage results in altered immune responses and mutagenic lesions. UVB exposure of the skin results in a profound upregulation of the anti-inflammatory cytokine, IL-10 and suppression of contact hypersensitivity (CHS). Given that IL-10 is produced after UVB exposure, and that antibodies against IL-10 have been shown to reverse UVB-induced immune suppression, we hypothesized that IL-10 transgenic mice would show an enhanced immune suppression in response to UVB. Using an IL-10 transgenic mouse model (IL-10tg), we examined the CHS response in unexposed animals and those exposed to UVB. Unexposed IL-10tg animals showed a diminished CHS response compared to wild-type. Surprisingly, however, when IL-10tg animals were exposed to UVB, the CHS response was not further suppressed, but rather was restored to the level observed in unexposed wild-type animals. [ABSTRACT FROM AUTHOR]

CD200 is a widely expressed transmembrane glycoprotein that transmits an inhibitory signal after ligation of the structurally homologous CD200-receptor-1 (CD200R1). Recently, we showed that CD200 is expressed on keratinocytes and plays a role in protecting hair follicles from autoimmune attack. Here, we report the characterization of cell surface and mRNA expression of CD200R1 by cells of the murine epidermis. In addition, we report mRNA expression for other members of the CD200R-family (R2–R4) by quantitative real-time RT-PCR. Variable levels of CD200R1, R2, R3, and R4 mRNA were detected in bulk epidermal cell suspensions. Freshly isolated Langerhans cells (LC) preferentially expressed CD200R1. Consistent with an inhibitory role for CD200:CD200R1 interaction, LC obtained from mice deficient in CD200 (CD200−/−) were in a heightened state of activation as compared with wild-type (CD200+/+) cells. Freshly isolated dendritic epidermal T cells (DETC) expressed low levels of CD200R1, R2, and R3 mRNA, but they preferentially increased cell surface and mRNA expression of CD200R1 upon activation in vitro. In functional assays using sub-optimal CD3 signaling, immobilized CD200 inhibited DETC proliferation and cytokine secretion. Collectively, these results suggest that CD200:CD200R interactions may play a role in regulating both LC and DETC in cutaneous immune reactions. [ABSTRACT FROM AUTHOR]

Endo Y, Ishikawa O, Negishi I. Zeta-chain-associated protein-70 molecule is essential for the proliferation and the final maturation of dendritic epidermal T cells.Adult murine epidermis contains members of the epithelialγδ T-cell family called dendritic epidermal T cells (DETCs). Their development and maturation have been the subjects of investigations, but the details are still unclear. T-cell receptor (TCR) zeta-chain-associated protein-70 (ZAP-70), one of the protein tyrosine kinases required for TCR signaling, plays a pivotal role in the development ofαβ T cells. In mice lacking ZAP-70, thymic development ofαβ T cells was completely arrested at the immature CD4+CD8+ TCRlow stage. Here, we examined whether or not the development and maturation of DETCs were altered in ZAP-70-deficient mice. Immunohistochemical analyses of epidermal sheets revealed that the number of DETCs was reduced and their characteristic dendrites were lost or markedly shortened in ZAP-70–/– mice. In flow cytometric analyses, the expression levels ofγδ TCR and Thy-1.2 on the ZAP-70–/– DETCs were lower than those on ZAP-70+/– DETCs. The expression of a very early activation antigen, CD69, was not detected on ZAP-70–/– DETCs, whereas CD69 was expressed on ZAP-70+/– DETCs. Furthermore, ZAP-70–/– DETCs showed markedly reduced proliferation and no IL-2 gene expression in response to anti-CD3ε or concanavalin A stimulation. These results suggest that ZAP-70 is essential for TCR signaling which induces the proliferation and the final maturation of DETCs in the epidermis. [ABSTRACT FROM AUTHOR]

1α,25-dihydroxyvitamin D3[1,25(OH)2D3], the active metabolite of vitamin D, exerts its activities by binding to the vitamin D receptor (VDR) with subsequent function as a transcription factor. Targeted ablation of the VDR in mice results in rickets and alopecia.To study the consequences of VDR deficiency for skin physiology, and to investigate the mechanisms of the immunosuppressive effect of 1,25(OH)2D3 on LC.We studied the structural, phenotypic and functional properties of skin and individual skin leucocyte populations in VDR–/– mice.The lack of VDR induced a wide spectrum of pathologies including dermal deposition of collagen, enlargement of sebaceous glands, dilation of the hair follicles, development of epidermal cysts, increased numbers of dendritic epidermal T cells (DETC) and hyperkeratosis. Ageing aggravated these changes. Intriguingly, Langerhans cells (LC) were indistinguishable in distribution, morphology and number compared with controls.In vitro, LC underwent a maturation/migration process similar to LC from control mice. Pretreatment of epidermal cells or LC-enriched epidermal cell suspensions with 1,25(OH)2D3 impaired LC maturation and T-cell stimulatory capacity from VDR+/+ but not VDR–/– mice, demonstrating that LC are targets of vitamin D3 and that interaction between vitamin D3 and LC results in a suppression of LC activity.Our data imply that VDR expression controls dermal collagen production, hair development and growth, proliferation of sebaceous glands and the homeostasis of DETC. Surprisingly, VDR deficiency does not influence LC phenotype and function. [ABSTRACT FROM AUTHOR]

γδ T cells arc a distinct subgroup of T lymphocytes that arc enriched at certain anatomical localizations, such as the small intestinal epithelia and other epithelia. γδ T cells recognize microbial antigens, such as heat shock proteins (in mice) or phosphorylated bacterial metabolites (in humans), and control the integrity of epithelia. At the effector cell level, they share with the conventional αβ T lymphocytes potent cytotoxic activity and the capacity to produce a variety of cytokines, including specific cytokines such as keratinocyte growth factor. Here we summarize the current knowledge on the role of chemokines and their receptors in the migration and function of γδ T cells. As an example, the migration of γδ T cells to the small intestine is guided by the chemokine receptor CCR9 and the local expression of the corresponding ligand CCL25 (also termed thymus-expressed chemokine, TECK), Chemokine receptor expression also correlates with the functional program of T cells. In this respect, the strong expression of the MIP-1α/MIP-1β/RANTES (CCL3/CCL4/CCLS)-receptor CCR5 correlates with a T-helper 1 phenotype of human Vγ9Vδ2-expressing γδ T cells. The regulation of chemokine receptors, together with the pattern of local chemokine production, plays an important role in the localization of γδ T cells under physiological and pathophysiological conditions, such as infection, inflammation, and rumor defense. [ABSTRACT FROM AUTHOR]

Langerhans cells (LCs) and dendritic epidermal T cells (DETCs) constitute the skin immune system. To demonstrate the kinetics of in vivo activation of murine LCs and DETCs in the elicitation phase of contact hypersensitivity, we measured the cell area positively stained for I-A and γδT-cell receptor (or Thy-1.2), respectively, under a fluorescence microscope at various time intervals after topical application of dinitrofluorobenzene. The fluorescence-positive area of LCs increased in parallel with that of DETCs at 1 h and 24 h, indicating the biphasic activation of LCs and DETCs. Early activation was hapten-specific and often exhibited close LC-to-DETC apposition. Experiments with in vivo administration of neutralizing anticytokine antibodies revealed that none of interferon (IFN)-γ, tumour necrosis factor (TNF)-α and interleukin (IL)-1β were involved in the induction of early activation of LCs and DETCs, while TNF-α and IL-1β mediated late activation of LCs, and IFN-γ and IL-1β mediated that of DETCs. Our results indicate that LCs and DETCs are synchronously and biphasically activated in the epidermis during the elicitation phase of contact hypersensitivity and suggest that different mechanisms may control early and late activation. [ABSTRACT FROM AUTHOR]

The epidermis of mice contains, in addition to Langerhans cells, a second dendritic population that is Thy-1+/CD3+ CD4-/CD8-/T-cell receptor-Vγ3/Vδ1+. These dendritic epidermal T cells (DETC) are now thought to comprise one element in the family of epithelial tissue-resident γδT cells. In the present study, DETCs were examined for their expression of mRNA for cytokines, using a reverse transcription-polymerase chain reaction. Freshly isolated Thy-1+ epidermal cells constitutively expressed mRNA for γ-interferon, but not IL-2. Within 24 h after stimulation with Con A, these cells then expressed mRNA for γ-interferon and IL-2, but not IL-4. The rapid onset of expression of mRNA for IL-2 occurred exclusively within the Thy-1+ population, and in a Con A-dependent fashion. When freshly isolated epidermal cells were first stimulated with Con A and then expanded in bulk with rIL-2 for 20-24 d, cells expressing IL-4 mRNA then emerged, upon secondary stimulation with Con A. These "short-term" DETC lines also expressed mRNA for IL-2, interferon-γ, IL-1α, IL-3, IL-6, IL-7, tumor necrosis factor α and β, and granulocyte macrophage-colony stimulating factor. Interestingly, mRNA for IL-4 and IL-6 was no longer detected in long-term (>1 year) DETC lines 7-17 and 12-12. In addition, one line (7-17) maintained IL-3 mRNA expression, whereas another (12-12) had lost this capacity. These results emphasize the concept that, as resident cells in epidermis, DETCs exhibit several different immunorelevant activities, and the heterogeneity in cytokine mRNA profiles suggests that DETCs may divide into functional subsets. [ABSTRACT FROM AUTHOR]

Molecular studies of the δ TCR, which is expressed by a minor subpopulatlon of T lymphocytes in all vertebrate species, have defined a subset which expresses a receptor with extreme junctional diversity and a second subset, most commonly found in eplthella, which expresses a receptor of very limited diversity. In the developing murine thymus, δ T cells appear in an ordered sequence of specific v rearrangements, V3V, 1 on day 14, V2V1 on day 17, and subsequently V4V5, V6, or V7. We demonstrate that the transfer of expanded populations of δ cells from newborn thymus and cell lines expressing the invariant V3V1 receptor into SCID mice, which lack T and B cells, results in the appearance of CD3CD4CD8 thymocytes. Thus, one role of the early appearing V3V1 T cells in thymlc development is to promote CD4 and CO8 surface expression on precursor cells. [ABSTRACT FROM PUBLISHER]

Langerhans cells (LC) play a critical role in cutaneous immunity, and whereas Thy-1+ dendritic epidermal cells (Thy-1+ dEC) are also present in murine epidermis, their role remains unknown. Antigens and cytokines influence the number of LC found in the epidermis. However, there has been no investigation into the effects of particular cytokines during resolution of a viral infection. In order to study this we infected mice subcutaneously with vaccinia virus (VV) constructs containing the genes encoding TNF-α, IL-6 or IFN-γ and the density of LC, THY-1+ dEC and CD4+ cells was determined. In this system the cytokines were produced locally at the site of viral replication. Cell densities were examined at day 1, while the response was being initiated, and at day 5 as the infection was being resolved. Infection with VV, like exposure to other antigens, decreased the density of epidermal LC at day 1, and they remained depressed at day 5. Production of TNF-α during VV growth did not influence this response by LC, whereas IFN-γ and IL-6 both increased the number of epidermal Ia+ LC at day 1 but then caused a reduction at day 5. Thy-1+ dEC were not affected by VV infection at any time-point examined, nor did any cytokine influence the density of these cells at day 1. However, by day 5 IFN-γ and IL-6, but not TNF-α, decreased the number of Thy-1+ dEC. These changes in cell densities are consistent with LC but not Thy-1+ dEC playing a role in initiation of immunity against VV and a complex interplay between cytokines and these cells during the response to VV. CD4+ T cells were also attracted into the epidermis by IFN-γ and IL-6 but not by TNF-α. [ABSTRACT FROM AUTHOR]

The epidermis is the outermost layer of skin and the first barrier against invasion. Dendritic epidermal T cells (DETCs) are a subset of γδ T cells and an important component of the epidermal immune microenvironment. DETCs are involved in skin wound healing, malignancy and autoimmune diseases. DETCs secrete insulin-like growth factor-1 and keratinocyte growth factor for skin homeostasis and re-epithelization and release inflammatory factors to adjust the inflammatory microenvironment of wound healing. Therefore, an understanding of their development, activation and correlative signalling pathways is indispensable for the regulation of DETCs to accelerate wound healing. Our review focuses on the above-mentioned molecular mechanisms to provide a general research framework to regulate and control the function of DETCs., (© The Author(s) 2021. Published by Oxford University Press.)

Objective: To explore the effects of dendritic epidermal T cells (DETC) on proliferation and apoptosis of epidermal cells in wound margin of mice and its effects on wound healing. Methods: Twenty-eight healthy specific pathogen free (SPF) C57BL/6 wild-type (WT) male mice aged 8-12 weeks and 60 SPF T lymphocyte receptor δ-knockout (TCR δ(-/-)) male mice aged 8-12 weeks were selected to conduct the following experiments. (1) Eight WT mice were selected to isolate epidermal cells and primarily culture DETC according to the random number table. Morphological observation and purity identification of DETC by flow cytometer were detected immediately after culture and on culture day (CD) 15 and 30, respectively. (2) According to the random number table, 5 WT mice and 5 TCR δ(-/-) mice were selected and enrolled into WT control group and TCR δ(-/-) group. Round full-thickness skin defect with diameter of 6 mm was made on the back of each mouse. The wound healing condition was observed immediately after injury and on post injury day (PID) 2, 4, 6, 8, 10, and the percentage of residual wound area was calculated. (3) Mice were selected to group and reproduce model of full-thickness skin defect as in experiment (2). On PID 3, the tissue of wound margin was collected for hematoxylin eosin staining, and the length of new epithelium was measured. (4) Mice were selected to group and reproduce model of full-thickness skin defect as in experiment (2). On PID 3, epidermal tissue of wound margin was collected to determine expression of proliferating cell nuclear antigen (PCNA) using Western blotting for evaluation of proliferation of epidermal cell. (5) Mice were selected to group and reproduce model of full-thickness skin defect as in experiment (2). On PID 3, epidermal tissue of wound margin was selected and digested into single-cell suspension, and apoptosis of cells was detected by flow cytometer. (6) Forty TCR δ(-/-) mice were selected to carry out the same treatment as in experiments (2)-(5). According to the random number table, these mice were enrolled into TCR δ(-/-) control group and TCR δ(-/-)+ DETC group, with 5 mice in each group for each experiment. Round full-thickness skin defect was made on the back of each mouse. DETC in the number of 1×10(5) (dissolution in 100 μL phosphate with buffer purity above 90%) were injected through multiple points of wound margin of mice in TCR δ(-/-)+ DETC group immediately after injury, and equal volume of phosphate buffer was injected into mice of TCR δ(-/-) control group with the same method as above. Data were processed with one-way analysis of variance for repeated measurement, t test, and Bonferroni correction. Results: (1) Along with the culture time elapse, the number of dendritic structures of DETC increased gradually. The percentage of T lymphocytes was 4.67% and 94.1% of these T lymphocytes were DETC. The purity of DETC on CD 15 was 18.50% and the purity of DETC on CD 30 was 98.70%. (2) Immediately after injury, the wound healing condition of mice in WT control group and TCR δ(-/-) group was similar. The wound healing speed of mice in TCR δ(-/-) group was slower than that in WT control group on PID 2-10. The percentages of residual wound area of mice in TCR δ(-/-) group on PID 2, 4, 6, 8, and 10 were increased significantly compared with those in WT control group ( t =3.492, 4.425, 4.170, 4.780, 7.318, P <0.01). (3) The length of new epithelium of mice in TCR δ(-/-) group on PID 3 was (359 ± 15) μm, which was obviously shorter than that in WT control group [(462±26) μm, t =3.462, P <0.01]. (4) Immediately after injury, wound condition of mice in TCR δ(-/-)+ DETC group and TCR δ(-/-) control group was similar. Compared with TCR δ(-/-)+ DETC group, the wound healing speed of mice in TCR δ(-/-) control group were obviously slower on PID 2-10. The percentages of residual wound area of mice in TCR δ(-/-)+ DETC group on PID 2, 4, 6, 8, and 10 were decreased significantly compared with those in TCR δ(-/-) control group ( t =2.308, 3.725, 2.698, 3.707, 6.093, P <0.05 or P <0.01). (5) On PID 3, the length of new epithelium of mice in TCR δ(-/-)+ DETC group was (465±31) μm, which was obviously longer than that in TCR δ(-/-) control group [(375±21) μm, t =2.390, P <0.05]. (6) On PID 3, PCNA expression of epidermal cell in wound margin of mice in TCR δ(-/-) group was 1.25±0.04, which was obviously lower than that in WT control group (2.01±0.09, t =7.415, P <0.01). (7) On PID 3, PCNA expression of epidermal cell in wound margin of mice in TCR δ(-/-)+ DETC group was 1.62±0.08, which was significantly higher than that in TCR δ(-/-) control group (1.05±0.14, t =3.561, P <0.05). (8) On PID 3, apoptosis rate of epidermal cell in wound margin of mice in TCR δ(-/-) group was (16.1±1.4)%, which was higher than that in WT control group [(8.1±0.6)%, t =5.363, P <0.01]. (9) On PID 3, apoptosis rate of epidermal cell in wound margin of mice in TCR δ(-/-)+ DETC group was (11.4±1.0)%, which was obviously lower than that in TCR δ(-/-) control group [(15.4±1.4)%, t =2.377, P <0.05]. Conclusions: DETC participates in the process of wound healing though promoting the proliferation of epidermal cells in wound margin and inhibit the apoptosis of these cells.

The impairment of skin repair in diabetic patients can lead to increased morbidity and mortality. Proper proliferation, apoptosis and migration in keratinocytes are vital for skin repair, but in diabetic patients, hyperglycemia impairs this process. Dendritic epidermal T cells (DETCs) are an important part of the resident cutaneous immunosurveillance program. We observed a reduction in the number of DETCs in a streptozotocin-induced diabetic mouse model. This reduction in DETCs resulted in decreased IGF-1 and KGF production in the epidermis, which is closely associated with diabetic delayed wound closure. DETCs ameliorated the poor wound-healing conditions in diabetic mice by increasing keratinocyte migration and proliferation and decreasing keratinocyte apoptosis in diabetes-like microenvironments. Our results elucidate a new mechanism for diabetic delayed wound closure and point to a new strategy for the treatment of wounds in diabetic patients.

Intraepithelial γδ T cells play pivotal roles in homeostasis, tissue repair, inflammation, and protection from malignancy. In some tissues, γδ T cells are the only resident T cell population, whereas in others, they coexist with αβ T cells and other lymphocyte populations. γδ T cell function in the epithelium requires constant communication between cells in the form of cell-to-cell contacts and cell-to-matrix interactions. These interactions coordinate with the timely production of specific cytokines, chemokines, growth factors, and glycosaminoglycans, which have specialized effects on neighboring epithelial cells. Antigens that activate these T cells are not well-defined, and they do not express classic costimulatory or coreceptor molecules. As such, an understanding of the mechanisms used by epithelial γδ T cells to maintain homeostasis and facilitate wound repair has necessitated the identification of novel molecular interactions between γδ T cells and their neighboring epithelial cells.