published_or_final_version / Paediatrics and Adolescent Medicine / Master / Master of Medical Sciences

Isolation and identification of all yeast species found on skin affected by atopic dermatitis, evaluation of their influence to the synthesis of IgE antibodies, and assessment of the possible cross-reactivity between different yeast species was performed. It was shown that in 36.9 % of the cases of atopic dermatitis, the affected skin was colonized with yeast belonging to three genera: Candida, Malassezia and Rhodotorula. Systematic and phylogenetic analysis of sequences from atypical Malassezia restricta strain M8 indicated that this isolate could be a member of a new yeast species. Three atypical Malassezia isolates M47, M54 and M235 were identified as non-lipid-dependent variants of Malassezia furfur. It was shown that in atopic dermatitis, cutaneous colonization with yeast is two-fold higher in adults than in children. The sera of atopic dermatitis patients have specific IgE antibodies to cross-reactive intracellular yeast antigens. Candida pelliculosa and house dust mites Dermatophagoides pteronyssinus and Dermatophagoides farinae might share some allergenic epitopes. The results of this study suggest that attention should be given to a cutaneous colonization by saprophytic yeast since the immune response to the allergens could further exacerbate allergic inflammation due to cross-reactive epitopes. / Išskirtos ir identifikuotos atopinio dermatito pažeistą odą kolonizuojančios mielių rūšys, įvertinta jų įtaka specifinių IgE antikūnų sintezei bei kryžminių reakcijų tarp skirtingų mielių rūšių galimybė. Nustatyta, kad 36,9 % atvejų atopinio dermatito pažeista oda yra kolonizuojama Candida, Malassezia ir Rhodotorula genties mielėmis. Išskirtas netipinėmis fiziologinėmis savybėmis pasižymintis Malassezia restricta kamienas M8 gali būti naujos rūšies atstovas. Išskirti netipinėmis fiziologinėmis savybėmis pasižymintys Malassezia genties kamienai M47, M54 ir M235 identifikuoti kaip nuo išorinio lipidų šaltinio nepriklausantys Malassezia furfur. Įrodyta, kad mielės suaugusių asmenų atopinio dermatito pažeistą odą kolonizuoja du kartus dažniau negu vaikų. Įrodyta, kad atopiniu dermatitu sergančių asmenų kraujo serume aptinkama prieš kryžmiškai reaguojančius mielių viduląstelinius antigenus nukreiptų specifinių IgE antikūnų. Taip pat nustatyta, kad Candida pelliculosa ir namų dulkių erkių Dermatophagoides pteronyssinus ir Dermatophagoides farinae alergenai gali turėti panašius epitopus. Darbo rezultatai patikimai rodo, kad atopinio dermatito pažeistą odą kolonizuojančios komensalinės mielės gali pasunkinti atopinio dermatito eigą dėl kryžmiškai reaguojančių epitopų tarp skirtingų biologinių rūšių antigenų.

Psoriasiform diseases are a group of cutaneous disorders that are characterized by impaired keratinocyte maturation leading to epidermal hyperplasia and thickening of skin. This group of disorders includes psoriasis, seborrheic dermatitis (SD) and mycosis fungoides (MF). Psoriasis has been recently shown to be mediated by the pro-inflammatory T helper cell subset, namely Th17 cells, whereas the pathogenesis of SD and MF are still poorly understood. SD is characterized by inflamed skin that primarily manifests on areas populated with sebaceous glands. Interestingly, SD is very common amongst immunosuppressed patients such as those with HIV-AIDS, suggesting the importance of an immune response in the development of SD. Because SD shares common clinical and histopathological features with psoriasis, a disease in which Th17 axis cytokines is known to be involved, and given that Th17 cells and their related cytokines have been implicated in the pathogenesis of a wide range of autoimmune and inflammatory disorders, it is possible that Th17 axis cytokines play a role in the pathogenesis of SD. We explored the involvement of Th17 axis cytokines in a D2C mouse model of psoriasiform disease that shows a high degree homology to the clinicopathological characteristics of human seborrheic dermatitis. IL-6 and IL-23, which are important for the differentiation of Th17 cells, and IL-17 and IL-22, which are the Th17 effector molecules, were measured at both protein and mRNA levels in sera and lesional skin from D2C mice. An immunohistochemical analysis was also performed to detect the presence of IL-17 in D2C lesional skin relative to normal skin from DBA/2 controls. Our data demonstrated significantly elevated levels of IL-6, IL-17 and IL-22 in sera from diseased D2C mice compared to controls and/or convalescent mice. There were no significant differences in IL-23 protein levels in sera from D2C mice compared to those from wild type mice or convalescent D2C mice. RT-PCR revealed a significant increase in IL-23 and IL-17 gene expression in D2C lesional skin relative to normal skin. Gene expression levels of IL-22, but not IL-6, were statistically significant elevated in D2C skin lesions compared to controls, by real time PCR. Our IHC study of IL-17 expression showed an abundance of positively stained mononuclear cells in D2C lesional skin relative to DBA/2 normal skin. Altogether, our data demonstrate that Th17 axis cytokines are elevated locally at mRNA levels for IL-23, IL-17, and IL-22 and systematically at protein levels for IL-6, IL-17, and IL-22. This data lay the foundation for further studies investigating a role for Th17 axis cytokines in the cutaneous inflammatory disease seen in our mouse model of SD and, ultimately, in the development of human SD. Mycosis fungoides (MF) is the most common type of cutaneous T cell lymphoma (CTCL). The etiology of MF is unknown, but there is substantial evidence suggesting a potential role for a yet unidentified infectious agent in the pathogenesis of MF. Many studies have claimed that there is an association between MF and the Human T cell Lymphotorpic Virus Type 1 (HTLV-I); however, the involvement of this virus in the etiology of MF is a controversial topic. In our study, we used nested PCR to explore the association between HTLV-I infection and MF by screening genomic DNA from 114 skin biopsies for the presence of HTLV-I provirus. We also utilized a ViroChip and high-throughput sequencing (HTS), as a case study, to attempt to detect novel virus-specific oligonucleotides that may be associated with CTCL. Our data showed no evidence for HTLV-I proviral integration in the 114 MF samples that were screened using nested-PCR. The ViroChip and HTS results also did not reveal any signature sequence for known or unknown infectious agent in the CTCL case study. Collectively, this data argue against the involvement of HTLV-I provirus in the pathogenesis of MF.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2007. / Härtill 4 uppsatser.

Mémoire (M.Med.Exp.)--Université du Québec à Chicoutimi, 2000. / Document électronique également accessible en format PDF. CaQCU

Em função de modificações no processo de criação em escala industrial, associado à expansão do setor avícola nas áreas de genética, nutrição e sanidade, as lesões cutâneas em frangos de corte vêm tornando-se cada vez mais importantes. Na atualidade, as principais doenças que afetam a pele de frangos são a celulite, a varíola aviária, o querato-acantoma (QA) ou carcinoma dérmico de células escamosas (CDCE) e as dermatites inespecíficas, estas últimas geralmente associadas a traumatismos. A classificação das doenças cutâneas é imprecisa, uma vez que os critérios de inspeção tendem a agrupar essas lesões cutâneas nas carcaças de frangos de corte em uma única categoria denominada de “dermatose”. As lesões ulcerativas na pele de frangos de corte são causas comuns de condenação total ou parcial de carcaças em matadouros-frigoríficos. O querato-acantoma é uma das causas mais frequentes dessas lesões, sendo de etiologia desconhecida. Por outro lado, lesões ulcerativas macroscopicamente semelhantes às do querato-acantoma e causadas por granulomas do tipo corpo estranho, possivelmente de origem vegetal, vêm sendo observadas em aves abatidas em alguns matadouros-frigoríficos no estado do Rio Grande do Sul (Brasil). Com base nessas premissas, o objetivo desse trabalho foi avaliar histologicamente e analisar os fatores epidemiológicos envolvidos no aparecimento das lesões ulcerativas cutâneas: querato-acantoma e dermatite granulomatosa por corpo estranho (DGCE) em frangos de corte abatidos em matadouros-frigoríficos sob inspeção federal e estadual. Foram analisadas 363 amostras com lesões ulcerativas, de um total de 1.373.989 aves visualizadas. Destas, 169 carcaças foram diagnosticadas como querato-acantoma, representando uma prevalência de 0,012% e 210 carcaças foram diagnosticadas como dermatite granulomatosa por corpo estranho, representando 0,015%, A prevalência encontrada no presente trabalho para QA é similar aos valores encontrados por autores, já a prevalência encontrada para DGCE foi superior à relatada em 2004. Se verificou uma maior prevalência de QA em frangos abatidos em matadouros-frigoríficos sob inspeção federal e mais casos de DGCE nos abatidos em matadouros-frigoríficos sob inspeção estadual. A localização mais frequente das úlceras foi o dorso para o querato-acantoma e o peito para a DGCE. As lesões ulcerativas disseminadas na carcaça foram 100 % diagnosticadas como querato-acantoma. Macroscopicamente as lesões únicas podem ser tanto diagnósticas para querato-acantoma como dermatite granulomatosa por corpo estranho, sendo necessário o exame histopatológico para o diagnóstico definitivo. Houve grande variabilidade dos fatores epidemiológicos envolvidos no aparecimento de lesões ulcerativas de pele, indicando necessidade de novas análises para aumentar a amostragem das amostras. / Due to changes in the husbandry process on an industrial scale, associated with the expansion of the poultry sector in the areas of genetics, nutrition and health, the skin lesions have become increasingly important. At present, the major diseases that affect the skin in broilers are cellulite, fowl pox, the keratoacantoma (KA) or dermal squamous cell carcinoma (DSCC) and nonspecific dermatitis, the latter generally associated with trauma. The classification of skin diseases is inaccurate, since the inspection tend to group these skin lesions in carcasses of broilers in a single category called "dermatosis". The ulcerative skin lesions of broilers are common causes of total or partial condemnation of carcasses in slaughterhouses. The keratoacantoma is one of the most frequent causes of these injuries, and of unknown etiology. On the other hand, ulcerative lesions macroscopically similar to the keratoacantoma and granulomas caused by foreign body, possibly of plant origin, has been observed in some birds slaughtered in slaughterhouse in Rio Grande do Sul (Brazil). Based on these premises, the aim of this study was to histologically evaluate and analyze the epidemiological factors involved in the appearance of ulcerative skin: keratoacantoma and foreign body granulomatous dermatitis (FBGD) in broilers slaughtered in slaughterhouses under federal and state inspection. 363 samples were analyzed with ulcerative lesions, a total of 1,373,989 poultry displayed. Of these, 169 carcasses were diagnosed as keratoacantoma, representing a prevalence of 0.012% and 210 carcasses were diagnosed as granulomatous dermatitis foreign body, representing 0.015%. The prevalence founded in the present work to KA is within the range found by authors in previous works, since the prevalence DSCC was higher than that reported in 2004. There was a higher prevalence of KA in slaughter plants under federal inspection and more cases of DSCC in slaughter plants under state inspection. The most frequent location of ulcers was the back and chest for keratoacantoma for DSCC. Ulcerative lesions disseminated in the housing 100% were diagnosed as keratoacanthoma. Grossly, the lesions can be both unique diagnostic for keratoacanthoma as granulomatous dermatitis, requiring histopathology for definitive diagnosis. With this work, it was concluded that new skin lesions should be analyzed, to increase the sampling of specimens, decreasing the variability among the predisposing skin lesions.

La dermatite atopique est une dermatose inflammatoire apparaissant préférentiellement avant l’âge de cinq ans, et évoluant naturellement vers la guérison après l’adolescence dans plus de 90% des cas. L’origine de cette amélioration spontanée n’est pas clairement établie dans cette dermatose multifactorielle dont l’étiopathogénie reste encore à déterminer (maturation du système immunitaire ?). Les liens de cette pathologie avec le psychisme sont certains : retentissement psychologique important avec altération de la qualité de vie, aggravation voire déclenchement des poussées par le stress, amélioration des lésions par psychothérapie. L’observation de la nature de la structure d’attachement est importante dans le domaine de la psychopathologie. Elle est encore peu réalisée dans le domaine da la pathologie organique. Nous avons étudié la structure d’attachement de 80 adultes ayant présenté dans l’enfance une dermatite atopique, 40 d’entre eux ayant une guérison de celle-ci depuis l’adolescence, 40 autres présentant une pérennisation des crises d’eczéma. L’évaluation de l’attachement a été réalisée avec un autoquestionnaire (CAMIR de PIERREHUMBERT) et la cotation de l’entretien d’attachement avec la méthode Q-SORT selon KOBAK. Nous avons également mesuré les symptômes psychopathologiques associés avec l’échelle SCL90-R, le niveau d’anxiété avec l’inventaire trait-état de SPIELBERGER (STAIY) et le coping avec le WCC-R de VITALIANO. Les IgE totales ont été dosées. Les sujets avec dermatite atopique ayant débutée avant trois ans ne sont pas plus insécures que ceux avec un début plus tardif de leur dermatose. Ceci fait évoquer la possibilité d’une absence de retentissement sur la structure d’attachement d’une dermatite atopique apparaissant dans les premiéres années de vie, contrairement à ce qui est noté dans toute pathologie chronique d’apparition précoce. Il est alors supposé un effet positif des soins cutanés sur la nature de la relation de la dyade mère-enfant. Par contre, le retentissement ultérieur de la dermatite atopique chez l’adulte est important, avec augmentation d’une insécurité préoccupée en termes de représentations d’attachement, une augmentation des scores de toutes les dimensions psychopathologiques mesurées et une recherche anxieuse de soutien à l’extérieur. Ce retentissement est d’autant plus important que les IgE sont élevées, ceci n’étant pas uniquement le reflet de la gravité de la maladie. Les adultes présentant une dermatite atopique pérennisée sont structurellement plus insécures que ceux qui ont guéris : si nous considèrons l’aspect stable dans le temps de la structure d’attachement, ces résultats positionneraient celle ci en tant que possible facteur dispositionnel prédictif dans l’évolution de la dermatite atopique. Le score de sécurité des patients guéris est d’autant plus élevé que les IgE sont normales. Un phénomène d’interaction entre le système d’attachement et le système adaptatif au stress, à dépendance développementale commune sur certains aspects, est évoqué. Le rôle des IgE reste à déterminer. En termes de psychologie de la santé, la structure d’attachement pourrait être considérée comme un facteur dispositionnel susceptible d’influer l’évolution de la dermatite atopique. / Atopic dermatitis is an inflammatory skin disorder which usually appears before the age of five, and heals naturally little by little after adolescence in over 90% of cases. Why this spontaneous improvement occurs is not clearly established for this multi-factor skin disorder, for which the etiopathology has yet to be determined (immune system maturity?).There is a clear relationship between this pathology and the psyche: major psychological repercussions affecting the quality of life, aggravation or triggering of skin reactions due to stress, alleviation of lesions using psychotherapy. Observation of patterns of attachment is important in the field of psychopathology, but is not often undertaken in the domain of organic pathology. We studied the patterns of attachment for 80 adults having suffered from atopic dermatitis during childhood, 40 of them had been cured since adolescence, the other 40 continued to suffer from outbreaks of eczema. Attachment was evaluated using a self-completion questionnaire (CAMIR by PIERRE HUMBERT) and the attachment interview was graded using the Q-SORT method, by KOBAK. We also measured the associated psychopathological symptoms using the SCL90-R scale, level of anxiety using SPIELBERGER’s state-trait-anxiety inventory (STAIY), and coping measurement using the WCC-R scale devised by VITALIANO. Total IgE was measured. Patients suffering from atopic dermatitis that began before the age of 3 years are not more insecure than patients whose skin disorder started later in life. This meant that there were possibly no repercussions on the pattern of attachment for cases of atopic dermatitis that had appeared in the first years of life, contrary to all reports regarding a chronic pathology appearing early in life. This implies that caring for the skin has a positive effect on the mother-child relationship. On the other hand, adults suffer from major repercussions of atopic dermatitis later on in life: increased sense of preoccupied insecurity in terms of representations of attachment, increased scores in all the psychopathological dimensions measured, and an anxious need for outside support. These repercussions are even more serious when IgE is high, but this is not solely connected with the gravity of the illness. Adults suffering from persistent atopic dermatitis are basically more insecure than those who are cured: if long-term stability in the pattern of attachment is considered, this study could place pattern of attachment as a possible predictive disposition factor in the evolution of atopic dermatitis. The security score of cured patients is all the greater when IgE is normal. The existence of an interaction between the attachment pattern and the system for adapting to stress has been suggested, since they are both dependent on development. The role played by IgE remains to be determined. In terms of health psychology, the pattern of attachment could be considered as a disposition factor likely to influence the evolution of a skin disorder.

L'allergie de contact est une pathologie en constante augmentation et particulièrement répandue dans les pays industrialisés. Aucune thérapie n'existe actuellement et seule l'éviction totale de l'allergène permet d'éviter toute nouvelle réaction d'allergie. La base de l'allergie de contact est la formation d'une liaison entre l'allergène et les protéines épidermiques. C'est cette étape chimique clé qu' il est important de comprendre afin de développer de nouvelles méthodes dites« alternatives» dans le cadre de l'actuelle législation sur les cosmétiques. Le but de ce travail de thèse a été d'étudier la réactivité de différents allergènes connus face aux acides aminés et protéines d'épidermes reconstruits de type SkinEthic® par la technique RMN HRMAS dérivée de la RMN du solide. Six allergènes ont ainsi été étudiés et leur réactivité a été comparée a celle observée en solution face à une protéine modèle. / Contact dermatitis is one of the most common health problem and highly prevalent in industrialized countries. No therapy currently exists and only the total eviction of the allergen can prevent further allergie reaction.The key molecular event in skin sensitization is the formation of a bond between the allergen and the epidermal proteins. Due to the recent legislation on cosmetic and to help avoid the inappropriate use of new allergens, the understanding of this key step has to be expanded in order to develop new alternative metbods.The aim of this PhD work is to study the reactivity of some allergens towards amino acids and proteins presents in reconstructed human epidermis like SkinEthic® using the HRMAS NMR technique. Six allergens have been studied and their reactivity was compared to that observed ln solution with a model protein.

Em função de modificações no processo de criação em escala industrial, associado à expansão do setor avícola nas áreas de genética, nutrição e sanidade, as lesões cutâneas em frangos de corte vêm tornando-se cada vez mais importantes. Na atualidade, as principais doenças que afetam a pele de frangos são a celulite, a varíola aviária, o querato-acantoma (QA) ou carcinoma dérmico de células escamosas (CDCE) e as dermatites inespecíficas, estas últimas geralmente associadas a traumatismos. A classificação das doenças cutâneas é imprecisa, uma vez que os critérios de inspeção tendem a agrupar essas lesões cutâneas nas carcaças de frangos de corte em uma única categoria denominada de “dermatose”. As lesões ulcerativas na pele de frangos de corte são causas comuns de condenação total ou parcial de carcaças em matadouros-frigoríficos. O querato-acantoma é uma das causas mais frequentes dessas lesões, sendo de etiologia desconhecida. Por outro lado, lesões ulcerativas macroscopicamente semelhantes às do querato-acantoma e causadas por granulomas do tipo corpo estranho, possivelmente de origem vegetal, vêm sendo observadas em aves abatidas em alguns matadouros-frigoríficos no estado do Rio Grande do Sul (Brasil). Com base nessas premissas, o objetivo desse trabalho foi avaliar histologicamente e analisar os fatores epidemiológicos envolvidos no aparecimento das lesões ulcerativas cutâneas: querato-acantoma e dermatite granulomatosa por corpo estranho (DGCE) em frangos de corte abatidos em matadouros-frigoríficos sob inspeção federal e estadual. Foram analisadas 363 amostras com lesões ulcerativas, de um total de 1.373.989 aves visualizadas. Destas, 169 carcaças foram diagnosticadas como querato-acantoma, representando uma prevalência de 0,012% e 210 carcaças foram diagnosticadas como dermatite granulomatosa por corpo estranho, representando 0,015%, A prevalência encontrada no presente trabalho para QA é similar aos valores encontrados por autores, já a prevalência encontrada para DGCE foi superior à relatada em 2004. Se verificou uma maior prevalência de QA em frangos abatidos em matadouros-frigoríficos sob inspeção federal e mais casos de DGCE nos abatidos em matadouros-frigoríficos sob inspeção estadual. A localização mais frequente das úlceras foi o dorso para o querato-acantoma e o peito para a DGCE. As lesões ulcerativas disseminadas na carcaça foram 100 % diagnosticadas como querato-acantoma. Macroscopicamente as lesões únicas podem ser tanto diagnósticas para querato-acantoma como dermatite granulomatosa por corpo estranho, sendo necessário o exame histopatológico para o diagnóstico definitivo. Houve grande variabilidade dos fatores epidemiológicos envolvidos no aparecimento de lesões ulcerativas de pele, indicando necessidade de novas análises para aumentar a amostragem das amostras. / Due to changes in the husbandry process on an industrial scale, associated with the expansion of the poultry sector in the areas of genetics, nutrition and health, the skin lesions have become increasingly important. At present, the major diseases that affect the skin in broilers are cellulite, fowl pox, the keratoacantoma (KA) or dermal squamous cell carcinoma (DSCC) and nonspecific dermatitis, the latter generally associated with trauma. The classification of skin diseases is inaccurate, since the inspection tend to group these skin lesions in carcasses of broilers in a single category called "dermatosis". The ulcerative skin lesions of broilers are common causes of total or partial condemnation of carcasses in slaughterhouses. The keratoacantoma is one of the most frequent causes of these injuries, and of unknown etiology. On the other hand, ulcerative lesions macroscopically similar to the keratoacantoma and granulomas caused by foreign body, possibly of plant origin, has been observed in some birds slaughtered in slaughterhouse in Rio Grande do Sul (Brazil). Based on these premises, the aim of this study was to histologically evaluate and analyze the epidemiological factors involved in the appearance of ulcerative skin: keratoacantoma and foreign body granulomatous dermatitis (FBGD) in broilers slaughtered in slaughterhouses under federal and state inspection. 363 samples were analyzed with ulcerative lesions, a total of 1,373,989 poultry displayed. Of these, 169 carcasses were diagnosed as keratoacantoma, representing a prevalence of 0.012% and 210 carcasses were diagnosed as granulomatous dermatitis foreign body, representing 0.015%. The prevalence founded in the present work to KA is within the range found by authors in previous works, since the prevalence DSCC was higher than that reported in 2004. There was a higher prevalence of KA in slaughter plants under federal inspection and more cases of DSCC in slaughter plants under state inspection. The most frequent location of ulcers was the back and chest for keratoacantoma for DSCC. Ulcerative lesions disseminated in the housing 100% were diagnosed as keratoacanthoma. Grossly, the lesions can be both unique diagnostic for keratoacanthoma as granulomatous dermatitis, requiring histopathology for definitive diagnosis. With this work, it was concluded that new skin lesions should be analyzed, to increase the sampling of specimens, decreasing the variability among the predisposing skin lesions.

Atopic dermatitis (AD) is a common, chronic relapsing inflammatory skin disease associated with cutaneous hyper-reactivity to environmental triggers that are innocuous to normal nonatopic individuals. AD affects 10% to 15% of children and 2% to 10% of adults in industrialized countries. There has been increasing interest in this disease triggered by its increasing prevalence in western societies and its contribution to the increasing health care costs. Yet, the underlying pathophysiologic and genetic mechanisms leading to the manifestation of AD are not clear. AD results from a complex interplay between environmental triggers, susceptibility genes including mutations in the keratinocyte protein filaggrin and altered immune responses resulting in allergic CD4+ T cell (Th2) immunity to epidermally encountered antigens. Regulatory T cells (Tregs) play an important role in controlling responsiveness to self-antigens and preventing autoimmune diseases, as well as in limiting inflammatory responses during inflammation and infection. Currently, studies investigating the number and function of Tregs in patients with AD have shown controversial results. It has been long established that symptoms of AD improve on exposure to sunlight. Narrowband UVB (NB-UVB) phototherapy is a common treatment modality for a variety of skin diseases. Considering the adverse effects for systemic treatment for severe adult AD, phototherapy, especially NB-UVB phototherapy may be a more practical long-term treatment. However, approximately 50% of patients over an 8-week treatment course do not improve after NB-UVB phototherapy. Therefore, it is important to identify characteristics of AD patients to determine whether they will respond to phototherapy and to avoid adverse effects for unresponsive patients. UVB exposure has also been associated with induction of Tregs in mice and increasing their numbers and/or functional capacity may offer benefit to patients with chronic AD. Active vitamin D (1,25(OH)2D3), one of the factors induced by UV-B radiation induces Tregs and is suggested to contribute to the suppressive effect of NB-UVB phototherapy. However, UV radiation could also have beneficial effects through other pathways known to affect immunoregulation. UVB exposure upregulates production of nitric oxide (NO) in the skin which also affects immune cell function. The protein filaggrin is broken down in differentiating keratinocytes to form the natural moisturizer of the skin. The gene encoding filaggrin (FLG) has been shown to be a major predisposing factor for AD. A key breakdown product is urocanic acid (UCA) which also acts as a natural sunscreen and undergoes trans-cis isomerisation on exposure to UV-B. Cis-UCA is known to modulate immune responses, however, the mechanisms of its action remain elusive. The production of all three compounds, vitamin D, cis-UCA and NO might all increase in the circulation of patients undergoing UVB phototherapy. While the immunomodulatory effect of Vitamin D is well described, cis-UCA and NO may also affect the behaviour of T lymphocytes systemically. Therefore, I investigated the effect of NO and cis-UCA on the phenotype and function of CD4+T cells and monocyte-derived dendritic cells (Mo-DCs) derived from peripheral blood mononuclear cells (PBMCs) from healthy volunteers. I also investigated the correlation between plasma concentration of 25(OH) vitamin D and nitrate, FLG genotype, circulating Tregs and clinical efficacy of NB-UVB phototherapy. My results showed that NO did not affect the phenotype of human mo-DCs and directly affected peripheral CD4+ T cells by inducing functional CD25+Foxp3+CD127-Tregs from CD4+CD25lo/- effector T cells. Moreover, NO increased expression of the of skin homing marker CLA on these Tregs, suggesting an increased ability of NO-induced Tregs to migrate to the skin. These NO-induced CD25+Foxp3+CD127-Tregs had immunosuppressive functions and inhibited autologous CD4+ T cell proliferation. Cytokines, at least IL-10, secreted by NO-treated CD4+ T cells were not sufficient for the suppressive function of NOinduced Foxp3+Tregs. The immune regulatory function of NO-induced Fopx3+Tregs required cell-cell contact and was mediated by membrane bound TGFβ and PD-1/PD-L1 but not CTLA-4. Results also showed that cis-UCA might have both pro- and anti-inflammatory effects. Cis- UCA significantly decreased the proportion of CD25hi Foxp3+ cells from activated CD4+ T cells. It also decreased the expression of vitamin D receptor in CD4+ T cells which may interfere with the immune regulatory function of vitamin D. These results suggested that there might be a fine balance between UV-induced anti-inflammatory molecules’ effect on CD4+ T cells. However, Cis-UCA also modulated CD4+ T cell directly by decreasing CD4+ T cell proliferation, decreasing phosphorylation of ERK after TCR activation, enhancing immune suppressive cytokines secretion, and inhibiting the percentage of CLA+CD4+T cells suggesting a decreased ability to migrate to the skin, . Cis-UCA also affected the phenotype and function of antigen presenting cells by decreasing the expression of HLA-DR, CD86 and CD40 on immature mo-DCs, which led to increased proportion of CD25+Foxp3+CD127- T cells when co-cultured with allogenic CD4+ T cells. Results generated from the clinical study in which all 29 patients got better after phototherapy suggested although circulating 25 (OH) vitamin D concentration was significantly increased after NB-UVB phototherapy, the change of circulating 25 (OH) vitamin D concentration did not correlate with disease improvement. This suggests that vitamin D is not the only pathway involved and that other molecules contribute to UVB-induced immune-regulation. The data also show that of the levels of circulating nitrate and the FLG genotype did not correlate with improvement / change with phototherapy. However, the expression of CD69 and CLA on circulating CD4+ T cells was decreased after treatment suggesting that UVB affected T cell activation and migration to the skin, and their importance in determining clinical responses requires further investigation. Taken together, the results from my study provide evidence that vitamin D is not the only molecule responsible for the beneficial effect of NB-UVB phototherapy. NO and cis-UCA may down-regulate immune responses by affecting human peripheral CD4+ T cells and mo- DCs phenotype and function. A further understanding of the effect of NO and cis-UCA on skin resident immune cells will provide more insights for narrowing NB-UVB phototherapy which will help to select patients that most likely to benefit from a mechanism-based treatment.