Interleukin-7. Biology and implications for dermatology

Skin γδ T Cells and Their Function in Wound Healing

For the skin immune system, γδ T cells are important components, which help in defensing against damage and infection of skin. Compared to the conventional αβ T cells, γδ T cells have their own differentiation, development and activation characteristics. In adult mice, dendritic epidermal T cells (DETCs), Vγ4 and Vγ6 γδ T cells are the main subsets of skin, the coordination and interaction among them play a crucial role in wound repair. To get a clear overview of γδ T cells, this review synopsizes their derivation, development, colonization and activation, and focuses their function in acute and chronic wound healing, as well as the underlining mechanism. The aim of this paper is to provide cues for the study of human epidermal γδ T cells and the potential treatment for skin rehabilitation.

γδ T Cells in Skin Inflammation

Gamma delta (γδ) T cells are a subset of T lymphocytes that express T cell receptor γ and 5 chains and display structural and functional heterogeneity. γδ T cells are typically of low abundance in the body and account for 1-5% of the blood lymphocytes and peripheral lymphoid tissues. As a bridge between innate and adaptive immunity, γδ T cells are uniquely poised to rapidly respond to stimulation and can regulate immune responses in peripheral tissues. The dendritic epidermal T cells in the skin epidermis can secrete growth factors to regulate skin homeostasis and re-epithelization and release inflammatory factors to mediate wound healing during skin inflammatory responses. Dermal γδ T cells can regulate the inflammatory process by producing interleukin-17 and other cytokines or chemokines. Here, we offer a review of the immune functions of γδ T cells, intending to understand their role in regulating skin barrier integrity and skin wound healing, which may be crucial for the development of novel therapeutics in skin diseases like atopic dermatitis and psoriasis.

Effects of a complex mixture prepared from agrimonia, houttuynia, licorice, peony, and phellodendron on human skin cells

Active ingredients derived from natural sources are widely utilized in many industries. Cosmetic active ingredients are largely derived from various plants. In this study, we examined whether a mixture of plant extracts obtained from agrimonia, houttuynia, licorice, peony, and phellodendron (hereafter AHLPP), which are well-known for their effects on skin, could affect skin barrier function, inflammation, and aging in human skin cells. We also determined whether AHLPP extracts sterilized using γ-irradiation (to avoid preservatives) retained their skin cell regulating activity. The AHLPP mixture could downregulate representative pro-inflammatory cytokines including IL 1-β and IL 7. Procollagen peptide synthesis was also increased by AHLPP treatment along with mRNA upregulation of barrier proteins such as filaggrin and desmoplakin. The AHLPP mixture showed an anti-aging effect by significantly upregulating telomerase activity in human keratinocytes. We further observed TERT upregulation and CDKN1B downregulation, implying a weakening of pro-aging signal transduction. Co-cultivation of a hydrogel polymer containing the AHLPP mixture with human skin cells showed an alteration in skin-significant genes such as FLG, which encodes filaggrin. Thus, the AHLPP mixture with or without γ-irradiation can be utilized for skin protection as it alters the expression of some significant genes in human skin cells.

Expression of B and T lymphocyte attenuator, retinoid-related orphan receptor gamma-isoform-t and interleukin 7 in psoriasis vulgaris

BACKGROUND/OBJECTIVES

Psoriasis is one of the immune-mediated inflammatory diseases where CD4+ T lymphocytes, mainly Th1 cells, and B lymphocytes contribute in their pathogenesis through a pro-inflammatory effect, production of antibodies, activation of T cells and cytokine synthesis. B and T lymphocyte attenuator (BTLA) is a co-inhibitory molecule expressed on T and B lymphocytes as well as other immune cells, and it is necessary to inhibit homoeostatic expansion and activation of lymph node and skin-resident γδ T cells. BTLA expression is regulated by RORγt and IL-7. The study aimed at adding more insight on the role played by co-inhibitory molecule BTLA in psoriasis vulgaris and its inter-relation with RORγt and IL-7 to establish a basis for novel treatment strategies.

METHODS

This case-control study included 25 patients and 25 controls examined for gene expression of BTLA, RORγt and IL-7.

RESULTS

B and T lymphocyte attenuator was significantly lower in psoriasis patients, whereas both RORγt and IL-7 were higher in comparison with controls. A significant positive correlation between disease severity (PASI) and both RORγt and IL-7 as well as between RORγt and IL-7 was found. A significant negative correlation between BTLA and both RORγt and IL-7 was found. Neither the age nor the duration of disease had any correlation with BTLA, RORγt or IL-7. BTLA had no correlation with PASI. Regarding the control group, a significant negative correlation between RORγt and IL-7 was found.

CONCLUSION

B and T lymphocyte attenuator, RORγt and IL-7 play an important role in psoriasis.

Immune-centric network of cytokines and cells in disease context identified by computational mining of PubMed

Cytokines are signaling molecules secreted and sensed by immune and other cell types, enabling dynamic intercellular communication. Although a vast amount of data on these interactions exists, this information is not compiled, integrated or easily searchable. Here we report immuneXpresso, a text-mining engine that structures and standardizes knowledge of immune intercellular communication. We applied immuneXpresso to PubMed to identify relationships between 340 cell types and 140 cytokines across thousands of diseases. The method is able to distinguish between incoming and outgoing interactions, and it includes the effect of the interaction and the cellular function involved. These factors are assigned a confidence score and linked to the disease. By leveraging the breadth of this network, we predicted and experimentally verified previously unappreciated cell-cytokine interactions. We also built a global immune-centric view of diseases and used it to predict cytokine-disease associations. This standardized knowledgebase (http://www.immunexpresso.org) opens up new directions for interpretation of immune data and model-driven systems immunology.

Modulation of activation-associated host cell gene expression by the apicomplexan parasite Theileria annulata

Infection of bovine leucocytes by Theileria annulata results in establishment of transformed, infected cells. Infection of the host cell is known to promote constitutive activation of pro-inflammatory transcription factors that have the potential to be beneficial or detrimental. In this study we have compared the effect of LPS activation on uninfected bovine leucocytes (BL20 cells) and their Theileria-infected counterpart (TBL20). Gene expression profiles representing activated uninfected BL20 relative to TBL20 cells were also compared. The results show that while prolonged stimulation with LPS induces cell death and activation of NF-κB in BL20 cells, the viability of Theileria-infected cells was unaffected. Analysis of gene expression networks provided evidence that the parasite establishes tight control over pathways associated with cellular activation by modulating reception of extrinsic stimuli and by significantly altering the expression outcome of genes targeted by infection-activated transcription factors. Pathway analysis of the data set identified novel candidate genes involved in manipulation of cellular functions associated with the infected transformed cell. The data indicate that the T. annulata parasite can irreversibly reconfigure host cell gene expression networks associated with development of inflammatory disease and cancer to generate an outcome that is beneficial to survival and propagation of the infected leucocyte.

Cutaneous T-cell lymphoma occurring with a melanocytic proliferation, masquerading as a nonhealing ulcer with reactive changes

Two of the most challenging areas in dermatopathology are lymphoproliferative disorders and melanocytic lesions. We present a case of peripheral T-cell lymphoma occurring with an intradermal melanocytic proliferation. A 63-year-old Caucasian man presented with a 12-cm edematous, erythematous to violaceous, scalp ulceration that had enlarged over six months. Previous biopsies showed reactive changes which were concerning for infection. The last biopsies showed small to intermediate sized, angulated cells with clear cytoplasm within the dermis, with extension into the epidermis. These cells stained positive with markers for CD3, CD45RO and CD43, yet showed decreased expression of pan-T-cell markers CD5 and CD7, and absent expression of CD4, CD8, CD56 and CD57 and EBV. Molecular studies showed a clonal T-cell receptor gamma chain gene rearrangement. The diagnosis was peripheral T-cell lymphoma, unspecified. Another biopsy from an indurated area separate from the ulcer showed scattered, enlarged cells embedded in the same lymphocytic infiltrate. No mitotic figures were identified. These cells stained for S100 and Melan-A, in a partly nested arrangement. This was felt to represent a melanocytic nevus. This case likely represents an extraordinary coincidence of two distinctly different neoplasms.

Serum cytokines and growth factor levels in Japanese patients with psoriasis

BACKGROUND

Although the precise pathomechanism of psoriasis is still unknown, various cytokines and growth factors derived from T cells, dendritic cells or keratinocytes, are critically involved in this disease. There have been several studies determining the serum levels of cytokines in patients with psoriasis, but with conflicting results. The levels of various cytokines and growth factors were measured in the sera of patients with psoriasis and compared with those of healthy controls. The correlation with disease severity was also determined.

METHODS

Sera were collected from 122 patients with psoriasis and 78 healthy controls for ELISA analysis to evaluate the levels of cytokines and growth factors. The severity of psoriasis was determined by the Psoriasis Area and Severity Index (PASI).

RESULTS

Serum levels of tumour necrosis factor (TNF)-alpha, interferon (IFN)-gamma, interleukin (IL)-2, IL-6, IL-7, IL-8, IL-12, IL-17, IL-18 and vascular endothelial growth factor (VEGF) were significantly increased in patients with psoriasis compared with those of healthy controls. The serum levels of IL-2, soluble intercellular adhesion molecule-1, epidermal growth factor, hepatocyte growth factor and amphiregulin were not significantly different from those of healthy controls. Increased serum levels of TNF-alpha, IFN-gamma, IL-12, IL-17, IL-18 and VEGF correlated with PASI. Furthermore, these cytokine levels were decreased after psoriasis treatment. In contrast, serum levels of IL-10 were decreased in psoriasis and negatively correlated with PASI.

DISCUSSION

Serum levels of TNF-alpha, IFN-gamma, IL2, IL-6, IL-7, IL-8, IL-12, IL-17, IL-18 and VEGF were positively correlated and that of IL-10 was negatively correlated with PASI in Japanese patients with psoriasis. These parameters might be useful for determining the disease activity of psoriasis.

Cytokine secretion profiles of human keratinocytes during Trichophyton tonsurans and Arthroderma benhamiae infections

Dermatophytes cause intractable superficial infections in humans. Arthroderma benhamiae, a zoophilic dermatophyte, triggers severe inflammatory responses in humans, while Trichophyton tonsurans, an anthropophilic dermatophyte, triggers minimal ones. Cytokines and other factors derived from keratinocytes play important roles in inflammatory and immune responses in the skin. The authors performed an in vitro investigation to determine the human keratinocyte cytokine profiles during dermatophyte infection. The human keratinocyte cell line PHK16-0b was infected with A. benhamiae or T. tonsurans for 24 h, and the cytokines secreted were analysed using a human cytokine antibody array. Marked differences were observed in the cytokine profiles of the cells infected with the two dermatophytes. A. benhamiae infection resulted in the secretion of a broad spectrum of cytokines, including proinflammatory cytokines, chemokines, and immunomodulatory cytokines. In contrast, T. tonsurans-infected keratinocytes secreted only limited cytokines, including eotaxin-2, interleukin (IL)-8 and IL-16. cDNA microarray analysis confirmed that A. benhamiae infection upregulated genes encoding IL-1β, IL-2, IL-4, IL-6, IL-10, IL-13, IL-15, IL-16, IL-17 and interferon (IFN)-γ, while T. tonsurans infection upregulated only a few genes, such as those encoding IL-1β and IL-16. RT-PCR demonstrated that infection by both dermatophytes enhanced IL-8 mRNA expression in keratinocytes. These results suggest that A. benhamiae-induced secretion of several cytokines from keratinocytes may be involved in a severe inflammatory response, and that the limited cytokine secretion from keratinocytes in response to T. tonsurans infection may result in a minimal inflammatory response in the skin. These cytokine profiles may aid in proving the clinical features of dermatophytosis.

The biological effects of syngeneic and allogeneic cytokine-expressing prophylactic whole cell vaccines and the influence of irradiation in a murine melanoma model

Allogeneic whole tumour cell vaccines are inherently practical compared with autologous vaccines. Cell lines are derived from allogeneic tumour, grown in bulk and then administered as a vaccine to the patient, following irradiation, which not only prevents any replication but also enhances antigen presentation. Protection is believed to occur through the presentation of antigens shared between the syngeneic and allogeneic tumours. Although cytokine-transfected tumour whole cell vaccines have been used clinically, little data is available comparing the effects of immunomodulatory cytokine-transfection directly on the same cells when used as both an allogeneic and autologous vaccine. To address this, weakly immunogenic B16-F10 (H-2b) murine melanoma was transfected to secrete either GM-CSF, IL-4 or IL-7. Prophylactic vaccination of both syngeneic C57/BL6 (H-2b) (B6) and allogeneic C3H/Hej (H-2k) (C3H) mice showed the effects of transfected cytokine varied between models. Both GM-CSF and IL-7 significantly (P<0.05) increased the levels of protection within syngeneic B6 mice, but had a diminished effect (P>0.05) within C3H allogeneic mice. Allogeneic B16-F10 cells and syngeneic K1735 cells generated CTL against K1735 suggesting cross-reactive immunity. Using cells labeled with fluorescent dye we demonstrate that irradiated vaccines, of either syngeneic or allogeneic origin, appear to generate potent immune responses and fragments of either vaccine remain at the injection site for up to 9 days. This study shows that protection can be enhanced in vivo by using transfected cytokine, but suggests that irradiated whole cell vaccines, of either tissue-type, are rapidly processed. This leads to the conclusion that the cytokine effects are transient and thus transfection with cytokine may be of limited long-term use in situ.

Skin-derived interleukin-7 contributes to the proliferation of lymphocytes in cutaneous T-cell lymphoma

Cutaneous T-cell lymphomas (CTCLs) are malignancies of T cells that have a special affinity for the skin. We have previously reported that much of the T-cell receptor repertoire is altered in CTCL, and both malignant and nonmalignant clones are numerically expanded, presumably in response to T-cell trophic cytokines. We therefore examined levels of the T-cell trophic cytokines IL-2, IL-4, IL-7, IL-12, IL-13, and IL-15 in plasma in 93 CTCL patients and healthy controls. Only IL-7 levels were elevated in CTCL. We next looked at lesional skin from patients with CTCL and found elevated levels of IL-7 mRNA. Explant cultures of normal and lesional CTCL skin biopsies revealed significantly more IL-7 protein production in CTCL skin. Additionally, cultures of CTCL skin released greater numbers of T cells than normal skin; this was blocked by the addition of an IL-7 neutralizing antibody. Finally, these cultures induced proliferation of normal peripheral skin-homing T cells that were added to the cultures. These observations led us to postulate that IL-7 produced by skin cells contributes to the survival and proliferation of T cells within skin lesions and is likely the source of elevated circulating IL-7 in CTCL.

IL-7 receptor is present on human microvascular endothelial cells

Interleukin-7 (IL-7) is a pleiotropic, non-redundant cytokine crucial for development of B and T lymphocytes. The cellular response to IL-7 is triggered by binding of the cytokine to its receptor, IL-7R. Until now the expression of the receptor was evidenced only in lymphoid and myeloid cell lineages. The receptor consists of two chains: IL-7 specific alpha chain (CD127) and the common gamma(c) chain (CD132) which is a component of several other cytokine receptors: IL-2, IL-4, IL-9 and IL-15. The former observation that exogenous IL-7 is biologically active towards murine endothelial cell lines from secondary lymphoid organs was the starting point of our studies. This observation has prompted us to search for the presence of IL-7 receptor in human microvascular endothelial cells. We used in our studies a set of human endothelial cell lines established from various organs. Our results demonstrate the presence of IL-7R in human microvascular endothelial cells, mainly in the mesenteric but also in the peripheral and to a lesser extent, in the mucosa-associated lymph node endothelial cells. On the basis of the RT-PCR reaction, molecular weight estimated in Western blot and IL-7 binding activity the identified endothelial IL-7 receptor was identical to the lymphocyte-type IL7-R.

Increased interleukin-7 levels in the sera of psoriatic patients: lack of correlations with interleukin-6 levels and disease intensity

Interleukin (IL)-7 is a multifunctional cytokine which is involved in the regulation of keratinocyte-T lymphocyte interactions; the latter is an important factor in the pathogenesis of psoriasis. In vitro, IL-7 is able to induce release of cytokines, including IL-6; IL-6 expression is known to be enhanced in psoriatic patients. Serum levels of IL-7 and IL-6 were measured by ELISA in 40 psoriatic patients and compared with cytokine levels in 18 healthy individuals. Serum levels of IL-7 were also evaluated in 24 psoriatic patients during the remission of the disease after effective treatment. The IL-7 and IL-6 serum levels were significantly higher in psoriatic patients than in healthy subjects and the IL-7 serum levels did not significantly decrease after treatment. Serum levels of IL-7 did not correlate with PASI scores; however, a significant positive relationship was observed between IL-6 levels and PASI scores. There was no correlation between increased levels of IL-7 and IL-6 in the sera of psoriatic patients, suggesting the lack of a direct link between these two cytokines in the psoriatic process. In conclusion, increased IL-7 serum levels suggest that IL-7, like IL-6, may be involved in the pathogenesis of psoriasis, but in contrast with IL-6, serum IL-7 levels could not be used as a marker of disease activity in psoriatic patients.

Dermal Endothelial Cells and Keratinocytes Produce IL-7 In Vivo After Human Schistosoma mansoni Percutaneous Infection

The parasite Schistosoma mansoni infects its definitive mammalian host through an obligatory cutaneous penetration. In this work, we studied early immune response following migration of larvae through human skin, the first immunocompetent organ encountered by the parasite. For this purpose we used an experimental model of severe combined immunodeficient mice engrafted with human skin and injected with autologous PBL. Six days after percutaneous infection, we observed an infiltration of lymphocytes within the human skin, predominantly composed of CD4+ T cells. Moreover, among the cytokines potentially present in the infected skin, immunohistochemistry analysis revealed an in vivo expression of IL-7 in the epidermal layers and strikingly at the level of vascular endothelium. Using an in vitro coculture system, we showed that the S. mansoni larvae directly trigger IL-7 production by human dermal microvascular endothelial cells but not by keratinocytes. Finally, measurements of IL-7 concentrations in plasma of 187 S. mansoni-infected individuals showed that the youngest, which are also the most infected, displayed the highest IL-7 levels. Together, these findings describe dermal endothelial cells as a novel source of IL-7, a cytokine particularly important in schistosomiasis.