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Summary: Langerhans cells (LC) are constantly exposed to external antigens and pathogens, and they are the cutaneous counterpart of dendritic cells (DC). DC not only act as professional antigen presenting cells to induce antigen-specific T cells for adaptive immune responses, but they also initiate a cascade of innate immune responses by sensing these danger signals. However, recent studies challenge the classical paradigm to position LC in the center of cutaneous immunity. Although LC express toll-like receptors (TLRs) that recognize bacterial and viral products, exposure to pathogen-associated TLR ligands triggers neither sufficient LC maturation nor good production of cytokines and chemokines. LC also lack the ability to produce IFN-γ by any stimuli, and together with the characteristics of LC that are prone to produce Th2-type chemokines and to produce much less IL-12 in the presence of keratinocyte-derived GM-CSF, LC primarily may not have the character to induce Th1- and Tc1-type immune responses necessary for protective cellular immunity. Moreover, LC maturation is inhibited, rather than enhanced, by type I IFNs that are abundantly produced in viral infections in the skin microenvironment. Finally, recent data suggest that LC may not directly present viral antigens to T cells for their activation in mouse models of cutaneous viral infection. The alternative player in protective immune responses may be surrounding keratinocytes, which may modulate LC functions indirectly. Dermal DC may also participate in this scheme. Further studies are required to clarify the role of LC in their interplay with keratinocytes and other DC subsets, and to draw the entire picture of the cutaneous immune system against pathogens. [Copyright &y& Elsevier]

Background: Treatments of port-wine stains with conventional pulsed dye laser yield inconsistent results. Objective: We evaluated the efficacy and safety of the longer pulse duration 595-nm dye laser. Methods: Sixty-six adult Japanese patients were enrolled in this prospective study. The laser treatment with a cooling device was repeated 4 times at 8-week intervals with a consistent setting of 10-ms pulse duration and an energy fluence of 12 J/cm2, using 7-mm spot size. Results: Improvement of port-wine stains was observed after multiple treatments, and 67% of the patients achieved either good or excellent response after the fourth treatment. Transient purpura, edema, or both were noted immediately after each treatment (76%-79% and 58%-67%, respectively). Hyperpigmentation (8%-17%) and hypopigmentation (6%-14%) were also mild and their occurrence did not increase by repeating treatments. Limitations: Eighty five percent of the patients were classified as having Fitzpatrick skin type IV. Conclusion: Our study indicated that the 595-nm dye laser with 10-ms pulse duration may be effective and well tolerated in the treatment of port-wine stains in adult Asians. [Copyright &y& Elsevier]

Type I interferons (IFN) have an essential role in antiviral defense, and they are produced upon viral infection in a variety of cells. IFN-α/β 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-α, 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-β treatment reduced the expression of CD40, CD54, CD80, and CD86 on LC, whereas IFN-β-treated splenic DC showed enhanced expression of these molecules. Furthermore, IFN-β-treated LC had impaired costimulatory activity for anti-CD3-induced proliferation of T cells. Finally, treatment with IFN-α/β 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. [ABSTRACT FROM AUTHOR]

Some chemokines specifically attract T helper 1 (Th1) cells, whereas others attract T helper 2 (Th2) cells. In this study, we investigated the capacity of Langerhans cells (LC) to produce Th1- and Th2-type chemokines in comparison with that of splenic CD11c+ dendritic cells (DC). We prepared highly purified (>95%) LC from BALB/c mouse skin using the panning method. With regard to Th1-type chemokines, exogenous stimulus, such as interferon-γ (IFN-γ), lipopolysaccharide, or polyinosinic–polycytidylic acid, was mandatory for the production of substantial amounts of CXCL10, CXCL9, and CXCL11 both in LC and splenic DC. LC, as a whole, exhibited low ability to produce Th1-type chemokines in comparison with splenic DC. As for Th2-type chemokines, LC, but not splenic DC, produced high levels of CCL22 and CCL17 constitutively during culture even without exogenous stimuli. The production of Th2-type chemokines was regulated in a complicated manner. In particular, interleukin-4 upregulated, and IFN-γ downregulated both CCL22 and CCL17 production by LC. Of note, LC produced much more amounts of Th2-type chemokines than splenic DC under any conditions tested. Finally, Th1- and Th2-type chemokines produced by LC were shown to be functional using chemokine receptor-transfected-2B4 T cells. The high production of CC chemokine receptor 4 ligands by LC in the absence of IFN-γ may be an important character discriminating LC from other DC. [ABSTRACT FROM AUTHOR]

The association of specific HLA-C nucleotide sequences with psoriasis vulgaris was investigated in 75 Japanese patients by the polymerase chain reaction method, followed by slot-blot hybridization using two specific oligonucleotide probes. The synthesized nucleotide primers were C180P, 5'-GACCGGGAGACACAGAAGTACAAG-3' (coding for amino acid residues 61 to 68 of the α1 domain of the HLA-C molecule) and C243PR, 5'-GCTCTGGTTGTAGTAGCCGCG-3' (residues 82 to 88), respectively. The amplified sequence detected with the probe C208A (5'-AGGCACAGGCTGACCGA-3'), including the coding region for alanine at position 73, was significantly increased in frequency in the patients compared with the healthy individuals (81% versus 48%, relative risk = 4.7, χ2 = 15.3, p < 0.0001). This specific nucleotide sequence is common to Cw6 and Cw7, but some other HLA-C alleles including Cw4 and C blank (Cx52) also proved to have this sequence. It is suggested that alanine at position 73 of HLA-C molecules can be a good marker for psoriasis vulgaris and that this residue may play an important role in determining susceptibility to this disease. [ABSTRACT FROM AUTHOR]

Presents a letter to the editor about inflammatory chemokines.

Deals with a study which examined the direct effects of several cytokines on Langerhans cell interferon-γ production, without interference of keratinocytes and keratinocyte-derived cytokines, in mouse skin. Use of reverse transcription polymerase chain reaction; Langerhans cell isolation; Role of T cells in protecting the skin.

Early inflammatory changes in psoriatic plaques were investigated immunohistochemically by studying the normal-appearing skin adjacent to the plaques (perilesional skin), lesional skin, and distant uninvolved skin from psoriasis patients. Perilesional epidermis contained numerous CD1a-positive Langerhans cells, some of which expressed HLA-DR, CD83, CD80, and CD86, at the same time expressing Langerin. There were also numerous CD83-positive, CD11c-positive, Langerin-negative dendritic cells (DCs) in the epidermal–dermal junction of perilesional skin. CD3-positive T lymphocytes were sparse in the perilesional skin. Perilesional epidermis expressed keratin K6 and K16, inflammatory keratins, and C/EBPβ, a transcription factor related to inflammatory cytokines. Our results demonstrated the abundant distribution of activated DCs in the perilesional skin of psoriatic plaques, where early inflammatory changes occur in the epidermal keratinocytes, which suggests their involvement in the provocation of epidermal inflammation in the perilesional epidermis and further pathogenic roles in the formation of psoriatic plaques.Journal of Investigative Dermatology (2007) 127, 1915–1922; doi:10.1038/sj.jid.5700799; published online 19 April 2007 [ABSTRACT FROM AUTHOR]

Toll-like receptors are key elements in pathogen recognition by the host immune system. Although the expression pattern and functions of Toll-like receptors have been studied in a variety of cytokine-induced dendritic cells, it remains unknown whether Toll-like receptor stimulation influences maturation and cytokine production of authentic Langerhans cells. We purified murine epidermal Langerhans cells along with splenic dendritic cell using a panning method. Langerhans cells expressed Toll-like receptor 2, 4, and 9 but not 7, the pattern of which suggests Langerhans cells are the closest to one of the murine dendritic cell lineage, CD11c+11b+8α–4–. Then we stimulated Toll-like receptor 2, 4, and 9 with the corresponding ligand, Staphylococcus aureus Cowan 1, lipopolysaccharide, and CpG, and found that all of these stimuli upregulated expression of B7-1 and B7-2 in splenic dendritic cells but not in Langerhans cells. As in human Langerhans cells, stimulation of murine Langerhans cells with Staphylococcus aureus Cowan 1, lipopolysaccharide, and CpG overall resulted in T helper 1-polarizing cytokine production (namely, induction of IL-12p40 and inhibition of TARC (thymus and activation-regulated chemokine)/CCL17). Exceptionally, lipopolysaccharide exhibited no effect on IL-12p40 production by Langerhans cells and inhibited IL-12p40 production by splenic dendritic cells. These results may represent the functional heterogeneity between Langerhans cells and splenic dendritic cells, and are important for better understanding of innate immunity to bacterial infections differentially regulated in the skin and spleen. MeSH terms: Toll-like receptors, Langerhans cells, dendritic cells. [ABSTRACT FROM AUTHOR]

Background: Macrophage-derived chemokine (MDC) is a Th2 type chemokine and its receptor CC chemokine receptor 4 (CCR4) is preferentially expressed on Th2 cells. Recent reports demonstrated that MDC is expressed not only by macrophages, dendritic cells and lymphocytes, but also by cultured human keratinocytes (KCs). However, the regulation of MDC production in KCs by various cytokines has not been well documented. Objective: In this study, we investigated how Th1/Th2 cytokines regulate MDC production in a human KC cell line, HaCaT cells. Methods: HaCaT cells were cultured with or without various cytokines for 24 h and RT-PCR was performed using these cells to evaluate MDC mRNA levels. ELISA was carried out using supernatant of HaCaT cells to calculate secreted MDC protein levels. Results: MDC mRNA was weakly expressed in HaCaT cells, and upon stimulation with TNF-α or IFN-γ, MDC expression was strongly upregulated. The supernatant MDC levels when stimulated with TNF-α or IFN-γ were significantly higher than those without stimulation, and were synergistically increased when stimulated with a combination of TNF-α and IFN-γ. Both interleukin-4 (IL-4) and IL-13 inhibited TNF-α and IFN-γ enhanced MDC production in HaCaT cells in a dose-dependent manner. Conclusion: Th2-type cytokines IL-4 and IL-13 downregulate the production of MDC, a Th2 type chemokine, by KCs. This may partially contribute to maintaining Th1/Th2 balance in inflammatory skin diseases like atopic dermatitis. [Copyright &y& Elsevier]

Interleukin-12 (IL-12) is believed to play an important role in inducing Th1-type cytokine profiles. Atopic dermatitis (AD) and psoriasis vulgaris (PsV) are considered to be Th2 and Th1 type disease, respectively. The IL-12 p40 subunit gene (IL12B) is located at chromosome 5q31-33 and linkage findings of AD on 5q31 were reported. Recently single nucleotide polymorphism (SNP) (1188A/C) of IL12B has been reported. In function, it has been reported that this SNP is associated with IL12B mRNA expression levels. To learn whether this SNP is associated with susceptibility to AD or PsV, we investigated the genotype and allele frequencies of the SNP in AD patients, in PsV patients and in controls, examining 164 AD patients, 143 PsV patients and 100 healthy individuals in Japanese population. Genotyping was performed using the polymerase chain reaction-restriction fragment length polymorphism method. The A allele was decreased in AD patients (40.9%, p=0.031) and increased in PsV patients (60.1%, p=0.035) compared with controls (50.5%). This suggests that IL12B SNP is associated with susceptibility to AD and PsV, presumably by affecting the Th1/Th2 balance. [Copyright &y& Elsevier]

We examined polymorphisms of vitamin D receptor (VDR) gene in Japanese patients with psoriasis vulgaris (PsV). We also studied the association between VDR gene polymorphisms and the response to vitamin D (VD) topical treatment in psoriatic patients. FokI, BsmI, ApaI and TaqI genotypes were determined by restriction fragment patterns in patients (n=115) and controls (n=69). In addition, 54 psoriatic patients were divided into two groups in terms of their response to VD (tacalcitol) topical treatment: non-responsive (n=30) and responsive (n=24) patients. The frequencies of B allele and t allele were lower in patients than in controls (9 vs. 19%: p<0.01, 7 vs. 14%: p<0.05, respectively). In regard to response to VD treatment, F allele was lower in non-responsive patients than in controls (47 vs. 64%, p<0.05). We show that polymorphisms of VDR gene are associated with Japanese patients with PsV. Allelic variance in the VDR gene or other genes in linkage disequilibrium with this gene might predispose to the development of PsV. [Copyright &y& Elsevier]

CD23 is a low-affinity receptor for immunoglobulin E and expressed on various hemopoietic cells. Although human epidermal cultured Langerhans cells express CD23, the study to identify CD23 on murine Langerhans cells has so far failed. In this study, using highly enriched (> 95%) Langerhans cells from murine epidermis obtained by the panning method, we investigated whether murine Langerhans cells express CD23. As the result of a series of experiments using fluorescence activated cell sorter analysis and the polymerase chain reaction method, it was revealed that CD23 is expressed on cultured Langerhans cells, but not on freshly isolated Langerhans cells. Comparison of the DNA sequence of polymerase chain reaction products of CD23 from cultured Langerhans cells with that from spleen leukocytes demonstrated that there were the same sequences between the two polymerase chain reaction products. The expression of CD23 on cultured Langerhans cells was downregulated when Langerhans cells were cultured with keratinocyte-derived cytokines: interleukin-1α, interleukin-18, macrophage colony-stimulating factor, or granulocyte-macrophage colony-stimulating factor. Moreover, it was shown that murine IgE bound to cultured Langerhans cells and this binding was partially inhibited when Langerhans cells were cultured with monoclonal antibody against CD23 (B3B4). Thus this study revealed murine cultured Langerhans cells do express CD23 and the discrepancy from previous reports may be due to the influence of cytokines derived from keratinocytes. Furthermore, the finding that murine cultured Langerhans cells bind IgE through CD23 suggests that CD23 on murine Langerhans cells may be involved in IgE-mediated immune responses. [ABSTRACT FROM AUTHOR]

Transmissible spongiform encephalopathies are characterized by the accumulation of a proteinase-resistant isoform of the cellular prion-related protein (PrPc) within the central nervous system (CNS). The accumulation of scrapie-associated PrP (PrPSc) within cells of the lymphoreticular system prior to its accumulation in the CNS is regarded as important for the development of neurological diseases after peripheral inoculation. Little, however, is known as to which cells are the targets for peripheral inoculation. Here, the presence of PrPc on murine Langerhans cells (LC), dendritic cells in the skin and mucosa, and keratinocytes (KC) is demonstrated by immunohistochemical staining, Western-blotting and FACS analysis. The expression of PrPc mRNA in freshly purified LC and KC was also detected by reverse transcriptase-polymerase chain reaction. The expression of PrPc on LC was slightly increased during culture. These data suggest that LC and KC may be the targets for peripheral infection with prions. [Copyright &y& Elsevier]

Summary Langerhans cells are MHC class II antigen-positive antigen-presenting cells in the epidermis. Recent studies have revealed that Langerhans cells express costimulatory molecules like B7–1 and B7–2 and the accessory molecule CD40. Although these molecules are important for the antigen-presenting function of Langerhans cells, little is known about the precise regulation of their expression on purified Langerhans cells. Using a panning technique, we purified epidermal Langerhans cells to around 95% purity. Freshly prepared Langerhans cells (fLC) expressed the mRNA for receptors for M-CSF (cfms), GM-CSF (GM-CSFR), and TNF-α (TNFRII). TNF-α markedly upregulated CD40 and B7–1 expression on Langerhans cells, but not B7–2 expression. GM-CSF moderately upregulated B7–1 and B7–2 expression, and slightly upregulated CD40 expression. M-CSF moderately upregulated B7–1 expression, but did not modulate CD40 or B7–2 expression. Dexamethasone (DEX) markedly inhibited CD40, B7–1, and B7–2 expression on Langerhans cells. Cyclosporin A (CsA) and FK506 slightly inhibited CD40 and B7–1 expression on Langerhans cells, but not B7–2. Furthermore, TNF-α restored the DEX-induced inhibition of CD40 expression on Langerhans cells, but not the inhibition of B7–1 or B7–2 expression. GM-CSF restored DEX-induced inhibition of CD40, B7–1, and B7–2 expression. M-CSF did not affect the DEX-induced inhibition of these molecule expres- sions. These data provide a better understanding of the role of selective cytokines and immunosupressive drugs in the modulation of the antigen-presenting capacity of Langerhans cells. [ABSTRACT FROM AUTHOR]

Presents a letter to the editor in the May 2005 issue of the "Journal of Investigative Dermatology."