In this study we show, to our knowledge, the first description of the role ADAM10 plays on mast cells. ADAM10 is abundantly expressed on mast cells both in vitro and in vivo. Its expression is inhibited by IL-10, a suppressive cytokine. siRNA depletion of ADAM10 on bone marrow-derived mast cells (BMMC) caused decreased IL-6 production following IgE cross-linking and also impaired BMMC stem cell factor (SCF)-induced migration through collagen IV. Mast cells and T helper cells (Th cells) in the peritoneum were reduced in ADAM10 KO mice. In addition, ADAM10 KO BMMC produced significantly less of all cytokines measured following IgE cross-linking, including IL-6, TNF-α, IL-13, and MCP-1, compared to wild type BMMC. Collectively these data show that mast cell ADAM10 can be regulated by a T regulatory cell cytokine, IL-10, and describes key ways in which ADAM10 loss affects prototypical mast cell functions and distribution.

Macrophages (MФ) and mast cells are important cell types in the context of tissue remodeling and regeneration. Mast cells participate in the early stages of wound healing and modulate the acute inflammatory responses to biomaterials. Mast cells can secrete a myriad of different cytokines by the process of degranulation; the process of regulated secretion in which preformed contents stored in their granules are rapidly released by exocytosis. Some of these cytokines such as IL-4, IL-13 and TNF-α can modulate the MФ phenotype. Macrophages (MΦ) are innate immune cells, crucial for tissue homeostasis, presentation of foreign and self-antigens following infection/injury, pathogen clearance, inflammation resolution, angiogenesis, and wound healing. MΦ display plasticity and can acquire pro-inflammatory (M1) or angiogenic/wound healing (M2) phenotypes depending upon the environmental stimuli. The phenotypic profile of MФ as M1 or M2 following exposure to the biomaterial can dictate the downstream processes of tissue remodeling and angiogenesis. An analysis of how these two cell types interact with electrospun biomaterials and how different properties of an electrospun biomaterial impacts the MΦ phenotype is the focus of this thesis. Mast cells synthesize several potent angiogenic factors and can also stimulate fibroblasts, endothelial cells and macrophages. An understanding of how they participate in wound healing and angiogenesis is important to further our knowledge about in situ vascular prosthetic regeneration. The adhesion, proliferation and cytokine secretion of bone marrow derived murine mast cells (BMMC) on electrospun polydioxanone (PDO), polycaprolactone (PCL) and silk scaffolds, as well as tissue culture plastic (TCP) has been investigated in the presence or absence of IL-3, SCF, IgE and IgE with a crosslinking antigen, dinitrophenol-conjugated albumin (DNP). It was previously believed that only activated BMMCs exhibit adhesion and cytokine secretion. However, this study shows non-activated BMMC adhesion to electrospun scaffolds. Silk scaffold was not found to be conducive for mast cell adhesion and cytokine secretion. Activation by IgE and DNP significantly enhanced mast cell adhesion, proliferation, migration and secretion of TNF-α, MIP-1α and IL-13. This indicates that mast cells might play a role in MФ polarization (M1/M2), biomaterial integration into the host tissue, regeneration, and possibly angiogenesis. In the next study, bone marrow derived murine macrophages (BMMΦs, 106 cells) were seeded on TCP (24 well plate) and PDO scaffolds (15 mm discs) electrospun from varying polymer concentrations (60, 100, and 140 mg/ml). Scaffold evaluation showed that large polymer concentrations led to larger fiber diameters, which in turn led to larger pore-sizes and porosity but a smaller surface area to volume ratio. After 24 hrs of culture, the cell lysates were analyzed for Arginase (Arg1) and inducible nitric oxide synthase (iNOS) expression by western blot and cell culture supernatants were analyzed for Nitric oxide (NO2-), Tumor Necrosis Factor – alpha (TNF-α), Interleukin-6 (IL-6), Vascular Endothelial Growth Factor (VEGF), Transforming Growth Factor – beta1 (TGF-β1) and basic fibroblast growth factor (bFGF) levels. The results indicated a correlation between Arg1 expression and increasing fiber/pore-size, indicating that the larger fiber/pore-sizes polarize towards a M2 phenotype. Also, the expression of iNOS was downregulated on the larger fiber/pore-size. The levels of NO2- were significantly higher on the lower fiber/pore-sizes indicating an M1 phenotype. The levels of VEGF, TGF-β1 and bFGF increased with increasing fiber/pore-sizes. The results showed higher Arg1 expression in M2s on the 60 mg/ml scaffold created by the air-flow impedance method compared to the 60 mg/ml scaffold created on the solid mandrel created by traditional electrospinning. The Arg1 expression was reduced on the compressed 140 mg/ml PDO scaffold compared to the normal 140 mg/ml scaffold. This result indicates that pore-size might be playing a greater role compared to fiber diameter in BMMФ phenotype modulation. In order to assess the angiogenic potential of BMMΦs cultured on PDO scaffolds, a 3D angiogenesis bead assay was performed using conditioned media from the BMMΦ:PDO interaction. The results of the 3D angiogenesis bead assay showed that the conditioned media from BMMΦs of M0 and M2 phenotypes cultured on the 140 mg/ml PDO scaffold induced larger sprouting and higher percentage density of sprouts when compared to the 60 mg/ml PDO scaffold and TCP. To investigate the signaling mechanism involved in this phenotypic switch, BMMΦs were isolated from the bone marrow of MyD88 knockout (KO) mice (Jackson Laboratories) and cultured on PDO (60 and 140 mg/ml) scaffolds (106 /disc) and TCP for 24 hrs and their Arg1 and iNOS expression was analyzed by western blot. The expression of Arg1 and iNOS was severely impaired on the BMMΦs from MyD88-/- mice cultured on the 140 mg/ml scaffold when compared to the 60 mg/ml PDO scaffold and TCP. This result indicates that scaffolds with different fiber/pore-sizes signal differently. A subcutaneous mouse model (described in Chapter 6) was used to evaluate the angiogenic and regenerative potential of PDO scaffolds in vivo. The DIVAA assay showed statistically higher FITC-dextran signal intensity for the 140 mg/ml scaffold compared to the 60 mg/ml scaffold indicating greater angiogenic response in the 140 mg/ml tube. However, problems of high background were observed in this assay with the use of electrospun PDO. The observed high background was probably due to the formation of complexes between dextran and adsorbed plasma proteins on the surface of the PDO. More studies are needed to optimize this assay for use with biomaterials such as PDO. H&E staining of the harvested PDO tubes (60 mg/ml and 140 mg/ml) was also performed. The cross-sections of these tubes showed greater cell recruitment and infiltration into the fibrous structures of the 140 mg/ml tube compared to the 60 mg/ml tube. This result corroborates the in vitro result of BMMФ infiltrating deeper into the structures of the 140 mg/ml scaffold compared to the 60 mg/ml scaffold. The scaffolds were also analyzed by immunostaining for iNOS (indicative of M1 phenotype of MФs). The results showed statistically higher ratios of iNOS positive:negative areas on the 60 mg/ml scaffold compared to the 140 mg/ml scaffold. Overall, these studies indicate that 140 mg/ml scaffold supports greater cell recruitment and cell infiltration in vivo but a smaller ratio of iNOS positive:negative areas compared to the 60 mg/ml scaffold, which supports a predominately M1 MФ phenotype. The studies indicate that varying properties of PDO can alter both the phenotype and function of BMMΦs in vitro and in vivo. We have also shown that the 140 mg/ml scaffold signal BMMΦs through MyD88-dependent mechanisms. A complete understanding of the way materials signal would allow us to control or modulate undesirable immune reactions to biomaterials in vivo. These studies would also help engineer biomaterials that promote angiogenesis and regeneration.

Mast cells respond to a variety of signals, are associated with both increased inflammation and regulation of the immune response, and are able to interact with a variety of hematopoietic and non-hematopoietic cells. The majority of the work that highlights mast cell pleiotropic abilities has been completed in murine models. Though these models have significantly advanced our understanding of what mast cells can do, they cannot inform us as to what mast cells actually do in human beings. The goal of this dissertation is to assess fully mature, primary human mast cell function beyond the well-defined type 1 hypersensitivity function and place mature human mast cells in the context of interactions with other immune cells. The first project addresses the ability of IFNγ, a historically Th1 associated cytokine, to dramatically alter mast cell phenotype. In particular, IFNγ stimulation allows mast cells to act as antigen presenting cells to CD4+ T cells. The second project describes and addresses the T cell suppressive function of myeloid derived suppressor cells in Mastocytosis, a disease of clonal mast cells.

As doenças periodontais afetam os tecidos de suporte dos dentes e são desencadeadas por microrganismos que possuem a capacidade de invadir os tecidos periodontais. A evolução desta doença é influenciada pela resposta inflamatória e imunológica do hospedeiro e envolve a participação de diversos tipos celulares. Atualmente, existem evidências de que os mastócitos, além de outras funções, possuem a capacidade de eliminar bactérias, através da fagocitose. Assim sendo, este estudo teve por objetivo avaliar a capacidade fagocítica dos mastócitos frente ao periodontopatógeno A. actinomycetemcomitans, além de comparar sua capacidade fagocítica com a dos macrófagos, considerados fagócitos profissionais. Para este fim, foram realizados ensaios fagocíticos in vitro utilizando mastócitos e macrófagos murinos, desafiados ora com A. actinomycetemcomitans ora com Escherichia coli, opsonizados ou não, sob diferentes proporções célula: bactérias. Após 1 hora de desafio, as células foram coradas com laranja de acridina e avaliadas qualitativamente utilizando-se microscópio de varredura confocal a laser e quantitativamente através do microscópio de fluorescência convencional. Nossos resultados demonstraram que os mastócitos murinos se mostraram eficientes quanto a sua capacidade fagocítica frente a A. actinomycetemcomitans. Os valores percentuais de mastócitos com A. actinomycetemcomitans internalizados, na ausência de opsonização com complemento, foram maiores que aqueles na presença da opsonização, sugerindo a participação de receptores opsoninas-independentes no reconhecimento deste patógeno pelos mastócitos, além do receptor de complemento tipo 3 (CR3). Comparando os dois tipos celulares, verificou-se que ambas as células apresentaram importante atividade fagocítica contra A. actinomycetemcomitans, porém os valores percentuais de mastócitos com bactérias internalizadas sem complemento foram maiores que aqueles de macrófagos com bactérias internalizadas com complemento, em uma das proporções (1:10). Os resultados deste trabalho sugerem o papel dos mastócitos como fagócitos profissionais na patogênese da doença periodontal induzida por placa dentobacteriana. / Periodontal diseases affect the supporting tissues of the teeth and are triggered by microorganisms which are capable of invading periodontal tissues. The evolution of this disease is influenced by inflammatory and immune response of the host and involves the participation of different cell types. Currently, there is evidence that mast cells, among other functions, have the ability to eliminate bacteria by phagocytosis. Thus, this study aimed to evaluate the phagocytic ability of mast cells against the periodontopathogens A. actinomycetemcomitans, and compare with the phagocytic capacity of macrophages, which are considered professional phagocytes. Therefore, in vitro phagocytic assays were conducted using murine mast cells and macrophages, challenged with A. actinomycetemcomitans or Escherichia coli, at the same time, opsonized or not, under different proportions cell: bacteria. After 1 hour of challenge, cells were stained with acridine orange and qualitatively assessed by using a confocal laser scanning electron microscope and quantitatively by the conventional scanning fluorescence microscope. The results demonstrated that phagocytic ability of murine mast cells was effective against A. actinomycetemcomitans. The percentages of mast cells with A. actinomycetemcomitans internalized in the absence of opsonization with complement, were higher than those in the presence of opsonization, suggesting the involvement of opsonin-independent receptors in recognition of this pathogen by mast cells, as well as complement receptor type 3 (CR3). Comparing the two cell types, it was observed that both cells showed significant phagocytic activity against A. actinomycetemcomitans, however, the percentages of mast cells with internalized bacteria without complement were higher than those of macrophages with internalized bacteria with complement, in one of the proportions (1:10). The results suggest the role of mast cells as professional phagocytes in the pathogenesis of periodontal disease induced by dental plaque.

by Chung Lap Chan. / "March 1999." / Thesis (Ph.D.)--Chinese University of Hong kong, 1999. / Includes bibliographical references (p. 270-307). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Made available in DSpace on 2014-06-11T19:30:59Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-06-06Bitstream added on 2014-06-13T20:01:17Z : No. of bitstreams: 1 araujo_ac_dr_botib_parcial.pdf: 268121 bytes, checksum: edd3cb8f63dfdeca1bdff45c6a285127 (MD5) Bitstreams deleted on 2015-06-25T13:00:45Z: araujo_ac_dr_botib_parcial.pdf,. Added 1 bitstream(s) on 2015-06-25T13:03:12Z : No. of bitstreams: 1 000716406_20160731.pdf: 207684 bytes, checksum: 3b5f8364b84761be0ff6e1a7cadcc796 (MD5) Bitstreams deleted on 2016-08-01T11:30:02Z: 000716406_20160731.pdf,. Added 1 bitstream(s) on 2016-08-01T11:30:58Z : No. of bitstreams: 1 000716406.pdf: 1009644 bytes, checksum: 9956487a11a013c64929e4fac5497961 (MD5) / As reações alérgicas afetam grande parte da população e tem aumentado nos últimos anos. Nesse sentido, a histamina liberada pelos mastócitos é um mediador importante e a procura por compostos que inibam a liberação do referido mediador se faz necessária tendo em vista que os tratamentos disponíveis apresentam limitações. Estudos prévios demonstraram que o extrato metanólico bruto da casca do caule de Hymenaea stigonocarpa (ME) apresenta atividade inibitória sobre a liberação de histamina. Assim, o presente trabalho realizou o fracionamento biomonitorado do ME a fim de identificar a(s) frações mais ativa(s). As frações foram avaliadas em suspensão de mastócitos peritoneais de ratos Wistar machos desafiados com ionóforo A23187 e composto 48/80 (apenas as frações mais ativas). Posteriormente, a fração mais ativa foi avaliada em mastócitos sensibilizados com ovoalbumina (OVA). A dosagem de histamina foi realizada utilizando-se um sistema fluorimétrico automatizado e a análise fitoquímica por CG/EM. Os resultados mostraram que a fração acetato de etila foi a mais ativa e, na concentração de 100 g/mL inibiu em 78, 98 e 85% a liberação de histamina induzida pelo ionóforo A23187, composto 48/80 e OVA respectivamente. O fracionamento biomonitorado desta fração por cromatografia líquida sob vácuo (CLV) gerou seis sub-frações, das quais as mais ativas demonstraram ser constituídas por terpenos e ácidos graxos de cadeia longa / Allergic reactions affect most of the population and has increased in recent years. Accordingly, histamine released by mast cells is an important mediator and search for compounds that inhibit release of that mediator is necessary in order that the treatments available have limitations. Previous studies demonstrated that the crude methanol extract of the stem bark of Hymenaea stigonocarpa (ME) has an inhibitory activity on the histamine release. Thus, the present study performed the bioguided fractionation of the ME in order to identify (s) most active fractions (s). The fractions were evaluated on the histamine release from rat peritoneum mast cells challenged with ionophore A23187 and compound 48/80 (only the most active fractions). Subsequently, the most active fraction was evaluated in mast cells sensitized with ovalbumin (OVA). The dosage of histamine was performed using an automated fluorimetric system and phytochemical analysis by GC/MS. The results showed that the ethyl acetate fraction was the most active and at concentration of 100 g/mL inhibited by 78, 98 and 85% histamine release induced by ionophore A23187, compound 48/80 and OVA, respectively. The bioguided-fractionatation of this fraction by vacuum liquid chromatography (VLC) generated six sub-fractions, of which the most actives showed the presence of terpenes and long chain fatty acids

As doenças periodontais afetam os tecidos de suporte dos dentes e são desencadeadas por microrganismos que possuem a capacidade de invadir os tecidos periodontais. A evolução desta doença é influenciada pela resposta inflamatória e imunológica do hospedeiro e envolve a participação de diversos tipos celulares. Atualmente, existem evidências de que os mastócitos, além de outras funções, possuem a capacidade de eliminar bactérias, através da fagocitose. Assim sendo, este estudo teve por objetivo avaliar a capacidade fagocítica dos mastócitos frente ao periodontopatógeno A. actinomycetemcomitans, além de comparar sua capacidade fagocítica com a dos macrófagos, considerados fagócitos profissionais. Para este fim, foram realizados ensaios fagocíticos in vitro utilizando mastócitos e macrófagos murinos, desafiados ora com A. actinomycetemcomitans ora com Escherichia coli, opsonizados ou não, sob diferentes proporções célula: bactérias. Após 1 hora de desafio, as células foram coradas com laranja de acridina e avaliadas qualitativamente utilizando-se microscópio de varredura confocal a laser e quantitativamente através do microscópio de fluorescência convencional. Nossos resultados demonstraram que os mastócitos murinos se mostraram eficientes quanto a sua capacidade fagocítica frente a A. actinomycetemcomitans. Os valores percentuais de mastócitos com A. actinomycetemcomitans internalizados, na ausência de opsonização com complemento, foram maiores que aqueles na presença da opsonização, sugerindo a participação de receptores opsoninas-independentes no reconhecimento deste patógeno pelos mastócitos, além do receptor de complemento tipo 3 (CR3). Comparando os dois tipos celulares, verificou-se que ambas as células apresentaram importante atividade fagocítica contra A. actinomycetemcomitans, porém os valores percentuais de mastócitos com bactérias internalizadas sem complemento foram maiores que aqueles de macrófagos com bactérias internalizadas com complemento, em uma das proporções (1:10). Os resultados deste trabalho sugerem o papel dos mastócitos como fagócitos profissionais na patogênese da doença periodontal induzida por placa dentobacteriana. / Periodontal diseases affect the supporting tissues of the teeth and are triggered by microorganisms which are capable of invading periodontal tissues. The evolution of this disease is influenced by inflammatory and immune response of the host and involves the participation of different cell types. Currently, there is evidence that mast cells, among other functions, have the ability to eliminate bacteria by phagocytosis. Thus, this study aimed to evaluate the phagocytic ability of mast cells against the periodontopathogens A. actinomycetemcomitans, and compare with the phagocytic capacity of macrophages, which are considered professional phagocytes. Therefore, in vitro phagocytic assays were conducted using murine mast cells and macrophages, challenged with A. actinomycetemcomitans or Escherichia coli, at the same time, opsonized or not, under different proportions cell: bacteria. After 1 hour of challenge, cells were stained with acridine orange and qualitatively assessed by using a confocal laser scanning electron microscope and quantitatively by the conventional scanning fluorescence microscope. The results demonstrated that phagocytic ability of murine mast cells was effective against A. actinomycetemcomitans. The percentages of mast cells with A. actinomycetemcomitans internalized in the absence of opsonization with complement, were higher than those in the presence of opsonization, suggesting the involvement of opsonin-independent receptors in recognition of this pathogen by mast cells, as well as complement receptor type 3 (CR3). Comparing the two cell types, it was observed that both cells showed significant phagocytic activity against A. actinomycetemcomitans, however, the percentages of mast cells with internalized bacteria without complement were higher than those of macrophages with internalized bacteria with complement, in one of the proportions (1:10). The results suggest the role of mast cells as professional phagocytes in the pathogenesis of periodontal disease induced by dental plaque.

Orientador: Ana Lia Anbinder / Coorientadora: Noala Vicensoto Moreira Milhan / Banca: Fábio Luiz Coracin / Banca: Monica Ghislaine Oliveira Alves / Resumo: Granuloma piogênico (GP) é uma lesão de origem inflamatória que ocorre frequentemente em pele e cavidade oral. Existem dois subtipos histológicos: o tipo não lobular (GPNL), que é caracterizado por proliferação vascular semelhante a tecido de granulação, sem padrão de organização; e o tipo lobular (GPL) que se caracteriza pela organização dos vasos em agregados lobulares, separados por feixes de tecido conjuntivo. O objetivo deste estudo foi revisar todos os casos de granulomas piogênicos do nosso serviço de patologia bucal, a partir do ano 2000, reclassificar e correlacionar as características clínicas, microscópicas e imuno-histoquímicas com os subtipos da lesão. No levantamento foram encontrados no arquivo 197 casos diagnosticados como granuloma piogênico e hemangioma lobular capilar. Após revisão das lâminas, 9 casos foram reclassificados, e 19 foram excluídos, restando 169 casos, sendo 62 de GPL e 107 de GPNL. Foram coletados ainda dados como sexo, idade, local da lesão, tipo de nódulo, ocorrência de trauma prévio e hipótese diagnóstica clínica. Reações imuno-histoquímicas (GLUT-1, CD34, D2-40, AML e Mast cell) de 22 casos, sendo 11 lobulados e 11 não lobulados. A média de idade de acometimento foi de 38,59±16,96 anos, com 55,62% dos casos ocorrendo em pacientes do sexo feminino (10,12% durante gravidez), com maior acometimento em gengiva (39,64%), 44,97% dos nódulos eram do tipo pediculado e 13,02% relataram trauma mecânico prévio. O GPNL ocorre mais em gengiva, enquant... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Pyogenic granuloma (GP) is an inflammatory lesion that occurs frequently in the skin and oral cavity. There are two histological subtypes: the non-lobular type (NLCH), which is characterized by vascular proliferation similar to granulation tissue, without organization pattern; and lobular capillary hemangioma (LCH) characterized by the organization of vessels in lobular aggregates, separated by bundles of connective tissue. The purpose of this study was to review all cases of pyogenic granulomas of our oral pathology service, from the year 2000, to reclassify and correlate the clinical, microscopic and immunohistochemical characteristics with the subtypes of the lesion. In the survey, 197 cases diagnosed as pyogenic granuloma and lobular capillary hemangioma were found in our files. After review, 9 cases were reclassified, and 19 were excluded, remaining 169 cases, being 62 LCH and 107 NLCH. Data such as sex, age, site of lesion, type of nodule, previous trauma and clinical diagnostic hypothesis were also collected. Immunohistochemical reactions (GLUT-1, CD34, D2-40, SMA and Mast cell) of 24 cases, 11 LCH and 11 NLCH. Mean age was 38.59±16.96 years, with 55.62% of cases occurring in female patients (10.12% during pregnancy), with a greater involvement in gingiva (39.64%), 44.97% of the nodules were pedunculated and 13.02% reported previous mechanical trauma. The NLCH occurs more in gingiva, while LCH affects more lips (p<0,05). The number of microvessels (CD34 positive), SMA ... (Complete abstract click electronic access below) / Mestre

Mast cells (MCs) play a central role in inflammation by releasing mediators following activation. S100A8 and S100A9 are abundantly expressed in inflammatory sites such as asthmatic lung, sunburnt skin and atherosclerosis where MCs are involved in pathogenesis; roles of S100A8 in MC function are undetermined. The aims of this thesis were to determine effects of S100A8 on MC activation, particularly provoked by IgE and UVB. Initially, effects of UVB on MC activation were investigated as detailed functions were unclear. Cord blood-derived human mast cells (CBMCs) were treated in vitro with varying doses of UVB and production of multiple cytokines and viability investigated. UVB exposure selectively increased levels of IL-8 (CXCL8), and to a less extent IL-1β, but not eight other cytokines tested. New protein synthesis partially contributed and IL-8 production was p38 MAPK-dependent. UVB dose-dependently induced MC apoptosis indicating a potential regulatory mechanism of MC function. The ability of recombinant S100A8, S100A9 or S100A8/9 heterodimer to modulate IgE/antigen (DNP/anti-DNP)-mediated activation of a murine MC line, and of bone marrow-derived (mBM) MC activation was determined. The S100s did not directly induce degranulation or induce IL-6. S100A8 significantly inhibited DNP/anti-DNP-provoked degranulation, and IL-6 and TNF mRNA and protein induction. S100A8 did not alter FcεRIα expression. S100A9 was less effective; and the S100A8/9 complex was also suppressive. S100A8 only weakly suppressed non-specific MC degranulation. Mutation of Cys41 in S100A8 negated its suppressive activity. Because S100A8 scavenges oxidants via this reactive Cys residue, we propose that this may mediate its ability to downmodulate IgE-dependent MC responses. Similar to the thiol scavenger N-acetyl-L-cysteine, S100A8 but not the Ala41 mutant, attenuated DNP/anti-DNP-provoked LAT phosphorylation. However, the disulfide-bonded S100A8 dimer and S100A8 containing a sulfinamide bond between Cys41 and Lys34/35 also reduced MC activation, indicating an additional pathway(s). S100A8 did not suppress antigen/IgE-induced responses of CBMC possibly because these may not truly reflect fullymature human tissue MCs. S100A8 did not alter UVB-induced IL-8 release by CBMCs, or affect apoptosis. Murine S100A8 may have anti-inflammatory properties by regulating MC activation in an activator-specific manner, at least partially by scavenging ROS to suppress intracellular signalling.

<p>Mast cells (MCs) are forceful multifunctional effector cells of the immune system. MCs are normally distributed throughout connective and mucosal tissues, but in several pathological conditions accumulation of MCs occur. This accumulation is probable due to directed migration of MCs and they are subjects for migration at least two different occations: 1) when they are recruited as progenitor cells from the blood into the tissue; and 2) when they as mature MCs are recruited to sites of inflammation. The aim of this study was to investigate MC migration to chemoattractants released <i>in vivo</i> or <i>in vitro</i> (body fluids collected from patients with asthma or rheumatoid arthritis and T_H1- and T_H2-cytokines) and to recombinant cytokines (transforming growth factor -β (TGF-β) and CCL5/RANTES).</p><p>This thesis shows that bronchoalveolar lavage (BAL) fluid from asthmatic patients and synovial fluid from patients with rheumatiod arthritis contain MC chemoattractants, and that part of the chemotactic activity can be related to the presence of stem cell factor (SCF) and TGF-β. We also show that MC chemotactic activity during pollen season is significantly increased compared to before pollen season. Furthermore, we demonstrate that TGF-β isoforms, CCL5, TNF-α and IL-4 act as MC chemoattractants in a bellshaped dose- dependent manner. TGF-β proved to be an extremely potent attractant giving an optimal migratory response at 40fM and TGF-β3 being the most effective isoform. The chemokine CCL5 induced migration through interaction with the receptors CCR1 and CCR4 expressed on MC. Furthermore, we also found that TNF-α produced by T_H1-lymphocytes and IL-4 produced by T_H2-lymphocytes are MC chemoattractants.</p><p>In conclusion, with this thesis we have identified six new human mast cell chemoattractants and provide evidence that BAL fluid and synovial fluid from patients with asthma and rheumatoid arthritis, respectivly, contain MC chemoattractants. This information provides important clues in understanding the mechanisms behind MC recruitment to sites of inflammation.</p>