Interleukin-15 mRNA is expressed by human keratinocytes Langerhans cells, and blood-derived dendritic cells and is downregulated by ultraviolet B radiation

JAK-STAT pathway inhibitors in dermatology

The JAK-STAT signaling pathway mediates important cellular processes such as immune response, carcinogenesis, cell differentiation, division and death. Therefore, drugs that interfere with different JAK-STAT signaling patterns have potential indications for various medical conditions. The main dermatological targets of JAK-STAT pathway inhibitors are inflammatory or autoimmune diseases such as psoriasis, vitiligo, atopic dermatitis and alopecia areata; however, several dermatoses are under investigation to expand this list of indications. As JAK-STAT pathway inhibitors should gradually occupy a relevant space in dermatological prescriptions, this review presents the main available drugs, their immunological effects, and their pharmacological characteristics, related to clinical efficacy and safety, aiming to validate the best dermatological practice.

A Comprehensive Assessment of the Biocompatibility and Safety of Diamond Nanoparticles on Reconstructed Human Epidermis

Diamond nanoparticles, also known as nanodiamonds (NDs), exhibit remarkable, awe-inspiring properties that make them suitable for various applications in the field of skin care products. However, a comprehensive assessment of their compatibility with human skin, according to the irritation criteria established by the Organization for Economic Cooperation and Development (OECD), has not yet been conducted. The purpose of this study was to evaluate if diamond nanoparticles at a concentration of 25 μg/mL, incubated with reconstituted human epidermis (EpiDermTM) for 18 h, conform to the OECD TG439 standard used to classify chemical irritants. For this purpose, a cell viability test (MTT assay), histological assessment, and analysis of pro-inflammatory cytokine expression were performed. The results indicated that NDs had no toxic effect at the tested concentration. They also did not adversely affect tissue structure and did not lead to a simultaneous increase in protein and mRNA expression of the analyzed cytokines. These results confirm the safety and biocompatibility of NDs for application in skincare products, thereby creating a wide range of possibilities to exert an impact on the advancement of contemporary cosmetology in the future.

Molecular characterization and expression analysis of interleukin-15 (IL-15) genes in orange-spotted grouper (Epinephelus coioides) in response to Vibrio harveyi challenge

As a member of the γc family, interleukin 15 plays an important function in the immune response. In this study, we cloned an IL15 from Epinephelus coioides (named Ec-IL15). The open reading frame of Ec-IL15 is 528 bp, encoding 175 amino acids. Sequence alignment analysis showed that EcIL-15 has a conserved Pfam: IL15 domain and four cysteine residues. Subcellular localization studies have shown that Ec-IL15 is distributed in whole cells. In healthy groupers, Ec-IL15 was expressed in all 11 tissues tested and the highest in liver. After ConA, PHA, LPS and poly I:C stimulation, Ec-IL15 expression of HKLs was significantly upregulated. After V. harveyi infection, the expression of Ec-IL15 in 9 tissues was significantly upregulated and peaked within 48 h. In addition, recombinant Ec-IL15 protein can not only stimulate HKLs proliferation and cytokine expression, but also has the potential as an immune enhancer.

Dynamics of IL-15/IL-15R-α expression in response to HSV-1 infection reveal a novel mode of viral immune evasion counteracted by iNKT cells

Herpes simplex virus type 1 (HSV-1) infects and persists in most of the human population. Interleukin-15 (IL-15) has an important role in the activation of cell-mediated immune responses and acts in complex with IL-15 receptor alpha (IL-15R-α) through cell surface transpresentation. Here, we have examined the IL-15/IL-15R-α complex response dynamics during HSV-1 infection in human keratinocytes. Surface expression of the IL-15/IL-15R-α complex rapidly increased in response to HSV-1, reaching a peak around 12 h after infection. This response was dependent on detection of viral replication by TLR3, and enhancement of IL15 and IL15RA gene expression. Beyond the peak of expression, levels of IL-15 and IL-15R-α gradually declined, reaching a profound loss of surface expression beyond 24 h of infection. This involved the loss of IL15 and IL15RA transcription. Interestingly, invariant natural killer T (iNKT) cells inhibited the viral interference with IL-15/IL-15R-α complex expression in an IFNγ-dependent manner. These results indicate that rapid upregulation of the IL-15/IL-15R-α complex occurs in HSV-1 infected keratinocytes, and that this response is targeted by viral interference. Shutdown of the IL-15 axis represents a novel mode of HSV-1 immune evasion, which can be inhibited by the host iNKT cell response.

The Modulatory Influence of Plant-Derived Compounds on Human Keratinocyte Function

The plant kingdom is a rich source of secondary metabolites with numerous properties, including the potential to modify keratinocyte biology. Keratinocytes are important epithelial cells that play a protective role against various chemical, physical and biological stimuli, and participate in reactive oxygen scavenging and inflammation and wound healing processes. The epidermal cell response may be modulated by phytochemicals via changes in signal transduction pathways. Plant extracts and single secondary compounds can possess a high antioxidant capacity and may suppress reactive oxygen species release, inhibit pro-apoptotic proteins and apoptosis and activate antioxidant enzymes in keratinocytes. Moreover, selected plant extracts and single compounds also exhibit anti-inflammatory properties and exposure may result in limited production of adhesion molecules, pro-inflammatory cytokines and chemokines in keratinocytes. In addition, plant extracts and single compounds may promote keratinocyte motility and proliferation via the regulation of growth factor production and enhance wound healing. While such plant compounds may modulate keratinocyte functions, further in vitro and in vivo studies are needed on their mechanisms of action, and more specific toxicity and clinical studies are needed to ensure their effectiveness and safety for use on human skin.

Oxytocin and positive couple interaction affect the perception of wound pain in everyday life

A large body of animal and human laboratory research has linked social interaction and support to pain perception, with a possible role for the neuropeptide oxytocin as a neuroendocrine mediator. However so far, it has been unclear whether these effects translate to ecologically valid everyday life behavior and pain perception. In a randomized placebo-controlled study, a standard suction blister skin wound was induced to N = 80 romantic couples (N = 160 individuals). Couples then received intranasal oxytocin or placebo twice daily and were either instructed to perform a positive social interaction (partner appraisal task, PAT) once in the laboratory and two times during the following five days, or not. During these days, all participants reported their subjective pain levels multiple times a day using ecologically momentary assessment. Results from hierarchical linear modeling suggest that pain levels within the couples were inter-related. In men, but not in women, oxytocin reduced pain levels. Women reported lower pain levels in the group of positive social interaction, while this effect did not show in men. These results suggest that intranasal oxytocin might have sex-specific effects with pain reducing effects in men but the opposite effects in women. In contrast, especially women benefit from positive interaction in terms of dampened pain levels after positive interaction. The results add to the evidence for health-beneficial effects of positive couple interaction and point to underlying neuroendocrine mechanisms in everyday life pain specifically. The sex-specific effects, in particular, may have implications for psychopharmacological treatment of pain in men and women.

IL-15 Expression Pattern in Atopic Dermatitis

BACKGROUND

An increased expression of interleukin (IL)-15, a cytokine with a key role in stimulating innate and adaptive immune cells, such as dendritic cells (DC), natural killer cells, and T cells, has been observed in infectious and inflammatory diseases, including autoimmune diseases as well as cancer. Atopic dermatitis (AD) is a common inflammatory skin disease characterized by a type 2 immune response.

OBJECTIVE

To explore the expression of IL-15 and its pattern in AD skin.

METHOD

Immunofluorescence staining was performed on skin specimens of AD skin, nonlesional AD skin (AD NL), and normal skin (NS) using antibodies directed against IL-15 and CD3, mast cell tryptase, eosinophil cationic protein, CD68, CD11b, CD1a, and vimentin.

RESULTS

A significantly higher IL-15 expression in AD and AD NL was observed in both the epidermis (p = 0.0003) and the dermis (p = 0.0154) as compared to NS. Cells expressing IL-15 were mainly keratinocytes, CD1a+ DC, CD11b+ DC, CD68+ macrophages, and vimentin+ fibroblasts. In AD, an increase in the relative numbers of IL-15 expressing CD1a+ DC, macrophages, and fibroblasts was noted.

CONCLUSION

Our results demonstrate an expression of IL-15 in AD similar to that of eosinophilic esophagitis which is also a type 2 disease. IL-15 may serve as a therapeutic target for AD.

The Role of Memory CD8+ T Cells in Vitiligo

Vitiligo is an autoimmune skin disease mediated by autoreactive CD8⁺ T cells that destroy the pigment-producing cells of the epidermis, melanocytes, leading to areas of depigmentation. Patients with vitiligo require lifelong treatment to regain and maintain their pigment. Clinical observations uncovered the importance of autoimmune memory in vitiligo because cessation of treatment frequently led to relapse of disease at the site of previous lesions. A subset of memory T cells known as CD8⁺ resident memory T cells (T_RM) are long-lived, nonmigratory memory cells that persist in most nonlymphoid tissues, including the skin. Recent reports describe the presence of CD8⁺ T_RM in lesional vitiligo patient skin and suggest their role as active players in disease maintenance. In this review, we will discuss the role of skin CD8⁺ T_RM in maintaining disease in vitiligo and the opportunity to target this population to induce a long-lasting reversal of disease.

NKG2D Defines a Subset of Skin Effector Memory CD8 T Cells with Proinflammatory Functions in Vitiligo

Vitiligo is an autoimmune disease that results from the loss of melanocytes, associated with skin infiltration of CD8⁺ effector memory T cells with a Tc1 skewed immune response. NKG2D is an activating receptor found on immune cells, in particular natural killer and activated CD8⁺ T cells, that are able to produce a high amount of IFN-γ. Here we found that NKG2D expression was increased in vitiligo skin CD8⁺ effector memory T cells and was promoted by IL-15. Phenotypic and functional analyses showed that NKG2D⁺ CD8⁺ skin effector memory T cells displayed an activated phenotype and produced elevated levels of both IFN-γ and tumor necrosis factor-α. Additional experiments revealed that vitiligo skin dendritic cells expressed the NKG2D ligands MICA-MICB, and in vitro experiments showed that these ligands could be induced on dendritic cells by IFN-α. Cultures of IFN-α-stimulated dendritic cells with skin NKG2D⁺ CD8⁺ T cells potentiated the production of type 1 cytokines, which was next inhibited by blocking the NKG2D/MICA-MICB interaction. These data show that NKG2D is a potential marker of pathogenic skin CD8⁺ effector memory T cells during vitiligo. Therefore, targeting NKG2D could be an attractive strategy in vitiligo, a disease for which there is a strong need of innovative treatments.

Antibody blockade of IL-15 signaling has the potential to durably reverse vitiligo

Vitiligo is an autoimmune disease of the skin mediated by CD8⁺ T cells that kill melanocytes and create white spots. Skin lesions in vitiligo frequently return after discontinuing conventional treatments, supporting the hypothesis that autoimmune memory is formed at these locations. We found that lesional T cells in mice and humans with vitiligo display a resident memory (T_RM) phenotype, similar to those that provide rapid, localized protection against reinfection from skin and mucosal-tropic viruses. Interleukin-15 (IL-15)-deficient mice reportedly have impaired T_RM formation, and IL-15 promotes T_RM function ex vivo. We found that both human and mouse T_RM express the CD122 subunit of the IL-15 receptor and that keratinocytes up-regulate CD215, the subunit required to display the cytokine on their surface to promote activation of T cells. Targeting IL-15 signaling with an anti-CD122 antibody reverses disease in mice with established vitiligo. Short-term treatment with anti-CD122 inhibits T_RM production of interferon-γ (IFNγ), and long-term treatment depletes T_RM from skin lesions. Short-term treatment with anti-CD122 can provide durable repigmentation when administered either systemically or locally in the skin. On the basis of these data, we propose that targeting CD122 may be a highly effective and even durable treatment strategy for vitiligo and other tissue-specific autoimmune diseases involving T_RM.

IL-15 is a component of the inflammatory milieu in the tumor microenvironment promoting antitumor responses

Previous studies have provided evidence that IL-15 expression within human tumors is crucial for optimal antitumor responses; however, the regulation of IL-15 within the tumor microenvironment (TME) is unclear. We report herein, in analyses of mice implanted with various tumor cell lines, soluble IL-15/IL-15Rα complexes (sIL-15 complexes) are abundant in the interstitial fluid of tumors with expression preceding the infiltration of tumor-infiltrating lymphocytes. Moreover, IL-15 as well as type I IFN, which regulates IL-15, was required for establishing normal numbers of CD8 T cells and natural killer cells in tumors. Depending on tumor type, both the tumor and the stroma are sources of sIL-15 complexes. In analyses of IL-15 reporter mice, most myeloid cells in the TME express IL-15 with CD11b⁺Ly6C^hi cells being the most abundant, indicating there is a large source of IL-15 protein in tumors that lies sequestered within the tumor stroma. Despite the abundance of IL-15-expressing cells, the relative levels of sIL-15 complexes are low in advanced tumors but can be up-regulated by local stimulator of IFN genes (STING) activation. Furthermore, while treatment of tumors with STING agonists leads to tumor regression, optimal STING-mediated immunity and regression of distant secondary tumors required IL-15 expression. Overall, our study reveals the dynamic regulation of IL-15 in the TME and its importance in antitumor immunity. These findings provide insight into an unappreciated attribute of the tumor landscape that contributes to antitumor immunity, which can be manipulated therapeutically to enhance antitumor responses.

Weakened IL-15 Production and Impaired mTOR Activation Alter Dendritic Epidermal T Cell Homeostasis in Diabetic Mice

Diabetes is associated with impaired wound healing, which may be caused primarily by a deficiency in dendritic epidermal T cells (DETCs). In the epidermis, IL-15, IGF-1, and mTOR are known to regulate the maintenance of DETCs; however, it is unclear how these molecules may intersect to regulate DETC homeostasis in diabetes. Here, we show that the reduction of DETCs in the epidermis of diabetic mice is caused by altered homeostasis mediated by a reduction in IL-15 levels. Both impaired mTOR activation and reduction of IL-15 in the epidermis play important roles in DETC homeostasis. Moreover, IGF-1 drives keratinocytes to produce IL-15. The activation of IL-15 is dependent on mTOR, and conversely, mTOR regulates IGF-1 production in DETC, in a classic feedback regulatory loop. Our data suggest that in the setting of diabetes, reduced IGF-1, impaired mTOR pathway activation and reduced IL-15 in the epidermis function coordinately to promote altered DETC homeostasis and delayed skin wound closure.

The clinical significance and impact of interleukin 15 on keratinocyte cell growth and migration

Chronic wounds represent a significant burden to health services and are associated with patient morbidity. Novel methods to diagnose and/or treat problematic wounds are needed. Interleukin (IL)-15 is a cytokine involved in a number of biological processes and disease states such as inflammation, healing and cancer progression. The current study explores the expression profile of IL-15 and IL-15 receptor α (IL-15Rα) in chronic wounds and its impact on keratinocytes. IL-15 and IL-15Rα expression were examined in healing and non-healing chronic wounds using qPCR and immunohistochemical analysis. The impact of recombinant IL-15 (rhIL-15) on human adult low calcium temperature (HaCaT) keratinocyte growth and migratory potential was further examined. IL-15 transcript expression was slightly, though non-significantly elevated in healing chronic wounds compared with non-healing chronic wounds. IL-15 protein staining was minimal in both subtypes of chronic wounds. By contrast, IL-15Rα transcript and protein expression were both observed to be enhanced in non-healing chronic wounds compared with healing chronic wounds. The treatment of HaCaT cells with rhIL-15 generally enhanced cell growth and promoted migration. Analysis with small molecule inhibitors suggested that the pro-migratory effect of rhIL-15 may be associated with ERK, AKT, PLCγ and FAK signalling. IL-15 may promote healing traits in keratinocytes and the differential expression of IL-15Rα is observed in chronic wounds. Together, this may imply a complex role for this interleukin in wound healing.

Homeostatic cytokines in immune reconstitution and graft-versus-host disease

For numerous patients, allogeneic stem cell transplantation (SCT) is the only therapeutic option that could potentially cure their disease. Despite significant progress made in clinical management of allogeneic SCT, acute graft-versus-host disease (aGVHD) remains the second cause of death after disease recurrence. aGVHD is highly immunosuppressive and the adverse effect of allogeneic SCT on T cell regeneration is typically more important than the levels of immunosuppression normally seen after autologous SCT. In these patients, immune reconstitution often takes several years to occur and restoring immunocompetence after allogeneic SCT represents an important challenge, principally because clinical options are limited and current methods used to accelerate immune reconstitution are associated with increased GVHD. Interleukin-7 and IL-15 are both under clinical investigation and demonstrate the greatest potential on peripheral T cells regeneration in mice and humans. However, awareness has been raised about the use of IL-7 and IL-15 after allogeneic SCT with regards to potential adverse effects on aGVHD. In this review, we will discuss about recent progress made in lymphocyte regeneration, the critical role played by IL-7 and IL-15 in T cell homeostasis and how these cytokines could be used to improve immune reconstitution after allogeneic SCT.

Molecular pathways: interleukin-15 signaling in health and in cancer

Interleukin-15 (IL-15) is a proinflammatory cytokine involved in the development, survival, proliferation, and activation of multiple lymphocyte lineages utilizing a variety of signaling pathways. IL-15 utilizes three distinct receptor chains in at least two different combinations to signal and exert its effects on the immune system. The binding of IL-15 to its receptor complex activates an "immune-enhancing" signaling cascade in natural killer cells and subsets of T cells, as well as the induction of a number of proto-oncogenes. Additional studies have explored the role of IL-15 in the development and progression of cancer, notably leukemia of large granular lymphocytes, cutaneous T-cell lymphoma, and multiple myeloma. This review provides an overview of the molecular events in the IL-15 signaling pathway and the aberrancies in its regulation that are associated with chronic inflammation and cancer. We briefly explore the potential therapeutic opportunities that have arisen as a result of these studies to further the treatment of cancer. These involve both targeting the disruption of IL-15 signaling as well as IL-15-mediated enhancement of innate and antigen-specific immunity.

A promoter polymorphism (rs3806798) of interleukin-15 gene is associated with chronic hepatitis B virus infection in the Chinese Han population

This study aimed to investigate the association between the polymorphisms of IL-15 gene and susceptibility to chronic hepatitis B virus (HBV) infection in the Chinese Han population. A total of 234 patients with chronic HBV infection and 150 age- and sex-matched healthy controls in the Chinese population were enrolled in this case-control study. Genotyping of ten single nucleotide polymorphisms (SNPs) in the IL-15 gene was carried out via Sequenom MassARRAY system. The association analysis demonstrated that SNP rs3806798 (A/T) had a significant difference in the distribution between patients and healthy controls (P = 0.033). Moreover, a significantly increased risk of HBV infection was found to be associated with IL-15 rs3806798 A allele among male patients and HBeAg-negative patients, compared with IL-15 rs3806798 T allele (P = 0.003; P = 0.046, respectively). Furthermore, haplotype analysis revealed that haplotype ATAGG (rs3806798, rs12508866, rs1519551, rs6819823 and rs2857261, respectively) in block 1 was significantly associated with HBV infection (P = 0.022). In conclusion, we found an association between IL-15 rs3806798 and the risk of chronic HBV infection in a sample of Chinese Han population.

Potential efficacy of imiquimod on immunity-related cytokines in murine skin in vivo and in human Langerhans cells in vitro

INTRODUCTION

Imiquimod, an immune-response modifier, has been proven to be clinically effective in the treatment of viral infections and skin cancers, but its mechanism of action remains poorly understood. This study aimed to assess the effects of imiquimod on the expression of three immunity-related cytokines, TNF-α, IL-1β, and IL-6.

MATERIALS AND METHODS

Female BALB/C mice were treated for seven days with topical 1% imiquimod cream; they were then killed and skin samples were snap-frozen. In the in vitro studies, both purified LCs and HaCaT cells were incubated with 5 μg/ml imiquimod for four hours. In all samples, the mRNA levels of TNF-α, IL-1β, and IL-6 were then detected by reverse transcription polymerase chain reaction, and the secretion levels were determined by an enzyme-linked immunosorbent assay.

RESULTS

Imiquimod upregulated the mRNA and protein expression levels of TNF-α, IL-1β, and IL-6 in the skin of imiquimod-treated BALB/C mice and in human LCs, compared with untreated controls (P<0.05). However, there was no significant difference in the expression of these cytokines in imiquimod-treated and untreated HaCaT cells.

CONCLUSIONS

These findings indicate that imiquimod increased the expression of TNF-α, IL-1β, and IL-6 in skin and that the target cell of imiquimod may be the LCs but is unlikely to be the epidermal keratinocytes.

Immune functions of the skin

The skin, the body's largest organ, helps to secure the integrity of the host and, at the same time, allows the individual to communicate with the outside world. This finely tuned balance between protection from harmful pathogens (mostly microorganisms) and bidirectional signal exchange is provided by a network of structural, cellular, and molecular elements that are collectively referred to as the skin barrier. This "gateway" has a physical, chemical, and immunologic component. The role of the latter is to elicit a powerful defense reaction in the case of danger and, at the same time, to prevent such a reaction against innocuous substances. Immune responses originating in the skin are mounted and executed by cells and molecules of the innate or the adaptive immune system. Innate reactions are typically rapid, poorly discriminating, and do not exhibit memory. Adaptive responses, in contrast, show a high degree of specificity as well as memory but need a protracted time for their development. As a consequence, innate and adaptive responses are consecutive events influencing each other. In fact, we now know that the type and magnitude of the innate reactions govern and often determine the quality and quantity of adaptive responses.

Novel gamma-chain cytokines as candidate immune modulators in immune therapies for cancer

Cytokines that signal through the common-gamma chain are potent growth factors for T cells and natural killer cells. Interleukin (IL)-2, the gammac prototype, can mediate antitumor effects as a single agent or in the context of multimodality regimens but is limited by side effects and a propensity for expansion of regulatory T cells. IL-7, IL-15, and IL-21 each possess properties that can be exploited in the context of immunotherapy for cancer. Each has been demonstrated to mediate potent vaccine adjuvant effects in tumor models, and each can enhance the effectiveness of adoptive immunotherapies. Although the overlap among the agents is significant, IL-7 is uniquely immunorestorative and preferentially augments reactivity of naive populations, IL-15 potently augments reactivity of CD8 memory cells and natural killer cells, and IL-21 preferentially expands the inflammatory Th17 subset and may limit terminal differentiation of effector CD8 cells. Clinical trials of IL-7 and IL-21 have already been completed and, so far, demonstrate safety and biologic activity of these agents. Clinical trials of IL-15 are expected soon. Ultimately, these agents are expected to be most effective in the context of multimodal immunotherapy regimens, and careful clinical trial design will be needed to efficiently identify the proper doses, regimens, and settings in which to exploit their biologic properties for therapeutic gain.

Interleukin-15 enhances proliferation and chemokine secretion of human follicular dendritic cells

The germinal centre (GC) is a specialized microenvironment where high-affinity antibodies are produced through hypermutation and isotype switching. Follicular dendritic cells (FDCs) are the stromal cells of the GC. The timely expansion and establishment of an FDC network is essential for a protective GC reaction; however, only a few factors modulating FDC development have been recognized. In this study, we report that interleukin-15 (IL-15) enhances human primary FDC proliferation and regulates cytokine secretion. The FDCs express IL-15 receptor complexes for IL-15 signal transduction as well as for specific binding. Moreover, the secretion of chemokines CCL-2, CCL-5, CXCL-5 and CXCL-8 was reduced by blocking IL-15 signalling while the secretion of other cytokines, and the expression of CD14, CD44, CD54 (ICAM-1) and CD106 (VCAM-1) proteins remained unchanged. These results suggest that IL-15 plays a crucial role in the development of FDC networks during GC reaction, offering a new target for immune modulation.

In vivo role of Flt3 ligand and dendritic cells in NK cell homeostasis

IL-15 is required for NK cell development and homeostasis in vivo. Because IL-15 is presented in trans via its high-affinity IL-15Ralpha-chain to cells expressing the IL-15Rbetagamma complex, we postulated that certain IL-15-bearing cells must be required for NK cell homeostasis. Using IL-15(WT/WT) and IL-15(-/-) mice, bone marrow chimeras with normal cellularity, and a selective depletion of CD11c(hi) dendritic cells (DCs), we demonstrate that ablation of the resting CD11c(hi) DC population results in a highly significant decrease in the absolute number of mature NK cells. In contrast, administration of Flt3 ligand increases the CD11c(hi) DC population, which, when expressing IL-15, significantly expands mature NK cells via enhanced survival and proliferation. In summary, a CD11c(hi) DC population expressing IL-15 is required to maintain NK cell homeostasis under conditions of normal cellularity and also is required to mediate Flt3 ligand-induced NK cell expansion in vivo.

Interleukin-15 and NK1.1+ cells provide innate protection against acute Salmonella enterica serovar Typhimurium infection in the gut and in systemic tissues

Control of bacterial colonization at mucosal surfaces depends on rapid activation of the innate immune system. Interleukin-15 (IL-15) directs the development, maturation, and function of a population of cells positive for NK1.1, such as natural killer (NK) cells, which are critical components of the innate immune defense against several viral and bacterial pathogens. Using IL-15-deficient mice, in vivo depletion of NK1.1(+) cells from wild-type mice, and in vivo overexpression of IL-15 from a recombinant adenovirus, we tested the role of IL-15 and NK1.1(+) cells in innate protection of the murine gut and reticuloendothelial system from Salmonella enterica serovar Typhimurium infection. IL-15 and the NK1.1(+) cell population provided innate protection from serovar Typhimurium in mice at the enteric mucosae and in the reticuloendothelial system during murine typhoid. Interestingly, serovar Typhimurium extensively colonized the gut of IL-15(-/-) mice and wild-type C57BL/6 mice depleted of NK1.1(+) cells prior to infection, even though the animals were not pretreated with antibiotics to reduce colonization resistance and there was an absence of overt inflammation in the colon and cecum. Enhanced dissemination of Salmonella from the gut of mice depleted of NK1.1(+) cells correlated with a localized disruption of IL-17 in the colon. These data suggest a relationship between the gut ecosystem and the innate mucosal immune system, which may be linked via IL-15 and NK1.1(+) cells.

Cytokines and anticytokines in psoriasis

BACKGROUND

Psoriasis is a chronic autoimmune hyperproliferative skin disease of varying severity affecting approximately 2-3% of the general population in the USA and Europe. Although the pathogenesis of psoriasis has not been fully elucidated, an immunologic-genetic relationship is likely. Cutaneous and systemic overexpression of various proinflammatory cytokines (TNF, interleukins, interferon-gamma) has been demonstrated in psoriatic patients.

METHODS

We reviewed the current database literature and summarized the involvement of cytokines and their receptors in the pathogenesis and treatment of psoriasis.

RESULTS

Although many cytokine/anti-cytokine therapies have been conducted, TNF antagonists in the treatment of both psoriasis arthropatica and vulgaris appear to be the most widely used clinically. Interestingly, the efficacy and tolerability of some cytokines (rhIL-11 or ABX-IL-8,) were found to be much lower than expected.

CONCLUSIONS

Preliminary results obtained with cytokine and anti-cytokine therapies appear promising and as such continued research is clearly indicated.

Arsenic trioxide down-regulates antiapoptotic genes and induces cell death in mycosis fungoides tumors in a mouse model

BACKGROUND

Mycosis fungoides (MF) is the most frequent cutaneous T-cell lymphoma (CTCL). Arsenic trioxide (As(2)O(3)) has recently been shown to be effective against leukemias, so we studied whether As(2)O(3) induces apoptosis of CTCL cells in vitro. We further investigated if As(2)O(3) is effective in a MF mouse model.

MATERIAL AND METHODS

Annexin V/7-amino-actinomycin-D stainings were carried out to investigate if As(2)O(3) induced apoptosis of CTCL cell lines. To study the underlying mechanisms, the effects of As(2)O(3) on various transcription factors and apoptosis regulating proteins were analyzed by western blots, electrophoretic mobility shift assays and transcription factor enzyme-linked immunosorbent assays. The ability of As(2)O(3) to induce tumor regression was investigated in a MF mouse model.

RESULTS

As(2)O(3)-induced apoptosis was paralleled by a reduction of the DNA-binding activities of transcription factors of the NFkB and signal transducer and activator of transcription gene families and reduced expression of the antiapoptotic proteins bcl-1, bcl-xL and mcl-1. Local injections of 200 muM As(2)O(3) into tumors caused complete remissions in five of six mice and one partial remission.

CONCLUSIONS

As(2)O(3) induced apoptosis of CTCL cells by the down-regulation of transcription factors that stimulate the expression of antiapoptotic genes. Local injection of As(2)O(3) into MF tumor-bearing mice resulted in tumor regression.

Mycosis fungoides and Sézary syndrome

Mycosis fungoides and Sézary syndrome are the most common of the cutaneous T-cell lymphomas, which are a heterogeneous group of neoplasms that affect the skin as a primary site. Although the aetiologies of mycosis fungoides and Sézary syndrome are unknown, important insights have been gained in the immunological and genetic perturbations that are associated with these diseases. Unlike some B-cell lymphomas, cutaneous T-cell lymphomas as a group are rarely if ever curable and hence need chronic-disease management. New approaches to treatments are being investigated and include biological and cytotoxic drugs, phototherapy, and monoclonal antibodies that are directed towards novel molecular targets. New molecular technologies such as complementary-DNA microarray have the potential to increase the accuracy of diagnosis and provide important prognostic information. Treatments can be combined to greatly improve clinical outcome without substantially increasing toxic effects in advanced disease that is otherwise difficult to treat. Although present treatment strategies are generally not curative, there is hope that experimental treatments, particularly immunotherapy, might eventually reverse or suppress the abnormalities of mycosis fungoides and Sézary syndrome to the point at which they become non-life-threatening, chronic diseases.

Molecular and Functional Characterization of IL-15 in Rainbow TroutOncorhynchus mykiss:A Potent Inducer of IFN-γ Expression in Spleen Leukocytes

IL-15 is a member of the common gamma-chain family of cytokines that possess a heterogeneous repertoire of activities on various cells of the immune system. We report here the first functional characterization of a fish IL-15 in rainbow trout. The trout IL-15 gene is 6-kb long and contains six exons and five introns that transcribe into a 1.2-kb mRNA containing seven out-of-frame AUG initiation codons and translate into a 193-aa peptide. Potential sites for transcriptional activators and repressors have been identified in the trout IL-15 gene. Like IL-15 from other species, trout IL-15 is closely linked to an INPP4B gene, but there is also a BCL10 gene located between the IL-15 and INPP4B genes. Three alternative splicing variants of the trout IL-15 gene have also been identified and their expression in vivo was studied. Trout IL-15 expression is present in all the tissues and cell lines studied. Recombinant trout IFN-gamma selectively increased IL-15 expression but had little effect on other cytokines such as IL-1 beta and IL-11. Recombinant trout IL-15 preferentially stimulated splenic leukocytes from healthy fish, where it induced a large increase in IFN-gamma expression, with little, if any, effect on IL-1 beta expression. This effect was quite long-lived, and was still apparent 24 h poststimulation. Although the exact cell types being affected have still to be determined, it is clear that once produced IL-15 will have a profound affect on the ability of the fish immune system to activate antimicrobial defenses and genes induced themselves by IFN-gamma.

Regulation of UVB-Induced IL-8 and MCP-1 Production in Skin Keratinocytes by Increasing Vitamin C Uptake via the Redistribution of SVCT-1 from the Cytosol to the Membrane

It is well known that UVB (290-320 nm) induces inflammation in skin by the transcription and release of cytokines and chemokines from skin keratinocytes. In addition, it is considered that intracellular reactive oxygen species (ROS) plays an important role in UVB-induced inflammatory response in the skin. Therefore, we investigated the effect of vitamin C, a potent antioxidant, on the regulation of UVB-induced skin inflammation via the modulation of chemokines production. Vitamin C uptake into keratinocytes is increased by UVB irradiation in a time- and dose-dependent manner through the translocation of sodium-dependent vitamin C transporter-1 (SVCT-1), a vitamin C-specific transporter, from the cytosol to the membrane. To evaluate the effect of vitamin C on the chemokine mRNA expression, we performed RNase protection assay. As a result, there was a remarkable change in chemokine mRNA expression, especially IL-8 and monocyte chemoattractant protein (MCP)-1 expression. In addition, increased IL-8 and MCP-1 mRNA expressions were suppressed by vitamin C treatment. We also confirmed the results of protein levels measured by ELISA. Taken together, vitamin C uptake is increased in UVB-irradiated keratinocytes through the translocation of SVCT-1 and regulates inflammatory response in the skin via the downregulation of IL-8 and MCP-1 production.

Cutaneous malignant lymphomas: Update 2006

Cutaneous lymphomas represent a unique group of lymphomas and are the second most frequent extranodal lymphomas. As with other neoplasias, the pathogenesis is based mainly on a stepwise accumulation of mutations of suppressor genes and oncogenes caused by genetic, environmental or infectious factors. The diagnostic work-up includes clinical, histological, imaging and hematological investigations and in many cases immunohistochemical and molecular biological analyses. The current WHO/EORTC classification of cutaneous lymphomas differentiates "mature T-cell and NK-cell lymphomas", "mature B-cell lymphomas" and "immature hematopoietic malignancies", their variants and subgroups. It is compatible with the WHO classification for neoplasias of the hematopoietic and lymphoid tissue and respects the organ-specific peculiarities of primary cutaneous lymphomas. The assignment of the various types of cutaneous lymphomas into prognostic categories (pre-lymphomatous "abortive" disorders; definite malignant lymphomas of low-grade malignancy; definite malignant lymphomas of high-grade malignancy) provides essential information on the biological behavior and allows an appropriate planning of the therapeutic strategy, which may be topical or systemic and aggressive or non-aggressive. Besides the classical options for therapy, there are new and "experimental" strategies, the efficacy of which has to be studied in clinical trials.

Severe papillomavirus infection progressing to metastatic squamous cell carcinoma in bone marrow-transplanted X-linked SCID dogs

Canine X-linked severe combined immunodeficiency (XSCID) is due to mutations in the common gamma chain (gammac) gene and is identical clinically and immunologically to human XSCID, making it a true homologue of the human disease. Bone marrow-transplanted (BMT) XSCID dogs not only engraft donor T cells and reconstitute normal T-cell function but, in contrast to the majority of transplanted human XSCID patients, also engraft donor B cells and reconstitute normal humoral immune function. Shortly after our initial report of successful BMT of XSCID dogs, it soon became evident that transplanted XSCID dogs developed late-onset severe chronic cutaneous infections containing a newly described canine papillomavirus. This is analogous to the late-onset cutaneous papillomavirus infection recently described for human XSCID patients following BMT. Of 24 transplanted XSCID dogs followed for at least 1 year post-BMT, 71% developed chronic canine papillomavirus infection. Six of the transplanted dogs that developed cutaneous papillomas were maintained for >3 1/2 years post-BMT for use as breeders. Four of these six dogs (67%) developed invasive squamous cell carcinoma (SCC), with three of the dogs (75%) eventually developing metastatic SCC, an extremely rare consequence of SCC in the dog. This finding raises the question of whether SCC will develop in transplanted human XSCID patients later in life. Canine XSCID therefore provides an ideal animal model with which to study the role of the gammac-dependent signaling pathway in the response to papillomavirus infections and the progression of these viral infections to metastatic SCC.

IL-15 prevents allergic rhinitis through reactivation of antigen-specific CD8+ cells

BACKGROUND

Allergic rhinitis is one of the most common allergic inflammatory diseases characterized by a predominant TH2 response with antigen-specific IgE synthesis. IL-15 plays important roles in activation and maintenance of memory CD8+T cells capable of producing IFN-gamma, which regulates TH2 responses.

OBJECTIVE

To investigate the roles of endogenous IL-15 in allergic inflammation, we examined allergic rhinitis in IL-15 knockout (KO) mice sensitized with ovalbumin followed by intranasal rechallenge with ovalbumin.

METHODS

IL-15KO mice were sensitized intraperitoneally with ovalbumin/complete Freund's adjuvant on day 0 and ovalbumin/IFA on day 7, and then were intranasally challenged with ovalbumin on days 21, 22, 23, 24, and 25. Nasal symptoms and histologic changes were examined. IgE production and TH2 responses were measured by ELISA. Purified CD8+T cells or recombinant IL-15 were administered into ovalbumin-sensitized mice.

RESULTS

The levels of IgE production and TH2 responses in IL-15KO mice were comparable to those in control mice after ovalbumin sensitization. However, sneezing, infiltration of eosinophils into the nasal mucosa, and TH2 cytokine production were aggravated in ovalbumin-sensitized IL-15KO mice after intranasal challenge with ovalbumin. Adoptive transfer of CD8+6 T cells from ovalbumin-sensitized mice suppressed the TH2 responses in mice but not in IL-15KO mice. Administration of IL-15 with ovalbumin significantly prevented the development of allergic rhinitis in ovalbumin-sensitized mice.

CONCLUSION

We demonstrate with IL-15KO mice that endogenous IL-15 plays an important role in suppression of allergic rhinitis at effector phase. Intranasal administration of IL-15 is useful as a therapeutic approach to control allergic rhinitis.

CLINICAL IMPLICATIONS

Intranasal administration of recombinant IL-15 might become new immunotherapy for allergic rhinitis.

Herpesviruses and the innate immune response

Herpesvirus infection leads to the rapid induction of an innate immune response. A central aspect of this host response is the production and secretion of type I interferon. The current model of virus-mediated interferon production includes three stages: sensitization, induction, and amplification. A key mediator of all three stages is the cellular transcription factor interferon regulatory factor 3 (IRF3). Although the precise details of IRF3 activation and interferon production in response to herpesvirus infection are still being elucidated, viral proteins that block components of the interferon pathway, particularly IRF3, have been identified and characterized. In vivo studies have shown that in addition to type I interferon, interleukin-15 (IL-15) and natural killer (NK) cells also play an important role in mediating resistance to herpesvirus infection. Recent investigations have demonstrated a strong association between IRF3, interferon, IL-15, and NK cells. This review will focus on herpesvirus-mediated induction of innate immunity, the central role of the type I interferon response and mechanisms used by herpesviruses to block host antiviral immunity.

Clinical improvement in chronic plaque-type psoriasis lesions after narrow-band UVB therapy is accompanied by a decrease in the expression of IFN-gamma inducers -- IL-12, IL-18 and IL-23

Type-1 cytokine-producing T cells are important in the pathogenesis of psoriasis vulgaris, for which efficient therapy is provided by means of narrow-band ultraviolet-B (NB-UVB). The expression of the type-1 cytokine interferon-gamma (IFN-gamma) is regulated by interleukin-12 (IL-12), IL-15, IL-18 and IL-23; however, not much is known about the effect of this therapy on the levels of these cytokines in lesional psoriatic skin in situ. In this study, we investigated the effects of NB-UVB therapy on the expression of IFN-gamma-inducing cytokines. Ten patients with chronic plaque-type psoriasis selected to be treated with NB-UVB therapy were recruited for these experiments and the expression of cytokines IL-12, IL-15, IL-18, IL-23 and IFN-gamma in lesional psoriatic skin before, during and after therapy was determined with the help of immunohistochemistry. Double staining was performed in order to determine the cell types expressing these cytokines. The decrease in the psoriasis area and severity index was accompanied by a significant decrease in the expression of IFN-gamma, and concomitantly, significant reduction of IFN-gamma inducers -- IL-12, IL-18 and IL-23. Thus, we concluded that the decrease of IFN-gamma expression in psoriasis lesions after NB-UVB therapy could be a result of diminished expression of IL-12, IL-18 and IL-23 in lesional skin. Therapies targeting these three cytokines should, therefore, be considered in the treatment of psoriasis.

Reduced 2,4-dinitro-1-fluorobenzene-induced contact hypersensitivity response in IL-15 receptor??-deficient mice correlates with diminished CCL5/RANTES and CXCL10/IP-10 expression

Using a model of 2,4-dinitro-1-fluorobenzene-induced contact hypersensitivity (CHS) we found that, as compared with wild-type mice, IL-15 receptor alpha chain (IL-15Ralpha)-deficient mice showed significantly less ear swelling. This decreased response was associated with diminished expression of CCL5/RANTES and CXCL10/IP-10, chemokines critical for effector cell recruitment, in the inflamed tissue. We determined that both the number of CD8(+) T cells infiltrating the affected skin and the production of CCL5/RANTES by antigen-stimulated CD8(+) T cells were decreased in IL-15Ralpha(-/-) mice. The lower levels of CXCL10/IP-10 suggested that the IL-15Ralpha(-/-) mice had reduced production of IFN-gamma, the primary inducer of CXCL10/IP-10, which was in fact the case. However, by contrast with CCL5/RANTES, the diminished levels of IFN-gamma were likely due to the decreased number of skin-infiltrating CD8(+) T cells, since IFN-gamma production by antigen-stimulated CD8(+) T cells was comparable between wild-type and IL-15Ralpha(-/-) mice. Our data suggest a positive, pro-inflammatory feedback loop involving CCL5/RANTES, IFN-gamma and CXCL10/IP-10 that underlies the CHS reaction and that is disrupted, likely primarily by a defect in CCL5/RANTES production, in mice lacking IL-15Ralpha, resulting in impaired leukocyte recruitment and inflammation. Moreover, it is particularly noteworthy that the defect in CCL5/RANTES expression in CD8(+) T cells is intrinsic to the absence of IL-15Ralpha, indicating that IL-15Ralpha is critical for CCL5/RANTES expression in CD8(+) T cells.

Mature dendritic cells can enhance CD8+ cell noncytotoxic anti-HIV responses: the role of IL-15

The CD8+ cell noncytotoxic anti-HIV response (CNAR) is associated with a long-term healthy clinical state in HIV-infected individuals. Over time CNAR is reduced concomitant with progression to disease. In studies to evaluate whether the interaction between CD8+ cells and dendritic cells (DCs) could increase CNAR, CD8+ cells from individuals who showed a decrease in this antiviral activity were cocultured with monocyte-derived dendritic cells matured with CD40 ligand. After coculture with these mature DCs, the CD8+ cells showed an increase in CNAR greater than that observed with CD8+ cells costimulated with CD3/CD28 antibodies. This antiviral response appeared to be mediated primarily by production of interleukin-15 (IL-15) by the mature DCs. Purified IL-15 also enhanced CNAR, whereas IL-12 showed no substantial effect. These studies provide another potential approach by which the immune system in HIV infection could be restored by cytokine therapy, particularly IL-15 administration.

Interleukin-15 and natural killer and NKT cells play a critical role in innate protection against genital herpes simplex virus type 2 infection

Interleukin-15 (IL-15), natural killer (NK) cells, and NK T (NKT) cells, components of the innate immune system, are known to contribute to defense against pathogens, including viruses. Here we report that IL-15(-/-) (NK(-) and NKT(-/+)) mice and RAG-2(-/-)/gamma(c)(-/-) (NK(-) and NKT(-)) mice that lack all lymphoid cells were very susceptible to vaginal infection with a low dose of herpes simplex virus type 2 (HSV-2). IL-15(-/-) and RAG-2(-/-)/gamma(c)(-/-) mice were 100-fold more susceptible and RAG-2(-/-), CD-1(-/-) (NKT(-)), and gamma interferon (IFN-gamma)(-/-) mice were 10-fold more susceptible to vaginal HSV-2 infection than control C57BL/6 mice. NK and/or NKT cells were the early source of IFN-gamma in vaginal secretions following genital HSV-2 infection. This study demonstrates that IL-15 and NK-NKT cells are critical for innate protection against genital HSV-2.

Studies on the production of IL-15 in HIV-infected/AIDS patients

IL-15 is essential for the development and differentiation of NK cells. It selectively induces proliferation of CD8+ memory T lymphocytes. Despite its importance in both innate and adaptive immune responses, little is known about its production in HIV-infected persons. We report here that IL-15 levels are significantly decreased in the sera of HIV-infected/AIDS patients compared to control sera. We also show that PBMC from the infected patients are compromised in their ability to respond with enhanced production of IL-15 upon exposure to HSV-1. The decreased production of IL-15 occurs despite a comparable increase in IL-15 mRNA in the PBMC of HIV-infected and healthy HIV-seronegative donors when exposed to HSV-1. The HSV-stimulated patients' PBMC exhibited less NK activity compared to similarly treated normal PBMC. These results suggest that a compromised ability of PBMC from HIV-infected individuals to induce IL-15 production in response to a viral stimulus may be a reason of their compromised innate and adaptive immunity.

IL-15 is a growth factor and an activator of CD8 memory T cells

Memory lymphocytes, arising from naïve lymphocytes after antigenic stimulation and being long-lived, are the cellular basis for immunological memory. Recent studies of CD8 T cells suggest that generation of CD8 memory T cells requires the engagement of T cell antigen receptors (TCR) with antigen, yet the maintenance of CD8 memory T cells appears to be dependent on cytokines, such as IL-15, independent of TCR. Although considerable progress has been made in understanding the molecular and cellular events of TCR-induced differentiation and proliferation in the past decade, less is known about the mechanisms of IL-15 action. From a kinetic and comparative analysis of the responses of memory phenotype CD8 T cells to IL-15 and TCR stimulation in vitro, we found that IL-15 and anti-CD3 induce highly similar responses in memory phenotype CD8 T cells as measured by general gene expression profiles, synthesis of effector molecules (IFNgamma, TNFbeta, granzyme B and perforin), induction of cytotoxicity, and cellular proliferation. These findings indicate that IL-15 is not only a growth factor but also an antigen-independent activator for CD8 memory T cells.

IL-15 induces unspecific effector functions in human peptide-specific CD8+ T-cell cultures

Antigen (Ag)-specific CD8+ T cells are a major host defence against viral infections. In the present study, we generated human CD8+ T-cell lines specific towards influenza matrix peptide (IMP)-pulsed Ag-presenting cells. We compared the effect of interleukin-2 (IL-2) and IL-15 on the proliferation and cytotoxic activity of primary and secondary IMP-specific cytotoxic T lymphocyte (CTL) culture. In primary CTL cultures, IL-15-induced cell expansion was considerably reduced as compared with IL-2-induced cell expansion, and IL-15 favoured the outgrowth of CTLs without peptide specificity in these cultures. Secondary IMP-specific CD8+ T cells were generated by the addition of IL-2 during two cycles of restimulation. From the third restimulation, identical CTL cultures were expanded with either IL-2 or IL-15 in parallel. Cell expansion as well as Ag specificity was considerably reduced after a 5 day culture period in the presence of IL-15. No or low CD69 expression was observed in IL-15-cultured CTLs, whereas IL-2-cultured CTLs contained high fractions of CD69+ cells. Furthermore, a high fraction of these latter cells coexpressed the cytotoxic marker CD56. However, IL-15-cultured CTLs exhibited cytotoxic activity without detectable expression of CD56, suggesting that CD56 is not essential for cytotoxic activity. Thus, the results presented suggest that IL-15 favours the outgrowth of unspecific cytotoxic effector T cells.

Keratinocytes and cytokines

The skin has long been recognized as a major producer of cytokines, but the keratinocyte as principal epidermal cell has received less attention as potential source and target of cytokines. Nevertheless, keratinocytes produce a plethora of cytokines including interleukin (IL)-1, -6, -7, -8, -10, -12, -15, -18, and -20, and tumor necrosis factor alpha (TNF). The production by keratinocytes of pro-inflammatory (IL)-1, -6, -8, and TNF was recognized early and is well studied. Keratinocyte-derived IL-7 and -15 are considered to be significant in T-cell trafficking, possibly even in the pathogenesis of cutaneous T-cell lymphoma. Immunomodulatory IL-10 and -12 originating from keratinocytes are considered to be responsible for systemic effects, and IL-18 perhaps has a similar action. Keratinocytes were fairly recently recognized as being source or target of other IL-10 family members like IL-20 and IL-24 and the role of these cytokines in specific diseases is under investigation. In addition, a variety of cytokine receptors are present on keratinocytes like those for IL-4, -13, and -17 and to lesser degree IL-2. The ability to study the expression of cytokines by keratinocytes in vivo and in vitro using primary cells, immortalized cells or even organotypic culture systems offers many possibilities to further investigate the role of cytokine production in keratinocyte biology and disease.

IL-2-IgG2b fusion protein suppresses murine contact hypersensitivity in vivo

Interleukin-15 shares several functional properties with interleukin-2, and signals through the beta and gamma chain of the interleukin-2 receptor as well as through its own high affinity alpha chain. In agreement with the concept that interleukin-2 plays a key role in type IV immune responses, we have recently shown that an IL-2-IgG2b fusion protein potently suppresses Th1-type delayed type hypersensitivity reaction and Th2-type allergic sensitization in mice. We have now compared the in vivo effects of IL-2-IgG2b fusion protein with those of IL-15-IgG2b fusion protein in a murine model of Th1-type contact hypersensitivity reaction. Daily systemic injections of IL-2-IgG2b fusion protein during the sensitization phase or application of IL-2-IgG2b fusion protein just 2 h before and 10 h after antigen challenge significantly inhibited the contact hypersensitivity ear swelling response, and this without any overt signs of associated toxicity. Even local injection of IL-2-IgG2b fusion protein into the earlobe around the time of antigen challenge inhibited the ear swelling reaction significantly. In contrast, neither systemic nor local injection of the IL-15-IgG2b fusion protein modulated the contact hypersensitivity reaction significantly. IL-2-IgG2b but not IL-15-IgG2b fusion protein reduced migration of antigen-presenting cells from the skin to local lymph nodes, inhibited the expression of CD80 and CD86, and induced a significant higher number of CD4+CD25+ T cells. Therefore, the IL-2-IgGb fusion protein offers a powerful tool for suppressing and/or preventing T-cell-mediated hypersensitivity reaction in vivo.

Quantitation of natural killer cell precursors in man

A technique was developed to measure the frequency of natural killer cell precursors (NKpf) in human peripheral blood mononuclear cell (PBMC) samples. Functional maturity of NK cells was reflected in their ability to lyse target cells from the K562 cell line. During the development of the technique, venous blood was taken from one healthy adult and assayed at different times to avoid individual variation. The technique was based on the principle of limiting dilution analysis. The NKpf assay was set up with a range of cell dilutions from 40,000 to 625 per 100 microl/well in 96-well culture plates. At the end of the culture period, the K562 cell line labelled with europium (Eu-K562) was added and the Eu-release was measured in culture supernatants using time-resolved fluorometry. The NKpf value differed between individuals and was influenced by the length of time in culture, being maximal at day 5. Maturation of NKp required the continuous presence of recombinant interleukin 2 (rIL-2), or rIL-15, both being equally effective. In the absence of cytokines, the functional NK cells declined rapidly beyond 24 h in culture. Irradiated allogeneic cells appeared to substitute in part for cytokines, but the numbers of allo-activated NKpf were lower than those observed when allo-activated NKpf were cultured with rIL-2. This suggested selective activation by the allogeneic stimulus of subsets of NKp or rIL-2-rescue of NKp subsets destined for apoptotic cell death. Alternatively, the increased frequency could have been attributable to activation of precursors of natural killer-T cells (NK-Tp). This assay is suitable for estimating the total number of precursors of functional NK cells in the blood of patients.

Dendritic cells: immune regulators in health and disease

Dendritic cells (DCs) are bone marrow-derived cells of both lymphoid and myeloid stem cell origin that populate all lymphoid organs including the thymus, spleen, and lymph nodes, as well as nearly all nonlymphoid tissues and organs. Although DCs are a moderately diverse set of cells, they all have potent antigen-presenting capacity for stimulating naive, memory, and effector T cells. DCs are members of the innate immune system in that they can respond to dangers in the host environment by immediately generating protective cytokines. Most important, immature DCs respond to danger signals in the microenvironment by maturing, i.e., differentiating, and acquiring the capacity to direct the development of primary immune responses appropriate to the type of danger perceived. The powerful adjuvant activity that DCs possess in stimulating specific CD4 and CD8 T cell responses has made them targets in vaccine development strategies for the prevention and treatment of infections, allograft reactions, allergic and autoimmune diseases, and cancer. This review addresses the origins and migration of DCs to their sites of activity, their basic biology as antigen-presenting cells, their roles in important human diseases and, finally, selected strategies being pursued to harness their potent antigen-stimulating activity.

IL-15-induced conversion of monocytes to mature dendritic cells

IL-15 is produced by a wide variety of tissues in response to inflammatory stimuli. We examined the effect of IL-15 in supporting the maturation of monocytes to dendritic cells in ex vivo culture. IL-15 transformed CD14(+) monocytes to mature dendritic cells. These dendritic cells were similar to those obtained from monocyte cultures treated with a combination of the cytokines GM-CSF, IL-4 and TNF-alpha. The effects of IL-15 did not depend on endogenously produced GM-CSF. The IL-15-induced dendritic cells also expressed chemokines and stimulated strong allo-responses that were characteristic of mature dendritic cells. These data indicate that CD14(+) monocytes respond to IL-15 by undergoing morphological transformation and acquiring characteristic dendritic cell features that facilitate antigen-specific responses of T cells. Thus, the release of IL-15 by inflammatory stimuli may induce the conversion of monocytes to immuno-stimulatory dendritic cells to support primary immune responses against pathogens.

Differential expression of interleukin-15, a pro-inflammatory cytokine and T-cell growth factor, and its receptor in human prostate

BACKGROUND

Pro-inflammatory interleukin (IL)-15 plays a major role in host defense and chronic inflammation by stimulating T-lymphocyte recruitment and growth. Expression of IL-15 and IL-15 receptor (IL-15R) in human prostate was examined.

METHODS

Normal and benign hyperplastic (BPH) prostate specimens (n = 23) were analyzed for IL-15 and IL-15Ralpha-chain expression by immunohistochemistry and Real-Time-PCR/RT-PCR. Regulation of prostatic stromal cell (PSC) IL-15 mRNA and effect of IL-15 on prostatic cell growth were analysed in vitro.

RESULTS

In normal prostate, anti-IL-15 and anti-IL-15Ralpha-chain reactivity were restricted to smooth muscle and stromal cells. However, in BPH, in addition epithelial cells frequently exhibited discrete anti-IL-15R and often intense, membranous anti-IL-15 reactivity. IL-15/IL-15R mRNA were detected in all prostatic cells types. In BPH tissues, IL-15 mRNA content was variable (15-fold). IL-15 mRNA synthesis of PSC was significantly up-regulated by IFN-gamma. Furthermore IL-15 strongly stimulated the growth of BPH-T-lymphocytes and weakly that of carcinoma cell lines, but not of stromal cells.

CONCLUSIONS

Overexpression of IL-15 and IL-15Ralpha-chain in BPH and massive proliferation of BPH-T-lymphocytes induced by IL-15 suggest a role for IL-15 in prostatic inflammation. Since IFN-gamma, a T-lymphocyte product, stimulates prostatic IL-15 production; chronic inflammation might be triggered by this paracrine loop.

Functional monocyte-derived dendritic cells can be generated in chronic lymphocytic leukaemia

Chronic lymphocytic leukaemia (CLL) remains an incurable disease. Although modern available treatments are able to induce disease regression, relapse almost inexorably occurs. Therefore, novel therapeutic strategies aimed at reducing the disease relapse rate are very much needed. Among these, the induction of tumour-associated antigen-specific cytotoxic T lymphocytes (CTL), through either DNA vaccines or injection of idiotype pulsed dendritic cells (DCs), has been actively investigated with encouraging preliminary results in B-cell malignancies. As the CLL B lymphocyte characteristically expresses low amounts of surface immunoglobulin (Ig) and T cells from these patients have been reported to display impaired functional activity, there are concerns related to the possibility of generating specific cytotoxic antitumoral T cells in this disease. In addition, no information is presently available regarding the functional ability of CLL-derived DCs. In the present work, freshly purified monocytes from CLL patients and normal donors were induced to differentiate in granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin (IL)-4 serum-free medium and compared for their morphological, phenotypic and functional characteristics. Our results demonstrate that: (1) functional DCs can be generated from CLL patients with similar phenotype and function to those observed from normal donors; (2) in contrast to normal control subjects, monocyte-derived DCs from CLL patients spontaneously secrete endogenous IL-10; and (3) interferon (IFN)-gamma in combination with CD40L plays a major role in priming DCs from CLL patients for IL-12 and IL-15 production. Overall, these results indicate that it is possible to derive functionally competent DCs from circulating monocytes in CLL patients.

Ultraviolet light induced injury: immunological and inflammatory effects

This article reviews many of the complex events that occur after cutaneous ultraviolet (UV) exposure. The inflammatory changes of acute exposure of the skin include erythema (sunburn), the production of inflammatory mediators, alteration of vascular responses and an inflammatory cell infiltrate. Damage to proteins and DNA accumulates within skin cells and characteristic morphological changes occur in keratinocytes and other skin cells. When a cell becomes damaged irreparably by UV exposure, cell death follows via apoptotic mechanisms. Alterations in cutaneous and systemic immunity occur as a result of the UV-induced inflammation and damage, including changes in the production of cytokines by keratinocytes and other skin-associated cells, alteration of adhesion molecule expression and the loss of APC function within the skin. These changes lead to the generation of suppressor T cells, the induction of antigen-specific immunosuppression and a lowering of cell-mediated immunity. These events impair the immune system's capacity to reject highly antigenic skin cancers. This review gives an overview of the acute inflammatory and immunological events associated with cutaneous UV exposure, which are important to consider before dealing with the complex interactions that occur with chronic UV exposure, leading to photocarcinogenesis.

Lipopolysaccharide-stimulated or granulocyte-macrophage colony-stimulating factor-stimulated monocytes rapidly express biologically active IL-15 on their cell surface independent of new protein synthesis

Although IL-15 shares many of the biological activities of IL-2, IL-2 expression is primarily under transcriptional regulation, while the mechanisms involved in the regulation of IL-15 are complex and not completely understood. In the current study, we found that CD14(+) monocytes constitutively exhibit both IL-15 mRNA and protein. IL-15 protein was found stored intracellularly and stimulation of CD14(+) monocytes with either LPS or GM-CSF resulted in mobilization of IL-15 stores to the plasma membrane. This rapidly induced surface expression was the result of a translocation of preformed stores, confirming that posttranslational regulatory stages limit IL-15, because it was not accompanied by an increase in IL-15 mRNA and occurred independent of de novo protein synthesis. After fixation, activated monocytes, but not resting monocytes, were found to support T cell proliferation, and this effect was abrogated by the addition of an IL-15-neutralizing Ab. The presence of preformed IL-15 stores and the ability of stimulated monocytes to mobilize these stores to their surface in an active form is a novel mechanism of regulation for IL-15.

Interleukin-7 and interleukin-15 regulate the expression of the bcl-2 and c-myb genes in cutaneous T-cell lymphoma cells

Interleukin-7 (IL-7) and IL-15 have been recently identified as growth factors for cutaneous T-cell lymphoma (CTCL) cells, and they protect these cells from cell death. Using the CTCL cell line SeAx as a test system now shows that IL-7 and IL-15 are indeed necessary to maintain high levels of bcl-2. The up-regulation of bcl-2 was paralleled by increased DNA-binding activities of the transcription factors STAT2, STAT5, STAT6, and c-Myb to bcl-2 gene promoter-enhancer elements. Because STAT5 and c-Myb positively regulate bcl-2, IL-7 and IL-15 may mediate some of their effects on cell death survival gene expression through these 2 factors. Constitutive activities of the 3 STAT factors and c-Myb were found in the IL-7- and IL-15-independent CTCL cell lines HUT78 and MyLa 2059. The c-Myb protein was also present in CTCL cells of the skin lesions of all investigated patients. These results indicate that IL-7 and IL-15 may increase bcl-2 expression in CTCL cells by the activation of c-myb and STAT factors.