Produzida por macrófagos e células dendríticas, a IL-27 é uma citocina heterodimérica capaz de induzir células Tr1 produtoras de IL-10 e consequentemente regular linfócitos Th1, Th2 e Th17, dependendo da doença envolvida. Partindo-se do pressuposto de que a infecção causada por Trypanosoma cruzi normalmente induz miocardite refletida pela migração intensa de linfócitos Th1 para o tecido cardíaco, nós analisamos o papel regulador da IL-27 nesta condição inflamatória. Nós inicialmente verificamos que a IL-27 foi prontamente induzida in vitro em células infectadas com T. cruzi. Para gerar miocardite intensa coordenada por linfócitos Th1, nós polarizamos linfócitos T naïves para o padrão Th1 na ausência de moléculas relacionadas ao perfil Th17 (camundongos IL-17R-/-, IL-23-/- e IL-6-/-). Como esperado, a inflamação cardíaca intensa e o dano tecidual foram observados na ausência das moléculas do padrão Th17, o que contribuiu para a morte prematura dos animais IL-17R-/-, IL-23-/- e IL-6-/-, precisa e notoriamente pela indução da migração excessiva de linfócitos Th1 para o tecido cardíaco via CXCL-9 e CXCL-10. Para explorar os mecanismos pelos quais a IL-27 controla a miocardite induzida pelo T. cruzi, nós encontramos um recrutamento substancial de macrófagos produtores de IL-27 para o tecido cardíaco, o qual foi mediado pelas quimiocinas CCL3 e CCL4 na ausência de moléculas do padrão Th17. Para determinar quais os receptores necessários para a produção de IL-27, nós observamos que macrófagos derivados da medula óssea de camundongos deficientes de TLR4-/-, TLR9-/- e NLRP3-/- aboliram completamente a produção desta citocina após a infecção in vitro com T. cruzi, enquanto o receptor TLR2 foi dispensável. Nós também verificamos que macrófagos produtores de IL-27 suprimiram linfócitos Th1 através da indução de células Tr1 produtoras de IL-10 após a infecção com T. cruzi. Em seguida, nós avaliamos se a IL-27 foi correlacionada com a proteção cardíaca durante a doença de Chagas. Nós observamos níveis séricos elevados de IL-27 tanto em pacientes com a forma clínica indeterminada ou cardíaca leve, enquanto pacientes com cardiomiopatia moderada ou grave produziram níveis reduzidos de IL-27. Neste estudo, nós descrevemos um novo mecanismo regulador desempenhado por macrófagos produtores de IL-27 no controle da miocardite induzida por T. cruzi. Macrófagos produtores de IL-27 podem suprimir processos inflamatórios desencadeados por linfócitos Th1, os principais vilões na doença de Chagas. / IL-27 is a heterodimeric cytokine produced by macrophages and dendritic cells known to induce IL-10-producing Tr1 cells and to regulate Th1, Th2, and Th17 lymphocytes, depending on the underlying disease. Because the infection caused by Trypanosoma cruzi normally induces myocarditis mirrored by an outstanding migration of Th1 cells to the heart tissue, we analyzed the regulatory role of IL-27 in this inflammatory condition. We firstly verified that IL-27 was promptly induced by in vitro T. cruzi-infected spleen cells. To generate a robust myocarditis coordinated by Th1 lymphocytes, we polarized lymphocytes to a Th1 pattern by infecting mice in the absence of Th17-related molecules (IL-17R-/-, IL-23-/-, and IL-6-/- mice). As expected, an impressive cardiac inflammation and damage was observed in the absence of Th17-related molecules, leading IL-17R-/-, IL-23-/-, and IL-6-/- mice to the premature death, precisely and notably by inducing an exuberant Th1 migration to the heart tissue via CXCL9 and CXCL10 chemokines. To explore the mechanisms by which IL-27 controls T. cruzi-induced myocarditis, we found a striking recruitment of IL-27-producing macrophages to the heart tissue mediated by increased levels of CCL3 and CCL4 chemokines in the absence of Th17-associated molecules. To gain further insights into the receptors required to IL-27 production, we observed that bone marrow-derived macrophages from TLR4-/-, TLR9-/-, and NLRP3-/- mice completely abolished IL-27 production after in vitro T. cruzi infection, while TLR2 was dispensable. We also verified that IL-27-producing macrophages supressed Th1 lymphocytes by inducing IL-10-producing Tr1 cells after T. cruzi infection. We next assessed whether IL-27 was correlated to cardiac protection during Chagas Disease. We observed augmented serum levels of IL-27 in either patients with indeterminate (asymptomatic) form or mild cardiac form, whereas patients with moderate or severe cardiomyopathy were poor producers of IL-27. Here, we described a novel regulatory mechanism developed by IL-27-producing macrophages in the control of T. cruzi-induced myocarditis. IL-27-producing macrophages can suppress inflammatory processes caused by Th1 lymphocytes, the bona fide culprits of Chagas Disease.

<p>Since the mid 1900s the organizational perspective in media producing companies has changed. The focus has shifted from just being a laborer to the person behind the effort. The most important for an efficient and smooth organization is the motivation of the employees and the social working environment. Former research argues that managers must be coaches and that crucial factors for the survival of organizations are creativity, innovation and adaptability. With this study we investigate what motivates employees to use their creative skills. We also examine the leader’s importance concerning motivation and how this could lead to a more pleasant and productive organization. The focus is on media producing companies to obtain the media management perspective. The method we have chosen is qualitative research interviews. We have interviewed three leaders in three different media producing companies. We have used questionnaires where staff members were asked questions about their motivation, creativity, communication and experience of leadership. The analysis is based on our collected data and earlier research in this field. Our conclusions are that employees with careers in media producing organizations have many factors that affect motivation and creativity at work. Leaders have great influence and significant impact on these factors. Managers and people with leadership positions need an understanding and awareness of the employee’s whishes and their demands of the executives and the organization. To have a continuous assessment of employee satisfaction and their wishes is very effective. To educate both new and existing managers of the factors which affect the employees could be a winning concept.</p>

<p>Patients with systemic lupus erythematosus (SLE) have elevated levels of interferon (IFN)-α in blood and IFN-α-producing cells in tissues. In the present thesis, we investigate the mechanisms behind the upregulated IFN-α-production in SLE and also show that the IFN-α system is activated in primary Sjögren’s syndrome (pSS), with IFN-α-producing cells in the major affected organ, the salivary glands. The IFN-α is a type I IFN, a family of cytokines counteracting especially viral infections, by acting directly on infected cells, and via many immunomodulatory effects. The latter may also contribute to autoimmune processes.</p><p>The type I IFNs are usually produced upon recognition of microbial structures. In SLE, however, DNA-containing immune complexes (ICs) that induce IFN-α production are found. Many autoantibodies in SLE and pSS are directed to nucleic acids or to DNA/RNA-binding proteins. We show that also RNA in complex with autoantibodies from SLE or pSS patients (RNA-IC) induces IFN-α-production. The RNA could be either in the form of RNA-containing material released from apoptotic or necrotic cells or as a pure RNA-containing autoantigen, the U1 small nuclear ribonucleoprotein particle. </p><p>The IFN-α-production induced by RNA-IC occurred in plasmacytoid dendritic cells (PDCs), also termed natural IFN-producing cells (NIPCs), via binding to Fcγ-receptor IIa, endocytosis and triggering of Toll-like receptors (TLRs), probably TLR7 and TLR9. The RNA-IC may also have other effects, and we found that they induce prostaglandin E2 (PGE2) production in monocytes and tumor necrosis factor (TNF)-α in both monocytes and NIPC/PDC. The PGE2 downregulated the IFN-α induction in NIPC/PDC, and the IFN-α induction was increased in monocyte-depleted cell cultures. </p><p>The findings presented in this thesis aids in the understanding of the mechanisms behind the activated IFN-α system in SLE and other autoimmune diseases, and shows that also pSS is one of these diseases.</p>

<p>In this study, metastasizing serotonin-producing ileocaecal carcinoid tumours (MSPCs) were examined for biological characteristics that could be used to define clinically relevant subgroups within this patient population. Possible targets for new treatment options were also explored.</p><p>It was found that MSPCs share several biological characteristics such as expression of serotonin, tachykinins (TKs), chromogranin A, islet autoantigen-2 and connective tissue growth factor (CTGF). TKs and serotonin were demonstrated in the same endocrine tumours in the gut and lung. IA-2 expression was shown to be up-regulated in MSPCs, possibly in connection with active hormone secretion. CTGF expression was high in tumour areas adjacent to extensive stroma expressing alpha-smooth muscle actin. This indicated myofibroblast differentiation, which may be associated with fibrosis-related complications prevalent in patients with MSPCs. When compared with other endocrine tumours, MSPCs behaved as a relatively homogeneous group, though within the MSPC population several subgroups could be defined. Patients with tumours displaying either a solid growth pattern and/or a Ki67 index ≥1% had a less favourable prognosis than those who did not. Another group of patients, who had increased plasma TK concentrations, were more likely to suffer from severe diarrhea. This information should be considered when discussing clinical treatment and when undertaking tumour biological studies. New treatment possibilities, such as drugs that specifically target TK receptors and antibodies to CTGF, are also discussed.</p><p>In conclusion, MSPCs comprise a clinically relevant tumour group with similar biological features that are distinct from other endocrine tumours. Subgroups of patients within this patient category can be defined which may be relevant when establishing prognosis and when selecting future treatment modalities.</p>

Homogene Immunoassays sind immunologische Testverfahren, bei deren Durchführung vollständig auf Separations- und Waschschritte verzichtet werden kann. Der Substrate Channeling Immunoassay beruht auf der Weitergabe eines Substrates in einem immunologischen Komplex aus zwei Enzymen. Das Produkt des ersten Enzyms dient dem zweiten Enzym als Substrat zur Generierung eines photometrisch nachweisbaren Produktes. Voraussetzung für diese Weitergabe ist die enge räumliche Nähe beider Enzyme. Diese Nähe wird durch eine Bindung zwischen Analyt und anti-Analyt Antikörper vermittelt. Ein solcher Substrate Channeling Immunoassay wurde unter Verwendung der Enzyme Glucoseoxidase und Peroxidase aufgebaut. Das so etablierte System war funktionstüchtig, jedoch blieb seine Sensitivität hinter der normaler, heterogener Immunoassays zurück. Die Grundlage eines Fluorescence Quenching Immunoassays ist der gegenseitige Ausschluß zweier Antikörper bei der Bindung eines Dihapten-Konjugates. Das Konjugat besteht dabei aus dem Analyten und einem Fluorophor. Die beiden um die Konjugatbindung konkurrierenden Antikörper sind ein anti-Analyt Antikörper und ein anti-Fluorophor Antikörper, der zudem über die Eigenschaft verfügt, bei Bindung des Fluorophors dessen Fluoreszenz zu löschen. Externe Gaben des freien Analyten verschieben das eingestellte Gleichgewicht in Richtung Fluorophor-Bindung und damit Fluoreszenz-Löschung. Die Änderung der Fluoreszenz ist direkt an die Konzentration des freien Analyten gekoppelt und dient zu deren Bestimmung. Ein solcher Fluorescence Quenching Immunoassays wurde für die Konzentrationsbestimmung des Herbizides Diuron etabliert. Die erreichten Sensitivitäten erlauben die praktische, immundiagnostische Anwendung des Systems. Ein Dihapten-Konjugat wurde ebenfalls zum Aufbau eines Verfahrens zur Selektion Antikörper produzierender Zellen eingesetzt. Die Selektion der Antikörper produzierenden Zellen erfolgt unter Verwendung eines Toxinkonjugates. Dieses Konjugat besteht aus einem Liganden und einem Toxin. Die Antikörperbindung des Liganden behindert sterisch die Wechselwirkung der Toxinkomponente im Konjugat mit deren Zielstruktur in oder auf der Zelle. Nur Zellen die einen geeigneten Antikörper sezernieren, überleben die Selektion und reichern sich in der Kultur an. Das Selektionsverfahren wurde erfolgreich für die Selektion von E.coli Zellen eingesetzt, die einen rekombinanten, Fluorescein bindenden Antikörper produzierten. Das hierfür synthetisierte Toxinkonjugat bestand aus Fluorescein (Ligand) und Ampicillin (Toxinkomponente). Eine Ablösung der bisher für diese Aufgabe gebräuchlichen, außerordentlich kostenintensiven, Screening Methoden wird damit möglich. / Homogeneous immunoassays are test systems which do not depend on separation steps. The substrate channeling immunoassay is based on the product/substrate transfer in an immunological complex built up by two enzymes. The product of the first enzyme functions as substrate for the second enzyme. The second enzyme generates a photometrically detectable product. The close proximity of these two enzymes is the basis of the substrate channeling. This proximity is created by antibody binding to the corresponding analyte. The enzymes glucose oxidase and peroxidase were used for the development of such an assay system. The established homogeneous immunoassay was functional. But the sensitivity of the assay was much lower than that of conventional heterogeneous immunoassays. The principle of a fluorescence quenching immunoassay is based on the fact that two antibodies exclude each other from binding to a dihapten conjugate. The conjugate consists of the analyte and the fluorophore. The two antibodies which compete for the conjugate binding are an anti-analyte antibody and an anti-fluorophore antibody. This anti-fluorophore antibody quenches the fluorescence of the fluorophore after binding. The addition of free analyte alters the equilibrium of the system so that the anti-fluorophore antibody is bound to the fluorophore and the fluorescence is quenched. The change in fluorescence is therefore an indicator of the concentration of free analyte added. A homogeneous fluorescence quenching immunoassay was established for the determination of the herbicide diuron. The sensitivities obtained allow the practical immunodiagnostic application of the system. A dihapten conjugate was also employed for the development of a selection method for antibody-producing cells. Toxin conjugates were used in this system. Each conjugate consisted of a ligand and a toxin. Antibody binding to the ligand sterically inhibits the toxin component to interact with its target structure. Only cells secreting a binding antibody will survive the selection and will accumulate in culture. The system was applied to the selection of E.coli cells producing a recombinant fluorescein-binding antibody. The toxin conjugate used in experiment consisted of fluorescein (ligand) and ampicillin (toxin component). This selection procedure allowed the isolation of recombinant antibody-producing E.coli cells. It has the potential to replace the time-consuming and labour-intensive methods used so far.

Patients with systemic lupus erythematosus (SLE) have elevated levels of interferon (IFN)-α in blood and IFN-α-producing cells in tissues. In the present thesis, we investigate the mechanisms behind the upregulated IFN-α-production in SLE and also show that the IFN-α system is activated in primary Sjögren’s syndrome (pSS), with IFN-α-producing cells in the major affected organ, the salivary glands. The IFN-α is a type I IFN, a family of cytokines counteracting especially viral infections, by acting directly on infected cells, and via many immunomodulatory effects. The latter may also contribute to autoimmune processes. The type I IFNs are usually produced upon recognition of microbial structures. In SLE, however, DNA-containing immune complexes (ICs) that induce IFN-α production are found. Many autoantibodies in SLE and pSS are directed to nucleic acids or to DNA/RNA-binding proteins. We show that also RNA in complex with autoantibodies from SLE or pSS patients (RNA-IC) induces IFN-α-production. The RNA could be either in the form of RNA-containing material released from apoptotic or necrotic cells or as a pure RNA-containing autoantigen, the U1 small nuclear ribonucleoprotein particle. The IFN-α-production induced by RNA-IC occurred in plasmacytoid dendritic cells (PDCs), also termed natural IFN-producing cells (NIPCs), via binding to Fcγ-receptor IIa, endocytosis and triggering of Toll-like receptors (TLRs), probably TLR7 and TLR9. The RNA-IC may also have other effects, and we found that they induce prostaglandin E2 (PGE2) production in monocytes and tumor necrosis factor (TNF)-α in both monocytes and NIPC/PDC. The PGE2 downregulated the IFN-α induction in NIPC/PDC, and the IFN-α induction was increased in monocyte-depleted cell cultures. The findings presented in this thesis aids in the understanding of the mechanisms behind the activated IFN-α system in SLE and other autoimmune diseases, and shows that also pSS is one of these diseases.

In this study, metastasizing serotonin-producing ileocaecal carcinoid tumours (MSPCs) were examined for biological characteristics that could be used to define clinically relevant subgroups within this patient population. Possible targets for new treatment options were also explored. It was found that MSPCs share several biological characteristics such as expression of serotonin, tachykinins (TKs), chromogranin A, islet autoantigen-2 and connective tissue growth factor (CTGF). TKs and serotonin were demonstrated in the same endocrine tumours in the gut and lung. IA-2 expression was shown to be up-regulated in MSPCs, possibly in connection with active hormone secretion. CTGF expression was high in tumour areas adjacent to extensive stroma expressing alpha-smooth muscle actin. This indicated myofibroblast differentiation, which may be associated with fibrosis-related complications prevalent in patients with MSPCs. When compared with other endocrine tumours, MSPCs behaved as a relatively homogeneous group, though within the MSPC population several subgroups could be defined. Patients with tumours displaying either a solid growth pattern and/or a Ki67 index ≥1% had a less favourable prognosis than those who did not. Another group of patients, who had increased plasma TK concentrations, were more likely to suffer from severe diarrhea. This information should be considered when discussing clinical treatment and when undertaking tumour biological studies. New treatment possibilities, such as drugs that specifically target TK receptors and antibodies to CTGF, are also discussed. In conclusion, MSPCs comprise a clinically relevant tumour group with similar biological features that are distinct from other endocrine tumours. Subgroups of patients within this patient category can be defined which may be relevant when establishing prognosis and when selecting future treatment modalities.

Since the mid 1900s the organizational perspective in media producing companies has changed. The focus has shifted from just being a laborer to the person behind the effort. The most important for an efficient and smooth organization is the motivation of the employees and the social working environment. Former research argues that managers must be coaches and that crucial factors for the survival of organizations are creativity, innovation and adaptability. With this study we investigate what motivates employees to use their creative skills. We also examine the leader’s importance concerning motivation and how this could lead to a more pleasant and productive organization. The focus is on media producing companies to obtain the media management perspective. The method we have chosen is qualitative research interviews. We have interviewed three leaders in three different media producing companies. We have used questionnaires where staff members were asked questions about their motivation, creativity, communication and experience of leadership. The analysis is based on our collected data and earlier research in this field. Our conclusions are that employees with careers in media producing organizations have many factors that affect motivation and creativity at work. Leaders have great influence and significant impact on these factors. Managers and people with leadership positions need an understanding and awareness of the employee’s whishes and their demands of the executives and the organization. To have a continuous assessment of employee satisfaction and their wishes is very effective. To educate both new and existing managers of the factors which affect the employees could be a winning concept.

ESBL-producing Enterobacteriaceae are emerging worldwide and they are frequently multi-drug resistant, thus limiting treatment options for infections caused by these pathogens. The overall aim of the thesis was to investigate ESBL-producing Enterobacteriaceae in a Swedish county. First, we developed a molecular method, a multiplex PCR assay for identification of SHV, TEM and CTX-M genes in clinical isolates of Enterobacteriaceae with an ESBL phenotype. From 2002 until the end of 2007 all isolates of ESBL-producing Enterobacteriaceae in Östergötland, Sweden were further investigated. The prevalence of ESBL-producing Enterobacteriaceae was low, &lt;1%, but increasing,while the antibiotic consumption remained unchanged. CTX-M enzymes, particularly CTX-M group 1, dominate in our region as well as in the rest of Europe. Furthermore, we have investigated antimicrobial susceptibility by performing MIC-testing in a large, well-characterized population of CTX-M-producing E. coli. Only three oral antimicrobial agents (fosfomycin, nitrofurantoin and mecillinam) demonstrated susceptibility above 90%. High susceptibility, &gt;90%, was also demonstrated for carbapenems, colistin, tigecycline and amikacin. Sixty-eight per cent of ESBL-producing E. coli was multi-resistant, and the most common multi-resistance pattern was the ESBL phenotype with decreased susceptibility to trimethoprim, trimethoprim-sulfamethoxazole, ciprofloxacin, gentamicin and tobramycin. Isolates belonging to CTX-M group 9 are generally more susceptible to antibiotics than the CTX-M group 1-producing E. coli. Finally, a prospective multicentre case-control study examined the prevalence of ESBL-producing Enterobacteriaceae in faecal samples before and after travel abroad and the risk factors of acquisition. Sixty-eight of 226 travellers (30%) had ESBL-producing Enterobacteriaceae in the faecal flora. The geographical area visited had the highest impact on acquisition, with highest the risk for travellers visiting the Indian subcontinent, followed by Asia and Africa north of the equator. Also, acquisition of ESBL-producing Enterobacteriaceae during travel is associated with abdominal symptoms such as diarrhoea. Age also seemed to affect the risk of acquiring ESBL-producing Enterobacteriaceae, the highest risks were found among travellers ≥ 65 years. This thesis has contributed to increased understanding of the epidemiology of ESBL-producing Enterobacteriaceae and their susceptibility to both beta-lactam and non-beta-lactam agents.

L’idée qu’une cellule puisse effectuer la cytolyse de cellules transformées, comme une cellule Natural Killer (NK), tout en ayant la capacité de présenter des antigènes, comme une cellule dendritique (DC), peut sembler fantaisiste. Cependant, de telles cellules furent bel et bien identifiées chez la souris en 2006. Ces cellules, nommées Interferon-producing Killer Dendritic Cells (IKDC), furent l’objet d’une caractérisation extensive qui révéla leur énorme potentiel immunologique. La combinaison de fonctions associées à des cellules NK et à des DC a doté les IKDC d’un pouvoir antitumoral remarquable. D’ailleurs, il a été démontré que les IKDC sont plus efficaces que les cellules NK pour limiter la croissance tumorale. Ainsi, suite à leur découverte, les IKDC ont suscité beaucoup d’intérêt. Cependant, une controverse émergea sur la nature des IKDC. Plusieurs groupes indépendants tentèrent de reproduire les expériences attestant les fonctions de DC des IKDC, sans y parvenir. De plus, des études additionnelles révélèrent que les IKDC possèdent des similitudes très importantes avec les cellules NK. Ces observations ont mené la communauté scientifique à suggérer que les IKDC sont des cellules NK en état d’activation (aNK). Malgré cette controverse, les caractéristiques antitumorales des IKDC sont si uniques et considérables qu’il est primordial de poursuivre l’étude de ces cellules. Pour y arriver, il est essentiel de déterminer la nature des IKDC et de mettre fin à ce débat. Par la suite, il sera important d’identifier des façons de cibler spécifiquement les IKDC pour permettre leur usage dans le cadre de thérapies antitumorales. Ainsi, l’objectif de cette thèse est de définir l’identité des IKDC, puis de déterminer les facteurs génétiques responsables de la régulation de ces cellules. Nous avons démontré que les IKDC ne sont pas des cellules aNK, contrairement à ce qui avait été suggéré. Nous avons constaté que les IKDC prolifèrent activement et possèdent un phénotype unique, des caractéristiques associées à des cellules NK très immatures. Afin de déterminer si les IKDC peuvent acquérir un phénotype mature, nous avons effectué des expériences de transfert adoptif. Suite à leur injection in vivo, les IKDC acquièrent un phénotype de cellules matures, mais étonnamment, elles se différencient aussi en cellules NK. Ainsi, nous avons révélé que les IKDC sont un intermédiaire dans la différenciation des cellules NK. En parallèle, nous avons démontré que la proportion d’IKDC varie grandement entre des souris de fond génétique différent, indiquant que des facteurs génétiques sont impliqués dans la régulation de ces cellules. Nous avons alors effectué une analyse génétique qui a révélé que les IKDC sont régulées par des facteurs génétiques compris dans une région distale du chromosome 7. Les résultats présentés dans cette thèse constituent une avancée importante pour la recherche sur les IKDC. Ils ont permis de définir la nature des IKDC et d’identifier un intervalle génétique impliqué dans la régulation de ces cellules. Ces découvertes sont des connaissances précieuses pour l’identification des IKDC chez l’Homme et la création de nouvelles thérapies dans la lutte contre le cancer. / The idea that a cell could kill transformed cells, like a Natural Killer (NK) cell, all the while exhibiting also the capacity to present antigens to T cells, like a Dendritic Cell (DC), may seem farfetched. However, in mice, a cell presenting these specific properties was identified in 2006. These cells were named Interferon-producing Killer Dendritic Cells (IKDC) and extensive studies revealed that they were endowed with an important immunological potential. Indeed, the fact that IKDCs exhibit properties of both DC and NK cells conferred them with an exceptional anti-tumor potential. Notably, on a per cell basis, the in vivo anti-tumor activity of IKDCs is more efficient than NK cells. Therefore, following their identification, IKDCs showed great therapeutic promise. However, a debate on the cell lineage origin of IKDCs emerged. Several independent groups could not replicate the finding that IKDCs showed functional antigen-presentation properties similar to DCs. Also, additional studies revealed that IKDCs are very similar to NK cells. These and other observations led the scientific community to believe that IKDCs were activated NK cells. Despite this controversy, IKDCs clearly exhibit a unique and outstanding anti-tumor potential, highlighting the relevance to further explore these cells. We must first close the debate regarding the lineage origin of IKDCs. We subsequently need to identify a means to specifically target IKDCs to facilitate their use in novel anti-tumor therapies. Thus, the objective of my thesis is first, to define the identity of IKDCs and second, to determine the genetic factors implicated in the regulation of these cells. For the first objective, we demonstrated that IKDCs do not represent activated NK cells, as previously suggested. We show that IKDCs are highly proliferative and exhibit a unique phenotype associated with very immature NK cells. In an attempt to verify if IKDCs could acquire a mature phenotype, we conducted an adoptive transfer experiment. We found that, after adoptive transfer, IKDCs adopt a mature phenotype, but also surprisingly differentiate into NK cells. These findings indicate that IKDCs represent an intermediate in NK-cell differentiation. For the second objective, we demonstrated that the IKDC proportion was highly variable between strains of different background origins, indicating that these cells are regulated by genetic factors. A genetic study revealed that genetic factors in distal arm of chromosome 7 associate with the proportion of IKDCs. The results presented in this thesis represent an important breakthrough for the research on IKDCs. They allowed to define the cell lineage origin of IKDCs and to identify a genetic region involved in the regulation of this cell type. These discoveries are valuable knowledge for the identification of human IKDCs and the development of novel anti-tumor therapies.