Thesis supervisor: Annette J. Schlueter. Includes bibliographic references (p. 106-116).

Thesis (doctoral)--Lund University, 1994. / Added t.p. with thesis statement inserted.

Thesis (doctoral)--Lund University, 1994. / Added t.p. with thesis statement inserted.

Allergic contact dermatitis is an important occupational health disease. It represents a useful experimental paradigm in which the mechanisms and characteristics of cutaneous immune responses can be investigated. This thesis has focused on the sensitization phase of contact allergy, including Langerhans’ cell (LC) migration, cytokine expression and the ability of the protein lactoferrin (LF) to modulate aspects of these processes. Lactoferrin was originally identified as an antimicrobial protein. However, it is being recognized increasingly to have immunomodulatory effects on the cells of the immune system. Migration of LC in mice and in humans is mediated via two independent cytokine signals delivered by tumour necrosis factor (TNF)-α and interleukin (IL)-1β, which were thought to derive from keratinocytes and LC, respectively. Further, topical application of LF was shown to inhibit LC migration in both man and mouse potentially through the inhibition of de novo TNF-α production. The inhibitory effect of LF on LC mobilization induced by the contact allergen 4-ethoxymethylene-2-phenyl-2-oxazolin-5-one (oxazolone) has been confirmed in these investigations. Conversely, LF did not inhibit LC migration triggered by another contact allergen, 2,4-dinitrochlorobenzene (DNCB). That result prompted a comparison between oxazolone and DNCB with respect to their ability to induce LC migration and to provoke cutaneous cytokine production. It was discovered that DNCB induced LC mobilization in the absence of TNF-α signalling. Moreover, exposure to superoptimal doses of oxazolone resulted in TNF-α independent LC migration. Further experiments revealed that TNF-α independence might be mediated partially by the elevated concentration of IL-1β produced in the skin following exposure to DNCB and these superoptimal concentrations of oxazolone. Investigations of the immunomodulatory mechanism of LF in vitro demonstrated that it did not inhibit TNF-α production by THP-1 macrophages. On the contrary, LF was shown to stimulate TNF-α and IL-8 release by THP-1 macrophages in a dose dependent manner, via endotoxin-independent and nucleolin-dependent mechanism. Subsequently, the role of LF in modulation of keratinocyte activation was investigated. Keratinocytes expressed high levels of inducible TNF-α mRNA, however, this was not modulated specifically by LF. Additional examination of the effects of LF in vivo revealed that it inhibited cutaneous IL-17 and CXCL1 mRNA expression, induced by IL-1β and IL-1α, respectively. Lactoferrin treatment did not affect oxazolone-induced lymph node (LN) cell proliferation. However, it was demonstrated to decrease IL-17 production by LN cells 24h following exposure to oxazolone, which may be important in driving the vigour and/or quality of response to the contact allergen. Overall, these investigations have demonstrated a divergence within the family of contact allergens with regard to the requirement for TNF-α signalling for LC mobilization. It was established that when elevated concentrations of IL-1β are present LC migration can occur in the absence of TNF-α signalling. Moreover, a dual nature of LF, which can act in a stimulatory as well as inhibitory manner, was confirmed. These investigations have revealed a potential role for CXCL1 and IL-17 in the process of LC migration. Furthermore, it was shown that the inhibitory effect of LF on oxazolone induced LC migration might be mediated via its effect on IL-17.

Mature dendritic cells (DC) isolated from lymphoid tissues initiate antigen-specific T-dependent responses even though they are non-phagocytic and weakly pinocytic, whereas Langerhans cells (LC; immature DC) can process protein antigens but are poorly immunostimulatory. Thus antigens may be acquired by cells of this lineage at an immature stage but, to our knowledge, there have been no studies on the phagocytic capacity of these cells in vitro. Using a newly-developed flow cytometric assay to measure the association between fluorescent markers and LC in epidermal cell cultures, and light and electron microscopy, we have observed phagocytosis of a variety of particles by freshly-isolated LC. The cells readily phagocytosed zymosan, heat-killed S. cerevisiae, bacteria (S. aureus and C. parvum) and fluorescent latex beads, but were unable to take up IgG- or complement-coated sheep erythrocytes, as opposed to MØ. Similarly, many freshly-isolated splenic DC had some phagocytic activity. However, the capacity of both LC and splenic DC to phagocytose zymosan, bacteria and fluorescent latex beads was markedly decreased after maturation in culture, consistently with the fact that mature DC are poorly phagocytic. Zymosan binding and uptake were much greater in fresh LC from C57BL/6 compared to BALB/c mice, and the loss of phagocytic capacity for zymosan during maturation followed different kinetics in the two strains. Two receptors mediating uptake of zymosan in LC were identified based on the effect of different inhibitors. Both of these receptors, recognising mannose and β-glucan residues, appear to be differentially regulated in the two mouse strains and during culture of LC. Our findings support the notion that DC are capable of acquiring particulate antigens for presentation at an immature stage, through recognition units for carbohydrate determinants common to a variety of potentially pathogenic organisms.

Thesis (M.S.)--University of Michigan, 1986.

Thesis (M.S.)--University of Michigan, 1986.

Magister Scientiae (Medical Bioscience) - MSc(MBS) / Athymic nude mouse models have been extensively used to study biological behaviour of normal and diseased human tissues. In such models, immune-deficient mice act as hosts for cysts constructed from human material. A unique biocyst model that entails transplantation of human vaginal cysts into athymic nude mice has been implemented to study diseases of oral mucosa. To date, only one immunohistochemical study of this biocyst model has been reported. Nevertheless, conclusions made in that study were only based on the observed expression patterns of human and murine markers. Statistical assessment of immunohistochemical data had been omitted by the investigator. Therefore, the objective of this study was to further delineate the immunohistochemical profile of normal human vaginal tissue and human vaginal tissue that had been xenografted into nude mice.Experimental cysts constructed from human vaginal mucosa were xenografted into athymic nude mice and harvested 9-weeks post transplantation. Immunohistochemical analysis of normal human vaginal tissue and human vaginal tissue that had been xenografted into nude mice was performed using a panel of human and murine markers. Expression patterns of human and murine markers were assessed. Human markers included cytokeratin 1,cytokeratin 5, cytokeratin 13, cytokeratin 14, collagen type IV, laminin, elastin, fibronectin,Langerhans cells and VEGFR-3. Murine markers included collagen type IV, laminin,fibronectin, Langerhans cells and VEGFR-2. Staining intensities were quantified and statistically analysed using one-way ANOVA with subsequent Friedman’s test for multiple comparisons. Since the sample size was small, the power of the test statistic was enhanced by including Dunn’s post-test for further multiple comparisons. A strong positive expression of all cytokeratins was detected in both normal and xenografted vaginal tissues. Human markers that exhibited weak to moderate positive expression were collagen IV, laminin, fibronectin and VEGFR-3. Human elastin and human Langerhans cells exhibited strong and varying expression patterns respectively. Weak expression patterns for all murine markers were reported, with an exception of VEGFR-2 which was negatively expressed in all xenografted vaginal tissues. Significant differences (P<0.05) in the mean staining intensities between normal and xenografted vaginal tissues were reported for cytokeratin 1, fibronectin and Langerhans cells. There were no statistical differences (P>0.05) in the mean staining intensities for other markers.In conclusion, immunohistochemical studies proved that human vaginal tissue could not only survive in nude mice, but could also become active and develop structures necessary for survival, in this case, a newly formed stromal layer. The epithelium and stromal layer exhibited a human ecosystem.

Transmissible spongiform encephalopathies (TSEs), or prion diseases, are fatal neurodegenerative diseases that affect several species, such as scrapie in sheep or goats and CJD in humans. In several species, neurological disease is preceded by TSE agent accumulation in lymphoid tissues prior to neuroinvasion. While oral transmission is considered the most common route for scrapie, transmission can also occur through lesions to the skin or mucosa, for example in the mouth or gastrointestinal tract due to rough feed, or birth associated skin damage. Scrapie has also been experimentally transmitted through skin scarification in mice. Following scrapie infection via skin scarification, PrPSc accumulates in the draining lymph node (LN) before spreading to other organs in the lymphoreticular system. It is not yet known by what means the scrapie agent is transported from the skin to the draining LN. Dendritic cells (DCs) in the skin have been found to transport viruses, such as HIV or Dengue, from the skin, thereby raising the question whether DCs or Langerhans cells (LCs), located within the epidermis, play a role in the uptake and transport of the TSE agent from the skin to the draining LN. CD11c is a cell surface marker traditionally used to identify or isolate DCs from other cell types. Mice and rats are naturally resistant to Diphtheria toxin (DTX). A transgenic mouse line was created where the Diphtheria toxin receptor (DTR) was expressed on CD11c+ cells. The presence of this receptor on CD11c+ cells allowed for the temporary conditional depletion of CD11c+ cells following a single injection of DTX. The cells repopulate the tissues within a time frame specific to the tissues the cells are located in. These mice were used to determine whether the absence of CD11c+ cells at the time of scrapie infection via the skin had an effect on the early accumulation of PrPSc within the lymphoid tissues and on disease progression. Immunohistochemical analysis demonstrated that early PrPSc accumulation in the draining LNs was delayed following depletion of CD11c+ cells, indicating that their potential role in the transport of the scrapie agent from the skin. Scrapie incubation period was not affected by the absence of the CD11c+ cells at the time of infection. Recent findings show that CD11c is not exclusive to DCs and is also expressed on macrophage populations. Following DTX-mediated depletion, DCs repopulate the tissues much faster than CD11c+ macrophages. Scrapie infection was carried out in the skin in DTX treated mice after DCs had repopulated the tissues but before macrophage numbers had returned, to determine whether macrophages rather than DCs played a role in the early accumulation of PrPSc in the draining LNs. No differences in PrPSc accumulation were observed in mice depleted of macrophages compared to controls and there was no effect on disease incubation period. Another transgenic mouse line was used, where DTX expression on langerin+ cells (LCs and langerin+ DCs in the dermis), allowed for their temporary depletion through DTX treatment. Following langerin+ cell depletion, increased PrPSc accumulation was observed in the draining LNs 7 weeks post infection, but did not affect the incubation period of disease. These results indicate that the absence of LCs somehow accelerated PrPSc accumulation, and that LCs might play a preventative role in early stages after infection. Histopathological analysis was used to complement microarray studies aimed to determine what immune responses were associated with scarification and DTXmediated depletion of cells within the skin and whether these responses might be linked to disease transmission. DCs and LCs in the skin appear to play different roles in the early stages following scrapie infection via the skin, but the lack of effect on incubation period does not rule out the involvement of other cell types or cell-free mechanisms of scrapie agent spread from the skin.

A pele é o maior órgão do corpo humano e constitui a principal defesa do organismo contra agentes físicos e químicos, sendo também fundamental para evitar a perda de água por dessecação. Formada por três camadas distintas, mas complementares, sendo as duas principais denominadas derme e epiderme, contendo diferentes tipos celulares, como fibroblastos, queratinócitos, melanócitos, células de Merkel e células de Langerhans, sendo que estas últimas desempenham um papel fundamental na hipersensibilidade de contato. Devido à importância da manutenção da pele saudável para a vida humana, existe uma crescente necessidade da elaboração de substitutos de tecidos para o tratamento de feridos e doentes, assim como, há grande demanda de pele para testes químicos das áreas farmacêutica e cosmética. Outro fator de fundamental importância para o desenvolvimento de métodos alternativos in vitro, é a pressão mundial para que estes testes substituam os modelos animais. Esta abordagem vai de encontro aos novos conceitos de substituição, redução e refinamento na utilização de animais em estudos científicos, ditando o futuro da cultura celular e bioengenharia de tecidos. Graças ao grande desenvolvimento do cultivo celular e descoberta de que as células cultivadas podem ser reagrupadas de acordo com o delineamento experimental, se torna possível à criação de equivalentes dermoepidérmicos para estudos in vitro, como por exemplo, testes de cito e fototoxicidade ou avaliação da fase inicial da reação alérgica e processos de sensibilização da pele. Neste caso, se faz necessária a obtenção de grande quantidade de células de Langerhans imaturas. As células de Langerhans (CLs) são células dendríticas imaturas localizadas na epiderme e epitélio superficial que desempenham um papel central na imunidade da pele, agindo como verdadeiras sentinelas capazes de captar antígenos de contato. Desta forma, foram testados quatro diferentes protocolos para extração e criopreservação destas células, sendo ainda analisadas as suas características morfológicas e fenotípicas. Obtivemos resultados não expressivos quanto ao isolamento, pureza e marcação positiva para CD1a no Protocolo 2 (Expansor de Pele). Os Protocolo 1A (Coleta de Sobrenadante) e 3 (Epiderme + Gradiente de Ficoll Paque) ofereceram altos níveis de células marcadas positivamente para CD1a, apresentando a mesma qualidade de marcação. No entanto, o Protocolo 3 forneceu um maior número de células viáveis, e uma maior pureza da amostra, uma vez que só utiliza a epiderme para a obtenção da suspensão de células, o que o coloca como modelo a ser seguido em posteriores experimentos. Os métodos aqui apontados como mais promissores, podem ser reproduzidos em laboratórios de cultura celular convencionais, contribuindo para aumentar a reprodutibilidade e confiabilidade de resultados experimentais relativos às CLs. Da mesma forma, avaliamos a utilização dos equivalentes de pele humana para a realização de testes in vitro de cito e fototoxicidade, os quais podem de fato reduzir a utilização de modelos animais para identificação do perfil tóxico de uma substância ou de formulações mais complexas. / The skin is the largest organ from the human body and constitutes the main protection of the organism against physical and chemical agents and it is also fundamental to avoid water loss by desiccation. Formed by three distinct stratus, yet complementary, being the two main called dermis and epidermis, containing different cell types, as fibroblasts, keratinocytes, melanocytes, Merkel cells and Langerhans cells (LCs), being these latter fundamental in the contact hypersensitivity. Due to the importance of the healthy skin maintenance to the human´s life, there is a growing need of elaboration of skin models to the treatment of injured and diseased, as well as there is a big demand of skin models to chemical tests from the pharmaceutics and cosmetology fields. Another factor of fundamental importance to the development of alternative in vitro methods is the worldwide pressure for these tests to replace animal models. This approach meets new concepts of replacement, reduction and refinement in the use of animals in scientific studies, dictating the future of cell culture and bioengineering of skin models. Thanks to the large development of cell culture and the discovery that the cultured cells can be regrouped according to the experimental delineation, the creation of skin models to in vitro studies is made possible, as for instance, tests of cytotoxicity and phototoxicity or evaluation of the initial phase from the allergic reaction and processes of skin sensitization. In this case, it is necessary the achievement of a large amount of immature Langerhans cells. The LCs are immature dendritic cells located in the epidermis and superficial epithelium that perform a central role in the skin immunity, acting as real sentinels able to collect contact antigens. Accordingly, were tested four different protocols for extraction and cryopreservation of these cells, and further analyzed its morphological and phenotypic features. We obtained no significant results in relation to the isolation, purity and CD1a positive expression in the Protocol 2. The Protocols 1A and 3 offered high levels of CD1a positively marked cells, showing the same expression levels. However, the Protocol 3 provided a bigger number of viable cells and a high purity yield, since it only uses the epidermis to obtain the single cell suspension, which places it as a model to be followed in subsequent experiments. The methods appointed here as the most promising, can be reproduced in conventional cell culture labs, contributing to increase the reproducibility and reliability of experimental results related to the LCs. In the same way, we evaluated the use of the human skin equivalents to the accomplishment of in vitro tests of cyto and phototoxicity, which can in fact reduce the use of animal models to the identification of single substances toxicity or even complex formulations.