Thesis (doctoral)--Rijksuniversiteit te Utrecht, 1981. / English, summary and foreword in Dutch. Includes bibliographies.

Regulation of the immune system and of uterine tissue homeostasis, growth, and remodelling are deeply intertwined during pregnancy and are essential for successful reproduction. Recent findings showed that tissue-resident innate lymphoid cells (ILCs) are crucial regulators of both physiology and pathology of the tissues they populate. Uterine natural killer (uNK) cells are a subtype of ILCs known to regulate trophoblast invasion, uterine vascular adaptation to pregnancy, and foetal growth. We recently described additional types of ILCs in the uterus of women and mice. However, the role of these ILCs during reproduction is unknown. Among them, group 2 ILCs (ILC2s) have been previously characterised in other tissues, in which they modulate immune cells and tissue homeostasis by producing type-2 cytokines and growth factors (i.e. IL-4, IL-5, IL-13, and Amphiregulin). Based on these premises, I hypothesized that uterine ILC2s (uILC2s) regulate uterine immune homeostasis and thus contribute to successful reproduction. To test this, I first characterised the uILC subtypes present in humans and mice at various stages of the reproductive cycle. Secondly, I addressed the functional role of uILC2s during pregnancy by taking advantage of a uILC2 knockout mouse model. My results show that uterine ILC2s represent < 1% and < 0.1% of murine and human uterine leukocytes, respectively. However, as they can quickly produce large amounts of cytokines, uILCs are capable of potently affect both other immune cells and the surrounding tissue. Indeed, I found that compared to other tissue-resident ILC2s, uILC2s produce high levels of IL-5 and Areg even in the absence of any stimulation. On the contrary, non-uterine ILC2s mainly produce IL-13, which is lowly expressed by uILC2s. To further characterize the tissuespecific properties of uILC2s, I then performed RNAseq on uILC2s isolated from virgin, midgestation, and term murine uterus, and I compared their transcriptomes with those of ILC2s from lung, intestine, and bone marrow. Interestingly, uILC2s specifically express granzymes and genes typical of regulatory T cells. Therefore, uILC2s have tissue-specific properties and are modulated during pregnancy. Furthermore, the ability of uILC2s to produce IL-5 and Areg suggests that they may be crucial in the regulation of uterine type-2 immunity. I then studied the phenotype of $Rora^{flox/flox}Il7ra^{cre/wt}$(ILC2KO) mouse models, as well as that of mice lacking the ILC2 activating cytokine IL-33 ($IL33^{cit/cit}$; IL33KO). I examined the immune microenvironment in both the myometrium and decidua in ILC2KO mice and found alterations in type-2 cytokines and myeloid cell homeostasis. In particular, in absence of ILC2s, IL-4 and IL-5 are dramatically reduced, IL-13 is absent, and decidual inflammatory cytokines IL1β and IL-6 are increased. Furthermore, uterine dendritic cells (uDC), uterine macrophages (uMac), and uterine neutrophils (uN) increase, while uterine eosinophils (uEo) are virtually absent. These results show that uILC2s regulate uterine type-2 immunity, suggesting that uILC2s could be important during pregnancy. Accordingly, I found that lack of uILC2s leads to insufficient spiral artery remodelling and restricted foetal growth. Type-2 cytokines and in particular IL-4 regulates alternative activation of Macrophages (Mac) and Dendritic Cells (DCs), which promote the development of an anti-inflammatory environment and facilitate tissue remodelling. I hypothesised that similar mechanisms occur in the uterus and that uILC2s have a central role in the polarisation of the immune response. To explore this, I studied in more detail the characteristics of uEo, uMac, and uDCs dissected from wild type and ILC2KO mice. I found a reduction in genes associated with alternative activation in uMac and uDCs in the uterus of pregnant ILC2KO mice. Additionally, I showed that uEo are the main producers of the IL-4. This demonstrates that uILC2s promote alternative activation of myeloid cell population by modulating the uterine immune microenvironment. I then assessed the role of uILC2s-dependent type-2 immunity in inflammatory pathology following a type-1 response to bacterial infection. When challenged with LPS, pregnant ILC2KO mice showed more pronounced foetal demise. Therefore, uILC2s regulate uterine type-2 immune homeostasis and this prevents inflammatory pathology. Collectively, my work advances our knowledge of the innate immune mechanisms that control physiological and pathological events during pregnancy. These findings have implications to the field of immunology of pregnancy and may lead to clinical progress in diagnosis and prevention of infection-induced abortion in human pregnancies.

It seemed desirable to investigate further the possible role of complement and its components in the protective action of serum against transplanted neoplasms. It is the purpose of this thesis to present data which suggest that the C'4 component plays an active part in this process though the mechanism is not disclosed.

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The accumulation of leukocytes in non-lymphoid tissues and their structural organization into tertiary lymphoid structures (TLS), a process known as ectopic lymphoid neogenesis (ELN), is observed in response to chronic inflammation and in the target organ of several autoimmune diseases. TLS strongly resemble secondary lymphoid organs with specialised high-endothelial venules (HEV), segregated B/T cell areas and presence of follicular dendritic cells (FDC) networks promoting in situ affinity maturation of the antibody response. TLS have been associated with a growing number of autoimmune conditions and usually their presence is prognostic for undesirable disease progression. In Sjögren’s syndrome (SS), an autoimmune disease affecting the salivary and lachrymal glands leading to exocrine dysfunction, TLS develop in the salivary glands (SG) of around one-third of the patients. The immunobiology of the SG and the pathogenesis of SS have been poorly clarified and to date a robust and reproducible inducible animal model of SS and TLS in the SG is still absent. In my PhD, I developed and validated a novel inducible model of ELN in murine SG that also reproduces several features of SS. The retrograde administration of a replication-deficient adenovirus (AdV) in the SGs of wild-type C57Bl/6 mice was able to induce within three weeks fully formed TLS that displayed B/T cell segregation, FDC networks, HEVs and were positive for markers of germinal centres. Moreover, the AdV-treated mice showed a significant reduction of salivary flow and in 75% of the cases development of anti-nuclear antibodies.

Thesis (doctoral)--Katholieke Universiteit te Nijmegen.

No description available.

Introduction: Atopic dermatitis (AD) is characterized by chronic pruritic relapsing eczematous lesions of the skin. Eosinophilic inflammation in AD is driven by activation of type 2 inflammatory cells including CD4+ T cells and type 2 innate lymphoid cells (ILC2s). We have shown that type 2 cytokines, namely interleukin (IL)-5 and IL-13, stimulate migration and terminal differentiation of eosinophil progenitor cells (EoPs). We propose that these cytokines are important drivers of tissue eosinophilia in AD lesional skin. This study aimed to quantify, by flow cytometry, cells that produce type 2 cytokines in lesional skin compared to peripheral blood from moderate-severe AD patients. Methods: In a cross-sectional study of patients with moderate-to-severe AD (n=16), type 2 inflammatory cells were enumerated in blood and cells extracted from excised skin biopsies. By flow cytometry, live, singlet CD45+cells were identified as ILC2 (lin-CD127+CD294+), EoP (CD34+125+), and CD4+ T cells (Lin+CD3+CD4+). Intracellular expression of type 2 cytokines (IL-5 and IL-13) were evaluated in each cell population. In addition, we developed a protocol to enumerate ILC2s by fluorescence immune-histochemistry in lesional versus non-lesional skin samples and skin biopsies taken 24h post-intradermal challenge with allergen versus diluent. Data are expressed as median (interquartile range [IQR]) unless otherwise stated. Cross compartmental comparisons were made using the Wilcoxon rank-sum test and where applicable, correlational analyses were performed using a Spearman’s rank-correlational test. Results: There was a significantly higher number of total ILC2s in lesional skin compared to blood from AD subjects (556 [99 – 5501] vs 235 [67 – 569] cells/mL, p=0.03). Similarly, IL-5+, IL-13+ ILC2s, were significantly greater in skin compared to blood (6 [1 – 666] vs 1 [1 – 19] cells/mL, p=0.03; 28 [1 – 1357] vs 1 [1 – 7] cells/mL, p=0.01, respectively). We found higher numbers of total and type 2 cytokine positive EoP in lesional skin biopsies from AD patients compared to blood (Total EoP: 815 [285 – 2794] vs 112 [46 – 247] cells/mL, p<0.01; IL-5+EoP: 36 [1 – 129] vs 1 [1 – 23] cells/mL, p=0.07; IL-13+EoP: 92 [10 – 182] vs 1 [1 – 8] cells/mL, p<0.01 and IL-5+IL-13+ILC2: 70 [1 – 158] vs 1 [1 – 12] cells/mL, p=0.02, respectively). In contrast, significantly higher numbers of total and type 2 cytokine positive CD4+ cells were found in blood compared to lesional skin biopsies from AD patients (Total CD4+: 1092 [650 – 1742] vs 58.3 [35.3– 152.4] x 103 cells/mL, p<0.01 and IL-5+IL-13+CD4+ cells: 13.5 x 103 [2.1 x 103 – 42.9 x 103] vs 3.8 x 103 [1.6 x 103 – 4.9 x 103] cells/mL, p=0.02, respectively). For IF staining, there was a significant higher number of ILC2s in lesional compared to non-lesional skin biopsies and biopsies taken 24h post allergen- compared to diluent challenge (1 [0 – 2] vs 0 [0 - 0] cells/mm2, p=0.008, and 2 [1 – 2] vs 0 [0 – 0] cells/mm2, p=0.0002, respectively). Interestingly, in sex analyses we found significantly greater levels of blood ILC2 in females compared to males, but this not was found in the skin. Importantly, we found a significant correlation between lesional skin levels of ILC2 measured by flow cytometry and clinical measures of disease severity/symptoms as reported/calculated from the Patient-Oriented Eczema Measure questionnaire (POEM) score (total ILC2: r=0.55, p=0.04; IL-13+ ILC2s, r=0.61, p=0.02 and IL-5+ IL-13+ ILC2s: r=0.75, p=0.002). Conclusions: Preferential increases in skin-resident ILC2 that produce a type 2 rich environment were found in AD subjects. These levels correlated with patient-oriented measure of disease severity. We propose that this increase may encourage recruitment of mature eosinophils and EoP and possibly drive localized differentiation of EoP into mature eosinophils that may drive the pathology of AD lesions. Furthermore, immunofluorescence staining may be a suitable alternative to flow cytometry for identification of ILC2 in the event of a low cell count. These techniques can be used in future studies that target ILC2 biology to fully understand the role of these cells in driving AD. / Thesis / Master of Science (MSc)

Foot-and-mouth disease virus (FMDV) is one of the most contagious viruses of animals and is recognised as the most important constraint to international trade in animals and animal products. Two fundamental problems remain to be understood before more effective control measures can be put in place. These problems are the FMDV „carrier state‟ and the short duration of immunity after vaccination which contrasts with prolonged immunity after natural infection. The aim of this thesis was to study the interaction between FDMV and cells in lymphoid tissue in the natural bovine host, in order to improve our understanding of the protective immune response. Using laser capture microdissection in combination with quantitative real-time reverse transcription polymerase chain reaction, immunohistochemical analysis and corroborated by in situ hybridization, it is shown that FMDV locates rapidly to, and is maintained in, the light zone of germinal centres following primary infection of naïve cattle. Maintenance of non-replicating FMDV in these sites may represent a source of persisting infectious virus and also contribute to the generation of long-lasting antibody responses against neutralising epitopes of the virus. The role of T-lymphocyte subsets in recovery from FMDV infection in calves was investigated by administering subset-specific mouse monoclonal antibodies. Depletion of circulating CD4+ or WC1+ γδ T cells was achieved for a period extending from before challenge to after resolution of viraemia and peak clinical signs, whereas CD8+ cell depletion was only partial. Depletion of CD4+ cells was also confirmed by analysis of lymph node biopsies 5 days post-challenge. Depletion with anti-WC1 and anti-CD8 antibodies had no effect on the kinetics of infection, clinical signs and immune responses following FMDV infection. Three of the four CD4+ T-cell-depleted calves failed to generate an antibody response to the non-structural polyprotein 3ABC, but generated a neutralising antibody response similar to that in the controls, including rapid isotype switching to IgG antibody. These data suggest that antibody responses to sites on the surface of the virus capsid are T cell-independent whereas those directed against the non-structural proteins are T cell-dependent. CD4 depletion was found to substantially inhibit antibody responses to the G-H peptide loop VP1135-156 on the viral capsid, indicating that responses to this particular site, which has a more mobile structure than other neutralising sites on the virus capsid, are T cell-dependent. Depletion of CD4+ T cells had no adverse effect on the magnitude or duration of clinical signs or clearance of virus from the circulation. In conclusion, CD4+ T-cell-independent antibody responses play a major role in the resolution of primary infection with FMDV in cattle.

Over the past four years, a previously unrecognised family of innate effector cells has been identified. Their comprehensive functional capabilities range from lymphoid organogenesis, tissue remodelling, wound healing, immune protection and homeostasis to contribution to inflammation and allergic responses. Here we investigate the presence and function of type 2 innate lymphoid cells (ILC2) in the skin. We show that human ILC2 are resident in human skin and express RORA and GATA3, and skin homing receptors. ILC2 further infiltrate the skin after allergen challenge, where they produce the type 2 cytokines IL-5 and IL-13. Skin-derived ILC2 express the IL-33 receptor ST2, which is up-regulated during activation. Signalling via IL-33 induces type 2 cytokine and amphiregulin expression, and increases ILC2 migration. Atopic dermatitis (AD) is a chronic inflammatory skin disorder. Current evidence suggests that both skin barrier dysfunction and immune system abnormalities, particularly those of a type 2 phenotype, contribute to disease pathogenesis. We demonstrated that ILC2 are enriched in lesional skin biopsies from atopic patients and show higher expression of cytokine receptors, reflecting an activated phenotype. Down-regulation of E-cadherin is characteristic of filaggrin insufficiency, a cardinal feature of AD. Interestingly, E-cadherin binding to KLRG1 on human ILC2 dramatically inhibits IL-5 and IL-13 production. ILC2 may contribute to increases in type 2 cytokine production in the absence of the inhibitory E-cadherin ligation through this novel mechanism of barrier sensing. CRTH2, a receptor for prostaglandin D₂ (PGD₂), is expressed by human ILC2. However, the function of CRTH2 in these cells is unclear. We sought to determine the role of PGD₂ and CRTH2 in human ILC2 and compare it with that of the established ILC2 activators IL-25 and IL-33. PGD₂ binding to CRTH2 induced ILC2 migration and production of type 2 cytokines IL-4, IL-5, IL-13 and release of other pro-inflammatory cytokines IL-3, IL-8, IL-9, IL-21, GM-CSF, and CSF-1 in a dose-dependent manner. ILC2 activation through CRTH2 also upregulated the expression of IL-33 and IL-25 receptor subunits (ST2 and IL-17RA) suggesting a synergistic role. The effects of PGD₂ on ILC2 could be mimicked by the supernatant from activated human mast cells and inhibited by a CRTH2 antagonist. Therefore, PGD₂ can be considered as an important and potent activator of ILC2 through CRTH2 mediating strong inflammatory responses. Cell surface interaction mechanisms that activate ILC2 function are unknown. We observed the expression of NKp30 on ILC2 ex vivo and after culture. Using quantitative PCR we confirmed that ILCs express NKp30c splice variant, an immune-modulatory isoform. Incubation of ILC2 with the NKp30 ligand B7H6 and tumour cell lines expressing this protein induced production of type 2 cytokines. This interaction can be inhibited by NKp30 blocking antibodies. We further established that activation of NKp30 induces the canonical pathway of NFƙB signalling. Overall the work in thesis shows for the first time that ILC2 are resident in human skin and infiltrate rapidly after allergen challenge and in AD lesional skin. We have defined cytokine and lipid mediators that contribute to migration and activation of ILC2 and shown that KLRG1 and NKp30 act as inhibitory and activatory receptors respectively. The work defines novel pathways for barrier sensing and cutaneous inflammation, and identifies potential new targets for therapeutic intervention.