Background: Exposure of skin to UVB radiation (290-320 nm) modulates the immune system, with most studies showing a suppression of Th1-driven immune responses. Investigations into the effects of UVB exposure on allergic respiratory responses have been limited. This study investigated the systemic effects of UVB on Th2-associated immune responses using two different murine models of allergic respiratory inflammation. The mechanism of immune regulation was also examined. Methods and Results: Two murine models of asthma were used: the papain model and the ovalbumin (OVA) model using papain and OVA, respectively, as the allergens. In the papain model, C57BL/6, histamine receptor-1 knockout (H1RKO) and histamine receptor-2 knockout (H2RKO) mice were exposed to a single 4 kJ/m2 dose of UVB (twice a minimal oedemal dose) on shaved dorsal skin three days prior to intranasal sensitisation with papain, a cysteine protease homologue of the house dust mite (Dermatophagoides pteronyssinus) allergen Der p 1. Sensitisation and boost each consisted of five daily intranasal doses of 1 µg papain whilst the challenge consisted of three daily intranasal doses of 100 µg papain. Asthmatic symptoms were assessed 24 h after the final challenge dose. H1RKO mice demonstrated enhanced papain-specific inflammatory responses in the lung-draining lymph nodes (LDLNs) whilst the responses of H2RKO mice closely mimicked those of C57BL/6 mice. UVB irradiation three days before sensitisation reduced in vitro papain-specific proliferation of LDLN cells from C57BL/6 and H1RKO mice but not H2RKO mice 24 h after challenge. The regulatory effect of UVB was transferred by adoptive transfer of 5 x 106 unfractionated LDLN cells from UVB-irradiated, papain-sensitised and -challenged C57BL/6 and H1RKO donor mice into naïve recipients of the corresponding strain that were ii subsequently sensitised and challenged with papain. Additionally, UVB exposure suppressed papain-induced IL-5 and IL-10 production in vitro by LDLN cells from H1RKO mice but not from C57BL/6 mice or H2RKO mice. The results of this study demonstrate systemic immunomodulation of responses to intranasally delivered antigen by UVB irradiation and the induction of regulatory cells in the LDLN following UVB exposure. Furthermore, these results implicate a role for the H2R in UVB-induced suppression of antigen-specific responses in the draining lymph nodes.

A hanseníase é uma doença crônica causada por Mycobacterium leprae e apresenta diversas formas clínicas. O entendimento da interação parasita-hospedeiro na hanseníase evidenciou que ocorre a persistência assintomática do patógeno, caracterizando um estado de latência. Os fatores mais importantes relacionados com a permanência do patógeno são: a patogenicidade do agente infeccioso e o perfil da resposta imune, no qual os eventos de migração celular, produção de citocinas, as células efetoras e reguladoras são extremamente relevantes. As células T reguladoras (Treg) desempenham papel central na regulação da resposta imune em infecções crônicas o que favorece a persistência do patógeno. A importância de células T reguladores na hanseníase ainda é pouco conhecida. Neste trabalho investigou-se a presença de células T reguladoras em lesões e sangue periférico de indivíduos com hanseníase. Inicialmente avaliou-se a proliferação e a produção de citocinas por células mononucleares do sangue periférico (PBMC) de pacientes com hanseníase. Os resultados evidenciaram que não há diferenças quanto à proliferação de células T e produção de IFN-γ e TNF-α por células desses pacientes, mas a produção de IL-4 e IL-5 foi detectada apenas entre os pacientes com hanseníase virchoviana. Em relação à presença de células T reguladoras, os resultados evidenciaram aumento no número de linfócitos T CD4+CD25+FoxP3+ no sangue periférico de pacientes com hanseníase virchoviana. As células T reguladoras dos pacientes com hanseníase apresentaram elevada expressão de moléculas co-inibitórias PD-1, CTLA-4, GITR e ICOS. De modo relevante, as células T CD4+CD25+ isolados de pacientes com hanseníase virchoviana apresentaram maior atividade supressora quando comparado às células isoladas de pacientes com hanseníase tuberculóide. As células T CD4+CD25+ de pacientes com hanseníase virchoviana inibiram a proliferação de PBMC alogênico e a produção de IFN-γ e TNF-α. Os resultados demonstraram também que nas amostras de lesão de pele de pacientes com hanseníase virchoviana há acúmulo de células CD25+ produtoras de IL-10 e TGF-β, enquanto que estas células não foram detectadas nas lesões de pacientes com hanseníase tuberculóide. Dessa forma, os resultados descritos indicam que pacientes com hanseníase virchoviana apresentam aumento no número de células T reguladoras circulantes e no infiltrado inflamatório, e estas células apresentaram maior atividade supressora. O acúmulo de células T reguladoras no sítio da infecção pode ser correlacionado com o controle da resposta imune e conseqüente persistência de M. leprae. / Leprosy is caused by Mycobacterium leprae and its clinical features depend on the host immune background. The understanding of parasite-host interactions in leprosy have highlighted asymptomatic persistence of the pathogen, which indicates that this infection becomes latent. The most important factors related to the permanence of pathogens are: the pathogenicity of the infectious agents; the profile of the immune response developed by the host whose events of cellular migration, cytokines production, and the effector and regulatory cells are extremely relevant. The regulatory T cells (Treg) seem to play a central role in the regulation of the immune response in chronic infections, which favors the persistence of the pathogen. Herein, we analyzed the relation between tuberculoid and lepromatous leprosy with the presence and function of T regulatory cells from peripheral blood mononuclear cells (PBMC) and skin lesions from these patients. First, the proliferation and cytokine production of PBMC isolated from leprosy patients were analyzed. We did not observe any difference in the proliferation ability or IFN-γ and TNF-α release; however, the production of IL-4 and IL-5 was detected only in patients with lepromatous leprosy. Furthermore, T CD4+CD25+FoxP3+ cells were detected in the PBMC of patients with leprosy and these cells from lepromatous patients showed high expression of co-inhibitory molecules such as PD-1, GITR, CTLA-4 and ICOS. T CD4+CD25+cells isolated from patients with lepromatous leprosy were significantly more suppressive than the cells obtained from tuberculoid patients. In addition, TCD4+CD25+ cells isolated from patients with lepromatous leprosy inhibited allogeneic PBMC proliferation and their production of IFN-γ and TNF-α. The results also demonstrated that IL- 10 and TGF-ß were co-expressed with CD25+ cells at the inflammatory infiltrate of skin lesions from lepromatous patients, but similar results were not detected among tuberculoid patients. Thus, these results indicate that lepromatous leprosy patients have an enhanced presence of Treg cells with a suppressive ability in the blood and in the inflammatory infiltrate. The accumulation of Treg cells at the infection sites might be associated to the control of immune response and consequently to Mycobacterium leprae presistence.

Stress, either physical or psychological, can have a dramatic impact on our immune system. There has been little progress, however, in understanding chronic stress-induced immunosuppression. Naive CD4+ T cells could modulate immune responses via differentiation to T helper (Th) cells. In this study, we showed that stress promotes the release of the Th1 cytokines interferon (IFN)-γ and tumor necrosis factor (TNF)-α, the Th2 cytokines interleukin (IL)-4 and IL-10 and the Th17 cytokine IL-17 of splenic naive CD4+ T cells. This suggests that stress promotes the differentiation of naive CD4+ T cells to Th1, Th2 and Th17 cells. Knockout strategies verified that TLR2 might modulate the differentiation of Th1/Th2 cells by inhibiting p38 mitogen-activated protein kinase (MAPK). Taken together, our data suggest that chronic stress induces immune suppression by targeting TLR2 and p38 MAPK in naive CD4+ T cells.

No description available.

No description available.

Malariapigment Hemozoin wird üblicherweise als nicht-toxische, hochmolekulare, parasitäre Speicherform des nicht abgebauten, toxischen Häms aus dem Wirtszell-Hämoglobins betrachtet. Unaufgereinigtes Pigment, wie wir es im infizierten Erythroyzten finden und wie es nach Schizontenruptur freigesetzt wird, kann man als die "natürliche Diät" bezeichnen, die Makrophagen in Malaria-infizierten Wirten aufnehmen. Nach Aufnahme in den Makrophagen persistiert Hemozoin in den Lysosomen und wird nicht abgebaut. Das Häm-abbauende Enzym, die Häm-Oxygenase wird nicht induziert. Hemozoin ist eine potente Quelle für Radikale, woraus Lipoperoxide und davon abgeleitete Hydroxyaldehyde,wie 4-Hydroxynonenal resultieren . 4- Hydroxynonenal in Konzentrationen, wie sie in Hemozoin-beladenen Monozyten nachgewiesen wurden, hemmen die Proteinkinase C. In immunopräzipitierter Proteinkinase C aus Hemozoin- haltigen Makrophagen wurden ProteinkinaseC-Hydroxynonenal-Komplexe nachgewiesen. Die Hydroxynonenal-bedingte Hemmung der Proteinkinase C (und anderer bisher nicht untersuchter Enzyme und Prozesse) könnte die Hemozoineffekte auf den oxydativen burst und die Phagozytose erklären. Der Phorbolester-induzierte oxydative burst ist irreversibel gehemmt in Monozyten, die entweder Hemozoin oder aber Hemozoin-haltige infizierte Erythrozyten phagozytiert haben. Die Hemmung der NADPH-Oxydase, das für den oxydativen burst verantwortliche Enzym, durch intrazelluläres Hemozoin, sollte beträchtlich zur burst -Hemmung beitragen. Monozyten phagozytieren Hemozoin-haltige, infizierte Erythrozyten oder isoliertes Hemozoin , sind danach jedoch unfähig, erneut zu phagozytieren, wie es Monozyten nach Phagozytose und Verdau von nicht-infizierten Erythrozyten physiologischerweise tun. Schließlich ist die Expression von Membranantigenen, die für die Immunantwort von Bedeutung sind, in Hemozoin-haltigen Monozyten vermindert. Die Induktion des für die Präsentation externer Antigene verantwortlichen Histokompatibilitätskoplexes (MHC) Klasse II durch Interferon-gamma ist in Hemozoin-beladenen Monozyten aufgehoben. Sowohl das Interzelluläre Adhäsionsprotein 1 (CD54) als auch p150,95 Integrin (CD11c) sind in Hemozoin-haltigen Monozyten vermindert Oberflächen-exprimiert. Trotz der verschiedenen funktionellen Einschränkungen sind Hemozoin-beladene Phagozyten vital. Bei Plasmodium-falciparum-Malaria enthält ein hoher Anteil von Gewebsmakrophagen und zirkulierender Monozyten und Leukozyten große Mengen an Hemozoin. Wichtige Funktionen wie oxydativer burst , Phagozytose und die Expression von MHC Klasse II sind in Hemozoin- beladenen Phagozyten gestört. Es scheint deshalb gerechtfertigt, die Hemozoin-Beladung als wichtigen Faktor in der gestörten Immunantwort bei der P.falciparum-Malaria zu betrachten. / Malaria pigment hemozoin is generally considered to be a non-toxic, high-molecular-weight, parasitic storage form of undigested,toxic, host-hemoglobin-heme.Crude pigment, as present in infected erythrocytes and shed after schizont rupture, may be considered the 'natural diet' ingested by macrophages in malaria-infected hosts. After ingestion by macrophages hemozoin persists in the lysosomes without being degraded. The heme-degrading enzyme, the heme-oxygenase, is not induced. Hemozoin is a powerfull source of radicals that generates lipoperoxides and derived, toxic hydroxyaldehydes such as 4-hydroxynonenal. High concentrations of 4-hydroxynonenal, which have been detected in hemozoin-fed macrophages, inhibit protein kinase C. Complexes between hydroxynonenal and protein kinase C have been detected in immunoprecipitated protein kinase C from hemozoin-fed macrophages. Hydroxynonenal-mediated inhibition of protein kinase C (and of other as yet unidentified enzymes and processes) may explain hemozoin-mediated effects on oxidative burst and phagocytosis. The phorbol ester-eliceted oxidative burst is irreversibly suppressed in monocytes fed with hemozoin or hemozoin-containing, infected erythrocytes. The inhibition of NADPH-oxidase, the enzyme responsible for oxidative burst, by ingested hemozoin should considerably contribute to burst inhibition. Monocytes avidly ingest infected hemozoin-containing erythrocytes or isolated hemozoin but are unable to repeat the phagocytic cycle as monocytes do after phagocytosis and digestion of non-infected erythrocytes. Finally , the expression of membrane antigens involved in the immune response is decreased in hemozoin-loaded monocytes. The induction of the major histocompatibility complex (MHC) class II by interferon-gamma, that is responsible for presentation of external antigens, is abrogated in hemozoin-loaded monocyte. The intercellular adhesion molecule 1 (CD54) as well as the p150,95 integrin (CD11c) are decreased on the surface of monocytes containing hemozoin. Despite multiple functional impairments, hemozoin-loaded phagocytes remain alive. In Plasmodium-falciparum malaria large portions of resident macrophages and circulating monocytes and leukocytes contain massive amounts of hemozoin. Important functions like oxidative burst, phagocytosis and the expression of MHC class II are severely impaired in hemozoin-fed phagocytes. It seems therefore likly that hemozoin loading may play an important role in the impairment of the immune response seen in P.falciparum malaria.

Antibodies passively administered together with their specific antigen can enhance or suppress the specific antibody response. This phenomenon is known as antibody feedback regulation. Whether this modulation causes up- or downregulation of the antibody response depends both on the antibody isotype and the antigen used. IgG antibodies passively administered together with particulate antigens, e.g. erythrocytes, can completely prevent the induction of an antibody response to the antigen. The suppressive capacity of IgG has been routinely used in the clinic since the 1960’s in RhD-prophylaxis to prevent hemolytic disease of the fetus and newborn. Although studied for decades, the underlying mechanism of IgG-suppression has remained elusive. The main focus of this thesis has been to elucidate the mechanism behind IgG-suppression of antibody responses in vivo in mouse models using intravenous immunization with specific IgG together with native or haptenated sheep red blood cells, SRBC. We show that IgG-suppression of IgM and long-term serum IgG-responses operates independently of activating FcγRI, III, IV, or the inhibitory FcγRIIB, thus confirming and extending previous findings. Moreover, we demonstrate for the first time that C1q, C3 and CR1/2 are dispensable for IgG-suppression of antibody responses. These findings strongly argue against the involvement of Fc-dependent mechanisms as the explanation for IgG-suppression. Interestingly, GC formation occurs in IgG-suppressed mice although the antibody response to surface SRBC epitopes are completely suppressed. The data suggests that these GCs develop in response to intracellular SRBC epitopes as well as to the passively administered suppressive IgG. Moreover, we demonstrate that passively administered IgG suppresses several parameters of an antibody/B cell response including antigen specific GC and non-GC B cells, extra-follicular antibody secreting cells, long-lived plasma cells and induction of immunological memory. Before the onset of the present study, two mechanisms appeared compatible with the majority of experimental findings: IgG-mediated antigen clearance and epitope masking. Herein we show that the contribution of IgG-mediated antigen clearance is negligible and that suppression of IgG-responses is strictly epitope specific. This provides compelling evidence that a very important mechanism underlying IgG-suppression is epitope masking.

Influenza virus infects the human population worldwide and causes acute respiratory disease. Currently, the primary strategy for preventing influenza is seasonal vaccination which is capable of providing protection in most populations. However, seasonal vaccines are less efficacious to immunize the elderly and poorly induce cross-protective immunity against the reassorted pandemic virus in the recipients. Neuraminidase (NA) inhibitors have also been widely utilized to limit disease outcome. The currently used NA inhibitors, nonetheless, generate the drug-resistant progeny viruses; moreover, they are unable to directly target the host immune responses which cause immunopathology in severe cases. Therefore, new strategies that provide more effective immunogenicity, cross-protection and therapies against influenza infection must be developed. In this thesis, the adjuvanticity of CpG oligodeoxynucleotide (ODN), type I interferon (IFN) and Complete Freund’s adjuvant (CFA) when coadministered with seasonal influenza vaccines in ferrets is presented. It has been found that the adjuvanted vaccines are efficacious to induce neutralizing antibody responses. Several common and distinguished signaling pathways leading to dendritic cell (DC) maturation and B cell activation have been discovered from their adjuvanticity. Furthermore, it was determined that seasonal H1N1 prior infection more effectively induces cross-protection against the newly emerged 2009 pandemic H1N1 (H1N1pdm) virus in ferrets and mice than the seasonal vaccines. The prior infection-induced cross-reactive but non-neutralizing antibodies are capable of providing substantial protection in the H1N1pdm infected mice when CD8 T cells are absent. Lastly, function of different vaccine adjuvants for controlling H1N1pdm infection in mice has been investigated. Unlike other adjuvants, CFA is capable of protecting the mice from infection through enhancement of Treg cell suppressive molecules galectin-1 and CTLA-4 which downregulated DC costimulation and effector T cell responses. Overall, this thesis has provided novel mechanistic insights for developing protective strategies against influenza infection.

Influenza virus infects the human population worldwide and causes acute respiratory disease. Currently, the primary strategy for preventing influenza is seasonal vaccination which is capable of providing protection in most populations. However, seasonal vaccines are less efficacious to immunize the elderly and poorly induce cross-protective immunity against the reassorted pandemic virus in the recipients. Neuraminidase (NA) inhibitors have also been widely utilized to limit disease outcome. The currently used NA inhibitors, nonetheless, generate the drug-resistant progeny viruses; moreover, they are unable to directly target the host immune responses which cause immunopathology in severe cases. Therefore, new strategies that provide more effective immunogenicity, cross-protection and therapies against influenza infection must be developed. In this thesis, the adjuvanticity of CpG oligodeoxynucleotide (ODN), type I interferon (IFN) and Complete Freund’s adjuvant (CFA) when coadministered with seasonal influenza vaccines in ferrets is presented. It has been found that the adjuvanted vaccines are efficacious to induce neutralizing antibody responses. Several common and distinguished signaling pathways leading to dendritic cell (DC) maturation and B cell activation have been discovered from their adjuvanticity. Furthermore, it was determined that seasonal H1N1 prior infection more effectively induces cross-protection against the newly emerged 2009 pandemic H1N1 (H1N1pdm) virus in ferrets and mice than the seasonal vaccines. The prior infection-induced cross-reactive but non-neutralizing antibodies are capable of providing substantial protection in the H1N1pdm infected mice when CD8 T cells are absent. Lastly, function of different vaccine adjuvants for controlling H1N1pdm infection in mice has been investigated. Unlike other adjuvants, CFA is capable of protecting the mice from infection through enhancement of Treg cell suppressive molecules galectin-1 and CTLA-4 which downregulated DC costimulation and effector T cell responses. Overall, this thesis has provided novel mechanistic insights for developing protective strategies against influenza infection.

Prolonged and intense exercise is known to modulate and suppress certain aspects of the immunoendocrine system. Such effects are thought to be largely mediated by the release of stress hormones and regulatory cytokines which originate from a variety of stress related paradigms in sport. These include acute physical exertion, chronic and repetitive exercise as well as other psychological and psychosocial aspects of training and competing in an elite environment. It may be of particular interest to study the effects of regular competition and training on immunoendocrine markers in rugby union players. At the professional level, rugby is an intense and physically demanding game where a significant amount of tissue trauma occurs as a result of the many game collisions. The aims of the studies outlined in this thesis were to determine the effects of acute, repeated and chronic exercise exposure on immunoendocrine markers and illness incidence in professional rugby union. Additional case studies were also undertaken to supplement main study findings. The first part of the thesis documented the effects of acute and repeated exercise on immunoendocrine markers in a cohort of international rugby union players. Data in study 1 showed that large disturbances in immunoendocine and hormone levels occur in players (n = 10) following game play. The magnitude of this response appeared dependent on game physicality (number of rucks/mauls, tackles) and the number of collisions players received during match play. Findings also showed suppression in host immunity, and in particular, innate immune function (neutrophil degranulation) which was not resolved 38 h (-29%) into the recovery period. In study 2, bloods were taken from players (n = 8) across a 21-day international rugby series. Data revealed that players entered the international camp with residual muscle damage (creatine kinase; CK) and inflammation (hs-CRP) following previous club involvement in European cup rugby. Further increases in stress related markers (cortisol, IL-6, CK, CRP) were not evident throughout the players time at the international training base. Conversely, a progressive increase in anabolic-catabolic balance (T/C ratio) was observed across time. In comparison to values on camp-entry (day 1), increases in T/C ratio were evident on day-5 (9.8%), day-7 (13%), day-19 (35%) and day-21 (45%) (P < 0.05). This data is suggestive of improved physiological recovery and was commensurate with team fitness goals (reduced volume + maintenance of training intensity) for that time. Findings suggest that monitoring of player club activities and training load preceding international duty is pertinent if they are required to represent their country inside 7 days. The second part of the thesis evaluated the stress induced effects of chronic rugby exposure in professional club players. Questionnaire data analysed from study 3 showed that players (n = 65) perceived current season length as being ‘too long’ (55%), ‘poorly structured’ (56%) and that game demands are increasing with time (52%). Furthermore, the majority of players (80%) felt that time ‘away’ from rugby was not sufficiently long enough and were in favour of a mid-season break (2 wks in duration). Investigation into the effects of chronic exercise on illness incidence, immunological and psychological state was carried out in a squad of club players (n = 30) over a competitive season (n = 48 wks) in studies 4-6. Findings revealed that specific periods in a rugby season resulted in disturbances to hormonal and immune status. These periods occurred following breaks in club game fixtures [November international and Six-nations period: February/early March], times of increased training intensity and increased ratio of conditioning/rugby activity. Peaks in number of upper respiratory illnesses (URIs) and disturbances in psychometric variables also occurred during these time periods. In 23% of all URIs, players reported that the presence of the illness either reduced activity (14.4%) or felt the need to go to bed (8.6%). Positional differences in variables were also observed. A higher incidence of URIs (3.4 vs 4.3) and lower concentrations of resting immune markers [salivary lysozyme: s-Lys (-31%); immunoglobulin A: s-IgA (-27%)] was observed in ‘backs’ (vs forwards) over the season. Higher mid-season cortisol levels was also observed in backs (P < 0.05) while conversely, greater concentrations of plasma CK and CRP were found in forwards throughout the season. These findings indicate positional specific differences in response to exercise load and point to the role of group specific recovery at certain times during the season. Data from study 6 showed that the number of training related complaints decreased across the season, findings which closely resembled corresponding decreases in plasma CRP values. This data is suggestive of a ‘repeated-bout’ effect or ‘contact adaptation’ in rugby union. Finally, comparison of methods used in the recording of illness data revealed that players were more honest when disclosing the existence of banal infections to a web-based training diary and under-reported infections to medical staff.