NKT cells are a population of T cells that have a broad range of regulatory effects on the immune system. Somewhat paradoxically, they can both suppress and potentiate cell-mediated immune responses; for example, while they can suppress some autoimmune diseases, they can also promote potent tumour rejection. There is accumulating evidence to suggest that this functional dichotomy can be explained by the existence of functionally distinct NKT cell subsets, which can differentially regulate the behaviour of other immune cells and drive remarkably different outcomes in disease settings. / Studies in vivo and in vitro have demonstrated remarkable functional diversity between NKT cell subsets of different phenotypes, and deriving from different tissues. This thesis examined functional differences between NKT cell subsets in the context of type 1 diabetes in NOD mice, identified a phenotypically and developmentally distinct IL-17 producing NKT cell subset, and investigated the functional effects of thymic NKT cells on the development and maintenance of conventional T cells and thymic stromal cells. The data presented in this thesis adds to the accumulating evidence that NKT cells are a functionally heterogeneous population, and reiterates the important point that subsets of NKT cells should be studied separately in order to properly understand the biological function of this important regulatory T cell population, and to maximise their clinical potential.

Semi-invariant natural killer T (iNKT) cells are critical components of the host immune response in peripheral tissues such as the lung, liver, and gut, and they play important roles in cancer, bacterial infections, autoimmunity, wound repair, and atherosclerosis. Tissue-resident iNKT cells exert their effects early in the developing immune response by rapidly producing a wide variety of cytokines and chemokines, and it was recently discovered that different tissues possess iNKT cell subsets that preferentially produce IFN-γ (NKT1), IL-4 (NKT2), or IL-17 (NKT17). Despite their critical role in the immune response, the mechanisms that regulate iNKT cell function in the periphery remain unclear. Signaling lymphocyte activation marker (SLAM) proteins are cell surface-expressed molecular switches that are expressed on all hematopoietic cells. The nine SLAM family receptors serve a variety of functions including promotion of cell-cell adhesion, regulation of cytokine production, co-stimulation, and inhibition. Importantly, SLAM family receptors are critical for the development of iNKT cells. Yet, numerous efforts to ascribe discrete roles of SLAM family receptors in iNKT cell function has proven difficult. We conducted a comprehensive analysis of SLAM family receptor co-expression on iNKT cell subsets in the lung, spleen, liver, and thymus and identified co-expression profiles that varied in a tissue and strain-dependent manner. Interestingly, we found that SLAM family receptor expression profiles varied among different iNKT cell subsets. In particular, we noted a close association of SLAMf6 expression with the NKT2 and NKT17 subsets in both the periphery and in the thymus. Further investigation using SLAMf6-deficient mice revealed a critical role for SLAMf6 in NKT2 and NKT17 subset development, and in iNKT IL-4 and IL-17 cytokine production in the periphery. This investigation also revealed that the SLAMf6high NKT2 and NKT17 subsets exhibited significantly higher proliferative capacity than the NKT1 subset and the NKT2 and NKT17 proliferation was dependent, in part, on SLAMf6 expression. Since Slam family genes are highly polymorphic, we next investigated whether these polymorphisms regulated iNKT function. We employed a B6.129 congenic mouse exhibiting impaired NKT cell function, in which a 6.6 Mbp 129/SvJ locus encompassing Slam genes was introgressed onto the C57BL/6 background. To test the hypothesis that Slam gene polymorphisms regulate iNKT cell function, we refined this genetic interval by generating B6.129 subcongenic lines and assessing iNKT cell function. Unexpectedly, we found that while Slam gene polymorphisms in this model do regulate iNKT cell function, the dominant regulator was in a 0.14 Mbp interval centromeric to the Slam genes. Further experimentation revealed that impaired iNKT cell development and function was associated with changes in the expression of Fcgr3 (Fc gamma receptor III) on iNKT cells, suggesting it as a novel candidate gene regulating iNKT cell function. Taken together, these data reveal for the first time a specific role for SLAMf6 on NKT2 and NKT17 subset development and function. In addition, these data identify Fcgr3 as a novel candidate gene that regulates iNKT cell subset development and cytokine production. Cumulatively, these data reveal the presence of discrete regulatory mechanisms at work in different iNKT subsets, a finding that has broad implications for our understanding of iNKT-cell mediated immunity.

Natural killer T (NKT) cells are a subset of T cells that modify a variety of immune responses. NKT cells recognize glycolipid antigen presented by a molecule called CD1d, a nonclassical antigen-presenting molecule. The best known subset of CD1d-dependent NKT cells expresses an invariant T cell receptor Vα (TCR-α) chain. These are referred to as type I or invariant NKT (iNKT) cells. When stimulated by a glycolipid, NKT cells rapidly release large amounts of cytokines. Cytokines released by NKT cells can induce either Th1 or Th2 responses. Th1 cytokines are effective in regulating bacterial, parasitic, and viral infections. But Th1 responses are also involved in some autoimmune diseases, such as type 1 diabetes, lupus, rheumatoid arthritis, and allergen-induced asthma. Th2 cytokines can attenuate proinflammatory Th1 responses and therefore prevent some autoimmune diseases. Lysosomal processing and CD1d loading is very important in regulating the stimulatory properties of antigens. Analogs of KRN7000, with small molecules appended on C6” position of the galactose portion, do not significantly change stimulation of NKT cells. The question is if the substitution at this position would influence the lysosomal processing. Two sets of mono- and disaccharides with and without substitution at C6” position were prepared and evaluated the NKT cell stimulatory properties. The substitution at the C6” position of the sugar moiety of glycolipids do not significantly impact the stimulatory properties of glycolipids and their processing in lysosome. Small changes at C6” are well tolerated. A double bond in the acyl chain and modification of the C6” functional group helped the glycolipid loading into CD1d and NKT cells stimulation. PBS57 is 100 times more active than KRN 7000 in stimulation of NKT cells responses in vitro and in vivo. This improvement is probably due to increasing solubility and improving binding ability with the CD1d.

No description available.

Introduction: NKT cells are categorised as borderline between NK and T cells, sharing phenotypic and functional characteristics of both cells, demonstrating their capacity to contritube to both pro- or anti-inflammatory processes. However, the role of these cells among lung transplant recipients remains largely unknown. The aim of this study was to determine the role of NKT cells following lung transplantation. Methods: NKT cells were quantified and characterised according to markers of: activation (CD107a, CD161, NKG2D) and immunomodulation (CD200 and CD200R) in peripheral blood and BALs. NKT cell numbers and phenotypes were correlated to clinical variables: immunosuppression, acute rejection, acute infections (viral, bacterial and fungal), bronchiolitis obliterans syndrome (BOS grade), lung function, and demographic variables. Interactions between NKT cells and the transplanted lung were linked by determining the relative expression of immunomodulatory ligand CD200 in lung biopsies. In vitro models were employed to determine the role of NKT cells to acute lung injury, either alone or in combination with cells of the mononuclear phagocyte system (MPS). Results: Higher numbers of immunomodulatory NKT cells (CD200+ and CD200R+) were found as lung function decreased. Data from peripheral blood indicates that recipients whose donors or themselves had been exposed to CMV infection demonstrated increased numbers of NKT cells. Patients with active EBV infections demonstrated higher NKT cell numbers expressing CD200 and CD200R. Data from BALs, indicates that patients with active fungal infections present higher immunomodulatory (CD200R) NKT cells and lower cytotoxicity marker (CD107a). In peripheral blood, lung recipients demonstrated higher NKT cell numbers compared to healthy volunteers. However, the lower relative mean expression of functional markers in the lung transplant group suggests that cells are less active. In vitro cultures with immunosuppressants demonstrated that cell cycle inhibitors (MMF and AZA) and corticosteroids (Prednisolone) are likely to inhibit NKT cell proliferation, while calcineurin inhibitors (Cyclosporine A and Tacrolimus) decrease the relative mean expression of activation markers. Clinical observations indicate that higher doses of Azathioprine may correlate with increased NKT cell numbers and the relative expression of CD200 and CD200R. However, under these conditions the relative expression of activation marker NKG2D decreases. In vitro data from the acute injury model indicates that NKT cells are capable to migrate into the injured lung and become activated following transmigration which is facilitated by the presence of monocytes. We also observed the interaction of NKT cells with endothelial cells, monocytes and macrophages. Also, the relative mean expression of CD200 and CD200R increased at the capillary layer, regardless of injury while upregulation of activation markers (CD107a, CD161 and NKG2D) was found at the capillary layer, following injury. In contrast, the alveolar layer demonstrated a decrease in both activation and immunomodulatory markers, following acute injury. Conclusions: Despite immunosuppression, NKT cells remain present in peripheral blood and BAL following lung transplantation. NKT cell proliferation is likely to be reduced by effect of cell cycle inhibitors, while calcineurin inhibitors exert an immunomodulatory effect. Our data indicates that NKT cells can participate in inflammatory and immunomodulatory events at the alveolar bilayer. Their capacity to infiltrate the lungs was assisted by cells of the mononuclear phagocyte system (MPS), which play an important role in antigen presentation and modulation of acute injury. Further research is needed to elucidate the signals and mechanisms occurring between NKT and MPS interactions and the outcomes these populations drive in acute lung injury.

No description available.

No description available.

The use of genome wide ENU mutagenesis screening has uncovered vast numbers of novel genes involved in the control of the immune system. This thesis describes the characterization of a novel mutant, Captain Morgan (CPM), originally identified in an immunization screen designed to evaluate both the initial antibody response to antigen and the ability to sustain antibody production. Mapping of this mutant lead to the identification of a single base pair mutation in a novel guanine nucleotide exchange factor, dedicator of cytokinesis 8 (DOCK8). The mutation was found to result in altered gene splicing of the DOCK8 protein leading to the truncation of the protein and loss of catalytic function. The importance of understanding the role of DOCK8 in host immunity has been recently underlined by the discovery that cohorts of patients suffering from autosomal recessive forms of hyper-IgE syndrome have loss-of-function or deletions in this novel guanine nucleotide exchange factor. Disease in these patients is characterised by recurrent viral and bacterial infections mainly of the skin and lungs, with reduced levels of peripheral CD4⁺ and CD8⁺ T cells in the blood of patients. Patients also have high levels of IgE and eosinophilia in the blood and are highly atopic with increased prevalence of allergic diseases including asthma. Loss of DOCK8 function results in a number of phenotypes in CPM mice, which may help understand the immunodeficiency syndrome experienced by DOCK8 deficient patients. CPM mice, like DOCK8 deficient patients, are lymphopenic with losses of both CD4⁺ and CD8⁺ T cells in the blood and secondary lymphoid organs. Challenge of CPM mice with modified vaccina virus (MVA) and influenza strain X31 demonstrated normal primary anti-viral responses. However, similar to the loss of germinal centre B cells previously described in these mice, memory T cell responses were diminished, which may explain the susceptibility of DOCK8 deficient patients to recurrent infections. In addition to the loss of peripheral T cells, rare populations of lymphocytes such as invariant natural killer T cells (iNKT) were also reduced in the liver and thymus. Due to their roles in bacterial and viral responses and cancer immunosurveillance it is expected that loss of these cells will contribute to disease severity. Together these findings illustrate the importance of the ENU mutagenesis model for generating new mutants, which can enhance our understanding of mammalian genes and create disease models of human disease. Further characterization of DOCK8 deficiency and the molecular mechanisms of DOCK8 function will have important implications for disease diagnosis and ongoing treatment for patients.

A fibrose pulmonar é uma via comum de várias doenças agudas e crônicas do interstício pulmonar que pode resultar na cicatrização anormal do pulmão. Há acúmulo excessivo das proteínas da matriz extracelular levando a desestruturação das paredes alveolares, e consequente perda das trocas gasosas pelos pulmões. As células NKT são grande fonte de citocinas e podem ser cruciais na polarização de macrófagos para o fenótipo M2. O projeto tem a hipótese de que as células NKT podem influenciar o desenvolvimento da fibrose pulmonar via modulação de macrófagos. Para isso, animais selvagens e knockout para células NKT invariante (Ja18-/-) foram submetidos ao protocolo de indução de fibrose pulmonar pela bleomicina. Os resultados indicam que o grupo Ja18-/- assim como os grupos experimentais que receberam agonistas para células NKT apresentaram uma proteção contra a fibrose pulmonar uma vez que houve menor síntese de hidroxiprolina, deposição de colágeno, citocinas pró-fibróticas e a manutenção de macrófagos M1 no tecido pulmonar. / Pulmonary fibrosis is a common pathway of various acute and chronic interstitial lung diseases that may result in abnormal healing of the lung. There is excessive accumulation of extracellular matrix proteins, leading to disruption of the alveolar walls and the consequent loss of gas exchange through the lungs. NKT cells are a big source of cytokines and may be crucial in the polarization of macrophages to the M2 phenotype. This project has hypothesized that NKT cells can influence the development of pulmonary fibrosis through modulation of macrophages. For this, wild and knockout invariant NKT cells (Ja18-/-) mice were subjected to the protocol of bleomycin induced pulmonary fibrosis. The results indicate that the group Ja18-/- as well as the experimental groups receiving agonists for NKT cells showed protection against lung fibrosis since there was less synthesis of hydroxyproline, collagen deposition, pro-fibrotic cytokines and maintenance of macrophages M1 in lung tissue.

As células NKT compreendem um grupo distinto de linfócitos caracterizados pela reatividade a glicolipídios apresentados pela molécula CD1d. Em nosso trabalho, nós investigamos a participação das células NKT na homeostase intestinal utilizando animais nocautes para essas células e também caracterizamos os subtipos de NKT no intestino. Nos animais nocautes observamos que a ausência de células NKT influencia a microbiota e a homeostase intestinal. Os animais nocautes possuem diminuição no filo Firmicutes, diminuição dos níveis de IgA nas fezes e de TGF-β no intestino. Esses animais também são mais suscetíveis à colite induzida por DSS, apresentando menor sobrevida, menor tamanho do cólon e aumento no score. Nos animais selvagens, a indução do subtipo NKT10 diminuiu a inflamação intestinal, não causou intensa redução do cólon e reduziu a frequência de células NKT e do subtipo NKT17 no intestino. Nossos resultados indicam que as células NKT intestinais são peças importantes para a homeostase intestinal e para a composição da microbiota intestinal. / NKT cells comprise a distinct group of lymphocytes characterized by their reactivity to glycolipids presented by CD1d. In our work, we investigated the involvement of NKT cells in intestinal homeostasis using knockout (KO) mice and we also characterized NKT subtypes in the intestine. The absence of NKT cells in KO mice influenced the intestinal microbiota and homeostasis. KO mice had a decrease in the Firmicutes phyla, in the levels of fecal IgA and TGF-β in the intestine. These mice are also more susceptible to DSS-induced colitis, exhibiting worse survival, severe shortening of the colon and higher score. In wild type mice, the induction of the NKT10 subtype decreased intestinal inflammation, did not cause intense reduction of colon and reduced the frequency of NKT cells and the NKT17 subtype in the intestine. Our results indicate that intestinal NKT cells are important for intestinal homeostasis and microbiota composition.