Skin irritants and contact sensitizers induce Langerhans cell migration and maturation at irritant concentration

Skin irritants and contact allergens reduce the number of Langerhans cells (LCs). It has been assumed that this reduction is due their migration to the draining lymph node (LN) for initiating immune sensitization in a host. Skin irritation, however, as opposed to contact allergy is not considered to be an immunological disease. Nevertheless, skin irritants are also known for their adjuvant-like effects on contact allergy, resulting in skin hypersensitivity reactions like toxic dermatitis. The human organotypic skin explant culture (hOSEC) model is used to study the characteristics of chemical-induced migration of CD1a(+) LCs out of the epidermis in relation to irritancy or toxicity. We analysed cells emigrating out of hOSEC for CD1a(+) LCs, CD83(+) mature dendritic cells (DCs) and CCR7(+) LN homing cells. After exposure to a toxic concentration of a non-immunogenic irritant, an increase of CD1a(+)CD83(+) LCs was found in the culture medium. A non-toxic concentration of an sensitizer induced an increase of CD1a(+) cells. About 50% of skin emigrating CD1a(+) LCs were CD83(-) (immature) but all were CCR7(+). Skin irritation by both non-allergenic and allergenic compounds induces LC migration and maturation. In contrast, only allergenic compounds induced LC migration with partial maturation at subtoxic concentration. This effectively demonstrates that irritation is physiologically needed stimuli for inducing LC maturation.     

Epidermal Langerhans cell apoptosis is induced in vivo by nonanoic acid but not by sodium lauryl sulphate

Exposure to irritants may cause chronic irritant contact dermatitis (ICD), characterized by irregular epidermal thickening and a predominantly dermal mononuclear cell infiltrate. The mechanisms involved, and why only certain individuals are affected, are not clearly understood. Different irritants may trigger different cellular and molecular interactions between resident skin cells and recruited inflammatory cells. In some individuals these interactions may become self-perpetuating resulting in persistent inflammation in the absence of continued exposure. This study examined Langerhans cell (LC) density in clinically normal skin of 46 patients with chronic ICD and 10 healthy individuals, and compared the action of the two irritants nonanoic acid (NA) and sodium lauryl sulphate (SLS) on the LCs and keratinocytes of clinically normal skin in patients with chronic ICD. There was a higher number of LCs/mm basement membrane in patients compared with controls, although there was no difference in the number of dendrites/LC nor in dendrite length. SLS induced keratinocyte proliferation after 48 h exposure, had no effect on LC number or distribution, and induced keratinocyte apoptosis after 24 and 48 h exposure. In contrast, NA decreased keratinocyte proliferation after 24 h exposure but this returned to basal levels after 48 h, and induced epidermal cell apoptosis after only 6 h exposure. NA dramatically decreased LC number after 24 and 48 h exposure, which was accompanied by basal redistribution and decreased dendrite length. Most significantly, NA induced apoptosis in over half of the LCs present after 24 and 48 h exposure.     

Induction of cytokine (interleukin-1alpha and tumor necrosis factor-alpha) and chemokine (CCL20, CCL27, and CXCL8) alarm signals after allergen and irritant exposure

The immune system is called into action by alarm signals generated from injured tissues. We examined the nature of these alarm signals after exposure of skin residential cells to contact allergens (nickel sulfate and potassium dichromate) and a contact irritant [sodium dodecyl sulfate (SDS)]. Nickel sulfate, potassium dichromate, and SDS were applied topically to the stratum corneum of human skin equivalents. A similar concentration-dependent increase in chemokine (CCL20, CCL27, and CXCL8) secretion was observed for all three chemicals. Exposure to nickel sulfate and SDS was investigated in more detail: similar to chemokine secretion, no difference was observed in the time- and concentration-dependent increase in pro-inflammatory cytokine [interleukin-1alpha (IL-1alpha) and tumor necrosis factor-alpha (TNF-alpha)] secretion. Maximal increase in IL-1alpha secretion occurred within 2 h after exposure to both nickel sulfate and SDS and prior to increased chemokine secretion. TNF-alpha secretion was detectable 8 h after chemical exposure. After allergen or irritant exposure, increased CCL20 and CXCL8, but not CCL27, secretion was inhibited by neutralizing human antibodies to either IL-1alpha or TNF-alpha. Our data show that alarm signals consist of primary and secondary signals. IL-1alpha and TNF-alpha are released as primary alarm signals, which trigger the release of secondary chemokine (CCL20 and CXCL8) alarm signals. However, some chemokines, for example, CCL27 can be secreted in an IL-1alpha and TNF-alpha independent manner. Our data suggest that skin residential cells respond to both allergen and irritant exposure by releasing mediators that initiate infiltration of immune responsive cells into the skin.     

Measurement of cytokine expression and Langerhans cell migration in human skin following suction blister formation

Contact allergen-induced migration of epidermal Langerhans cells (LCs) to draining lymph nodes is dependent upon receipt by LCs of at least two cytokine signals provided by tumor necrosis factor-alpha (TNF-alpha) and interleukin (IL)-1beta. It has been reported previously that intradermal injection of healthy human volunteers with homologous TNF-alpha or IL-1beta each induces a significant reduction in LC frequency, as measured in epidermal sheets prepared from 6-mm punch biopsies. In the current experiments, we have compared the frequency of LCs in punch biopsies with those obtained concurrently in epidermal sheets from the roofs of suction blisters isolated from the sun-protected buttock skin of healthy adult volunteers. There was a significant, approximately 30%, reduction in CD1a(+) LC numbers in suction blister roofs compared with punch biopsies. Injection of homologous recombinant IL-1beta, a stimulus that provokes measurable epidermal LC mobilization in punch biopsy sites, failed to provoke further LC migration in suction blister sites. These data suggest that the mechanical trauma to the skin caused by the creation of suction blisters provokes the degree of cutaneous inflammation necessary for LC mobilization. The responsive cells (only a proportion of resident LCs, approximately 30%) have already migrated, thus addition of an exogenous cytokine signal (IL-1beta) is without further effect. It is not possible therefore to measure the regulation of LC mobilization by exogenous cytokines in suction blister roofs. However, this technique provides an opportunity to profile induced changes in the cutaneous cytokine environment, with cytokine expression measured by a multiple cytokine array system. Using this technique, intradermal injection of IL-1beta was found to cause a marked upregulation of proinflammatory cytokines including TNF-alpha, IL-6, IL-8, monocyte chemotactic protein-1 (MCP-1) and the anti-inflammatory cytokine IL-10 in fluid from suction blisters raised at the site of injection. In conclusion, the suction blister technique appears to be a powerful tool for measurement of induced changes in cutaneous cytokines.     

IL-10-producing Langerhans cells and regulatory T cells are responsible for depressed contact hypersensitivity in grafted skin

Although skin grafting is a common surgical technique, the immunological state of grafted skin remains unelucidated. An experimental model has shown that the development of murine contact hypersensitivity (CHS) is depressed when mice are sensitized with a hapten through full-thickness grafted skin. We explored the immunological mechanisms underlying this hyposensitization, focusing on the fate of Langerhans cells (LCs). When FITC was applied to grafted skin, FITC-bearing LCs were capable of migrating to the draining lymph nodes. Epidermal cell suspensions isolated from the grafted skin produced a high amount of IL-10 as assessed by real-time PCR. Adoptive transfer of immune lymph node cells from the sensitized mice suppressed the CHS response of recipients in an antigen-specific manner. CD4(+)CD25(+) but not CD4(+)CD25(-) T cells purified from lymph node cells were responsible for this suppression. Finally, we detected high expression of receptor activators of nuclear factor kappa-B ligand (RANKL) in the grafted skin, and found that recombinant RANKL stimulated LCs to produce IL-10. These findings suggest that the hyposensitization of CHS through the grafted skin is not attributable merely to the reduction of LC number but that IL-10-producing LCs exert a downmodulatory effect by inducing regulatory T cells.     

IL-13-stimulated human keratinocytes preferentially attract CD4+CCR4+ T cells: possible role in atopic dermatitis

Skin inflammation in atopic dermatitis (AD) is characterized by the predominant infiltration of T-helper (Th)2-cells in lesional skin. However, the mechanism of recruitment of these cells in lesional skin of AD is not yet fully elucidated. In this study, we investigated the role of IL-13-stimulated human primary keratinocytes (HPKs) in the recruitment of lymphocytes and further delineated the mechanism of enrichment of these cells. In the migration assays, we observed preferential enrichment of CD4(+)CCR4(+) T cells towards IL-13-stimulated HPKs. Interestingly, CD4(+)CCR4(+) T cells from AD showed a higher chemotactic response than those from healthy individuals. We observed a significant increase in the expression of CCL22 in IL-13-stimulated HPKs as compared to unstimulated cells. Blocking of CCL22 in IL-13-stimulated HPKs by a neutralizing antibody resulted in 70-90% inhibition in migration of CD4(+)CCR4(+) T cells. Moreover, IL-13 upregulated IFN-gamma-induced chemokines, CCL2 and CCL5, in HPKs. Taken together, our data suggest that IL-13-stimulated HPKs participate in a positive feedback loop by preferentially enriching Th2-cells in lesional skin of acute AD patients. However, in chronic phase, IL-13 may act in synergy with IFN-gamma resulting in lymphocytes recruitment of a mixed phenotype at the site of inflammation, thus contributing to the chronification of eczema.     

In vivo cytokine profiles in allergic and irritant contact dermatitis

Local cytokine profiles in skin biopsies from allergic and irritant patch test reactions were determined by in vivo immunohistochemistry to differentiate between these 2 clinically identical afflictions especially at the time of final reading in diagnostic patch testing. Biopsies were taken from established allergic persons after specific allergic patch test.-, to epoxy resin (1%) and formaldehyde (1%) and from non-allergic individuals with irritant patch tests to sodium lauryl sulfate (10%) and formaldehyde (8%). At 72 h after application of the agents, significantly enhanced frequencies of dermal infiltrating cells, producing IL-1α, TNF-α. IL-2. and IFN-γ per 100 infiltrating cells in the dermis. were observed in allergic as well us irritant patch test reactions, as compared to normal skin. Significantly higher frequencies of IL- Iα-producing cells were observed in biopsies from epoxy resin (1%) allergen-affected and sodium lauryl sulfate (10%) irritant-affected skin as compared to formaldehyde (1%) allergen-affected skin. In addition, significantly higher frequencies of TNF -α reproducing cells were observed in epoxy resin allergen-affected skin us compared to Formaldehyde (1%) allergen-affected and formaldehyde (8%) irritant affected skin. The allergic and irritant patch test reactions showed similar levels of expression of the Thl cytokines IL-2 and IFN-γ in the dermis. confirmed by probe based detection of IL-2 mRNA and IFN-γ- mRNA, In conclusion, the described similarity shows that allergens and irritants can induce the same profile of IL-la. TNF-α. IL-2. and IFN-γ production, resulting in the near impossibility of discriminating between allergic and irritant contact dermal is at the lime of patch test reading.     

Subtoxic concentrations of allergenic haptens induce LC migration and maturation in a human organotypic skin explant culture model: a novel method for identifying potential contact allergens

The accelerated migration of Langerhans cells (LCs) out of the epidermis and up-regulation of maturation markers, upon treatment with subtoxic concentrations of chemicals, were used as the criteria to determine the potential of allergenic chemicals capable of inducing a hapten-specific delayed-type hypersensitivity reaction. Here we report the findings of a study in which seven chemicals, coded and tested in a blind fashion, were classified as contact allergens or non-allergens using the human organotypic skin explant culture (hOSEC) model. All chemicals that were identified as a contact sensitizer on decoding induced a definite decrease in the number of CD1a and HLA-DR-positive epidermal LCs in the epidermis of the skin explants, as determined by both semiquantitative immunohistochemistry and quantitative flow cytometric analysis. A significant increase in the number of CD83(+) cells was accompanied by up-regulation of activation molecules in the epidermis of hOSEC exposed specifically to contact allergens. In contrast, there were only minor alterations in epidermal LC numbers, expression of CD83 and other activation markers by LCs when the biopsies were treated with non-toxic concentrations of non-allergenic irritants and vehicles. The data suggest that an increased epidermal LC migration and maturation accompanied by increased expression of activation markers could be used as end-point determinants to screen allergens in a non-animal alternative hOSEC model.     

Immunophenotypic analysis of normal human dendritic cells isolated from epidermis and dermis

Background The skin immune system comprises two types of dendritic cells, i.e. CD1a-positive Langerhans cells in the epidermis and CD36-positive dendritic macrophages in the dermis. Dendritic cells can migrate from skin explants into a culture medium.
Methods We have examined the morphology and immunophenotype of the dendritic cells migrating from epidermal and dermal sheets in vitro. The epidermis and dermis of keratomes of normal human skin were separated with dispase and cultured for 72 h. At this time, the non-adherent cells in the medium were removed, enriched on a metrizamide or Lymphoprep gradient, counted, prepared by cytospin, and labeled for CD1a, CD36, and HLADr.
Results Cells migrating from the epidermis and dermis show many thin projections or a few veils from the cell surface. Approximately four times more cells migrate from epidermal than dermal sheets from the same keratome.
Conclusions Using methods to separate the epidermis from the dermis, both CD1a-positive Langerhans cells and CD36-positive dendritic macrophages can be obtained from both tissues, although in different numbers.     

An immunohistochemical analysis of cytokine expression in allergic and irritant contact dermatitis

The purpose of this study was to investigate whether the specific and non-specific inflammatory responses to allergens and irritants give rise to immuno-histochemical detectable differences in the cytokine profile in the skin. Skin biopsies taken at 0, 6, 24 and 72 h from contact allergic reactions to nickel and from irritant reactions to sodium lauryl sulphate were analysed. The main finding was that the dermal cells expressed similar patterns of cytokines (IL-1alpha, IL-1beta, IL-2, IL-4, IL-6 and IL-10) in both types of contact reaction at 72 h. However, two differences were observed. Staining for the IL-1 receptor antagonist was more prominent in the dermis at the late stages of the allergic reaction compared with the late stage of the irritant reaction. The other difference was an increased interferon-gamma staining of infiltrating mononuclear inflammatory cells in the dermis in the sodium lauryl sulphate group compared with the nickel group. A more rapid general onset of cytokine production was found in the sodium lauryl sulphate group than in the nickel group. The main conclusion of this study was that after 6 h the cytokine patterns did not differ between the specific and the non-specific inflammatory responses in the skin.     

Type I interferons inhibit maturation and activation of mouse Langerhans cells

Type I interferons (IFN) have an essential role in antiviral defense, and they are produced upon viral infection in a variety of cells. IFN-alpha/beta treatment of immature dendritic cells (DC) is known to induce their phenotypic and functional maturation, but it remains unclear whether stimulation by this cytokine family influences the functions and maturation of Langerhans cells (LC). We used highly enriched (>95%) LC directly isolated from BALB/c mouse skin and addressed this issue, comparing LC with splenic CD11c(+) DC. Type I IFN-treated LC exhibited impaired ability to produce IL-12 and inflammatory cytokines, IL-6 and TNF-alpha, whereas IL-10 production was not augmented. In splenic DC, the production of inflammatory cytokines was rather enhanced by type I IFN treatment. With regard to chemokines, in both LC and splenic DC, type I IFN upregulated the production of inflammatory chemokines, such as CXCL10, CXCL11, CCL3, CCL4, and CCL5. Strikingly, IFN-beta treatment reduced the expression of CD40, CD54, CD80, and CD86 on LC, whereas IFN-beta-treated splenic DC showed enhanced expression of these molecules. Furthermore, IFN-beta-treated LC had impaired costimulatory activity for anti-CD3-induced proliferation of T cells. Finally, treatment with IFN-alpha/beta reduced the migratory capacity of LC to CCL21. These results indicate that type I IFN inhibit maturation and activation of LC in a direct manner. Our observations may provide a novel explanation for the reported inability of LC to act as potent antigen-presenting cells in cutaneous and mucosal viral infection.     

Roles for IL-1 and TNFalpha in dynamic behavioral responses of Langerhans cells to topical hapten application

BACKGROUND: To understand the behavioral biology of Langerhans cells (LCs), we recently recorded time-lapse images of LCs in the knock-in mice expressing the I-Abeta chain tagged with the enhanced green fluorescence protein (EGFP). EGFP(+) LCs showed relatively limited motility in the steady state, whereas topical application of dinitrofluorobenzene (DNFB) markedly augmented a unique movement of dendrites characterized by rhythmic extension and retraction, termed dSEARCH, and triggered amoeba-like lateral migration of cell bodies. OBJECTIVE: To define underlying mechanisms by which hapten treatment alters LC behaviors. METHODS: The I-Abeta-EGFP mice received subcutaneous (s.c.) injection of recombinant IL-1alpha or TNFalpha (50 ng/animal) and dynamic behaviors of EGFP(+) LCs were recorded by time-lapse confocal microscopy at several time points to measure their dSEARCH activities and lateral migration. In a different set of experiments, IL-1 receptor antagonist (IL-1Ra) or soluble TNF receptor-2 (sTNFR2) (0.5 microg/animal) was s.c. injected into the ear skin 30 min before topical application of DNFB, and LC behaviors analyzed 30 h later. RESULTS: Local injection of IL-1alpha or TNFalpha induced significant, albeit modest, augmentation of both dSEARCH and lateral migration. Co-injection of TNFalpha and IL-1alpha further exacerbated motile activities in a synergistic manner by similar magnitudes observed after DNFB application. Conversely, DNFB-induced behavioral changes were inhibited completely by local injection of IL-1Ra or sTNFR2. CONCLUSION: IL-1 and TNFalpha serve as equally important mediators of hapten-induced alteration of LC behaviors. Motile activities of epidermal LCs are reprogrammed by selected cytokines known to be produced by keratinocytes under pathological conditions.     

Prominent Langerhans' cell migration in the arthropod bite reactions simulating Langerhans' cell histiocytosis

BACKGROUND: Epidermal Langerhans' cells (LCs) play pivotal roles in cutaneous immune responses. An encounter with antigens or other stimuli causes the mobilization and migration of LCs. Therefore, some dermatoses, which originated from antigenic stimuli or trauma, can show LC migration. Recently, we experienced several cases of anthropod bites that showed marked inflammatory infiltrates with eosinophils and CD1a-positive LCs. It was difficult to differentiate these cases from Langerhans' cell histiocytosis (LCH). METHODS: The degree and pattern of LC infiltration in the skin of arthropod bite reaction was evaluated. The characteristics of CD1a immunohistochemical expression in the arthropod bite reactions were compared with those of LCH. RESULTS: A few arthropod bite cases (approximately 36%) showed extensive CD1a-positive LCs in the dermis, especially in the perivascular area. In addition, the CD1a expression patterns of LCs in the arthropod bite reactions were dendritic, whereas that of tumor cells in LCH were distinctly membranous and cytoplasmic. CONCLUSION: Some arthropod bite reactions can show marked CD1a-positive LCs in the dermis, especially in the perivascular area. The dendritic CD1a immunohistochemical staining pattern in arthropod bite reactions is useful in helping to differentiate from LCH.     

Augmentation of skin response by exposure to a combination of allergens and irritants - a review

Clinical experimental studies on contact dermatitis (CD) often evaluate the effect of one allergen or one irritant at a time. In real life, the skin is often exposed to more allergens, more irritants or allergens and irritants in combination. This combined exposure may potentially influence irritant effects as well as allergenicity of the substances. Mechanisms for a changed response can be immunological effects or enhanced penetration. Knowledge about the influence on skin reaction of combined exposures may influence skin reactivity and is important for prevention of CD. For allergens, threshold values may be influenced by the presence of other allergens or irritants, and prevention of CD by regulation of threshold values may not be sufficient if this is not taken into account.     

Phenotypic and functional outcome of human monocytes or monocyte-derived dendritic cells in a dermal equivalent.

The dermis harbors a true dendritic cell population that could elicit primary allogeneic T cell responses in vitro and contact hypersensitivity reactions in vivo. The origin of dermal dendritic cells remains poorly understood, however. In this study, we analyzed the fate of monocytes or monocyte-derived dendritic cells in a dermal equivalent. Freshly isolated monocytes or monocytes cultured for 6 d with either GM-CSF/IL-4 or GM-CSF/IL-4/TGF-beta 1 (TGF-DC) were seeded in a collagen solution with normal human fibroblasts. The lattices were cultured for 7--14 d in the presence, or absence, of the exogenous cytokines, before phenotypic and functional studies were performed. Supply of exogenous cytokines allows the appearance of typical CD1a(+)/CD14(-)/CD68(low) dendritic cells with significant allostimulatory property, regardless of the cell type incorporated into the lattices. In cytokine-free conditions, monocytes and GM-CSF/IL-4-derived dendritic cells give rise to a CD1a(-)/CD14(+)/CD68(high) monocyte/macrophage population with no allostimulatory property. When incorporated into the lattices in the absence of exogenous cytokines the TGF-DC express few CD68 and FXIIIa. Interestingly, these cells do not all convert into the CD14(+)/CD1a(-) population. Indeed, a small HLA-DR(+)/CD1a(+)/CD14(-) subset was consistently found, which represents about one-third of the HLA-DR(+) cells. Moreover, TGF-DC recovered from the lattices after culture without cytokines do display a significant allostimulatory function. Thus, in the absence of exogenous cytokines, only Langerhans-cell-like dendritic cells can retain the typical dendritic cell features when inserted in a dermal environment. Taken together, these results may provide evidence supporting an epidermal origin of dermal dendritic cells.     

IL6Rα function in myeloid cells modulates the inflammatory response during irritant contact dermatitis

Irritant contact dermatitis (ICD) is characterized by epidermal hyperplasia, infiltration of leucocytes into lesional skin and inflammatory cytokine release. The cellular infiltrate during ICD comprises primarily cells of the myeloid lineage. Our group has previously shown that the cytokine IL‐6 confers a protective effect to lesional skin during ICD. How IL‐6Rα function in myeloid cells is involved in the inflammatory response during ICD is, however, unknown. In the present study, utilizing a chemical model of ICD, it is shown that mice with a myeloid‐specific knockout of the IL‐6Rα (IL‐6Rα^Δmyeloid) display an exaggerated inflammatory response to benzalkonium chloride (BKC) and Jet propellant‐8 (JP8) fuel, two well‐characterized irritants relative to littermate control. Results from immunohistochemical and flow cytometric analyses revealed that IL‐6Rα^Δmyeloid mouse skin displayed increased epidermal hyperplasia and inflammatory monocyte influx into lesional skin but lower numbers of resident macrophages relative to littermate controls after irritant exposure. Multiplex immunoassay revealed significantly higher levels of pro‐inflammatory cytokines IL‐1α and TNF‐α, but reduced expression of chemokine proteins including CCL2‐5, CCL7, CCL11, CXCL1 and CXCL10 in IL‐6Rα^Δmyeloid mouse skin relative to littermate control following irritant exposure. These results highlight a previously unknown role of IL‐6Rα function in myeloid cells in modulating the inflammatory response and myeloid population dynamics during ICD.     

Skin application of the nonsteroidal anti-inflammatory drug ketoprofen downmodulates the antigen-presenting ability of Langerhans cells in mice

Background  Ketoprofen (KP) is widely used as a topical nonsteroidal anti-inflammatory drug that inhibits prostaglandin (PG) biosynthesis. As PGE₂ upregulates the antigen-presenting activity of Langerhans cells (LCs), i.e. migration to lymph nodes and expression of immunocompetent molecules, modulation of LC functions resulting from topical application of KP is an issue to be clarified.
Objectives  To investigate the in vivo effect of KP application to the skin and the in vitro effect of KP addition to the culture on the antigen-presenting ability of murine LCs.
Methods  Ears of BALB/c mice were painted with picryl chloride (PCl) hapten, KP or both. An immunofluorescence study of epidermal sheets and a flow cytometric analysis of epidermal cell suspensions from the treated ears were performed.
Results  PCl altered the morphology of LCs and reduced their number, and simultaneous application of 10% KP maintained LC morphology and number. KP at 5% or 10% clearly decreased the PCl-augmented expression of major histocompatibility complex class II and CD86 on LCs. In cultivation of freshly isolated epidermal cells, 5 mmol L⁻¹ KP inhibited the culture-promoted expression of these molecules on LCs, whereas 100 μmol L⁻¹ indomethacin was not inhibitory. The further addition of PGE₂ to the KP-containing epidermal cell culture did not restore the expression of these molecules. Moreover, topical application of 10% KP to the sensitizing sites suppressed the development of contact hypersensitivity to PCl.
Conclusions  KP may have the potential to inhibit the antigen-presenting ability of LCs, in a PGE₂-independent manner.     

Langerhans cells from human cutaneous squamous cell carcinoma induce strong type 1 immunity

Langerhans cells (LCs) are dendritic cells (DCs) localized to the epidermis. They should be the first antigen-presenting cells to encounter squamous cell carcinoma (SCC). The aim of this study was to investigate the ability of LCs isolated from human SCC to induce T-cell proliferation and polarization. We investigated the ability of LCs from SCC and peritumoral skin to induce T-cell proliferation and polarization. We also studied the effect of SCC supernatant on the ability of LCs from normal skin, in vitro-generated LCs, and DCs to activate and polarize T cells. LCs from SCC were stronger inducers of allogeneic CD4(+) and CD8(+) T-cell proliferation and IFN-γ production than LCs from peritumoral skin. We found that tumor supernatants (TSNs) were rich in immunosuppressive cytokines; despite this, allogeneic CD4(+) and CD8(+) T-cell proliferation and IFN-γ induction by LCs were augmented by TSN. Moreover, TSN facilitated IFN-γ induction by in vitro-generated LCs, but suppressed the ability of in vitro-generated DCs to expand allogeneic CD4(+) and CD8(+) T cells. We have demonstrated that LCs from SCC can induce type 1 immunity. TSN induces IFN-γ induction by in vitro-generated LCs. This contrasts greatly with prior studies showing that DCs from SCC cannot stimulate T cells. These data indicate that LCs may be superior to DCs for SCC immunotherapy and may provide a new rationale for harnessing LCs for the treatment of cancer patients.     

No impairment of monocyte-derived Langerhans cell phenotype or function in early-onset psoriasis

Background. Migration of epidermal Langerhans cells (LCs) in response to the cytokines interleukin (IL)‐1β and tumour necrosis factor (TNF)‐α is impaired in uninvolved skin of patients with early‐onset psoriasis. Aim. To investigate whether this impairment is a reflection of a systemic defect in dendritic cells (DCs), using an established model of monocyte‐derived LC‐like cells (mLCs). Methods. CD14+ monocytes isolated from both patients with psoriasis and healthy control volunteers were cultured in a cytokine cocktail for 5 days to promote their differentiation into mLCs, then stimulated for 24 h with TNF‐α, IL‐1β (both 100 ng/mL) or medium alone. Cellular surface protein expression was quantified by flow cytometry, and the ability of cells to migrate to media supplemented with C‐C motif ligand (CCL)19 was assessed using a Transwell migration assay. The cytokine and chemokine content of supernatants was analysed by cytokine array. Results. CD14+ cells acquired an LC‐like phenotype with high expression of CD1a and major histocompatibility complex (MHC) class II. There were no differences in the expression of activation markers or in the secretion of cytokines by mLCs isolated from patients with psoriasis and those isolated from healthy controls. Moreover, mLCs isolated from both groups displayed comparable ability to migrate in vitro. Conclusions. These data suggest that the failure of LCs to migrate in response to stimulation in patients with psoriasis is not attributable to a systemic defect in DC function, but is rather a reflection of local changes in the epidermal microenvironment.