Adhesion and Migration of Monocytes and Dendritic Cells in Type 1 Diabetes

SAMENVATTING VOOR NIET-INGEWIJDEN Type 1 diabetes, vroeger ook wel jeugddiabetes genoemd, wordt gekenmerkt door een afweerreactie gericht tegen de insuline-producerende ß cellen. Bij deze afweerreactie valt het afweersysteem (immuunsysteem) de lichaamseigen ß cellen in de alvleesklier aan en vernietigt deze. Deze afweerreactie waarbij het lichaam zichzelf aanvalt wordt een auto-immuunreactie genoemd. Als gevolg van deze auto-immuunreactie vermindert de productie van insuline, die belangrijk is voor de glucose huishouding binnen het lichaam. Door de verminderde inType 1 diabetes is characterized by a T cell mediated destruction of the insulin-producing ß cells in the islets of Langerhans that are situated in the pancreas. Prior to the infiltration of lymphocytes into the pancreas, an accumulation of macrophages (mf) and dendritic cells (DC) is observed. It is generally thought that these mf and DC originate from blood monocytes that have entered the pancreas and have differentiated into mf or DC. On the basis of their normal physiological role, these cells presumably take up self-antigens and process these into peptides, which they present, after a so-called “steady-state” or “homeostatic” trafficking of the DC to the draining lymph nodes, to T lymphocytes in the para-cortical area. Normally this leads to tolerance induction and T regulatory cells are induced. However in the case of diabetes development, not regulatory T cells, but erroneously effector T lymphocytes become activated and islet autoimmunity is induced. These effector T cells that were primed in the lymph node, become re-activated after re-circulation upon recognition of the self-antigens in the pancreas and consequently – together with macrophages - initiate inflammation and mediate ß cell destruction, which is a hallmark of type 1 diabetes. In this thesis I have studied the processes involved in the early accumulation of mf and DC in the pancreas prior to the infiltration of lymphocytes. The extravasation of monocytes from the circulation into the pancreas is a complex process. Amongst other factors, adhesion molecules, chemokines and myeloid related proteins (MRPs) play an important role in the adhesive and migratory responses of the monocytes that enable effective extravasation. I studied the adhesive and migratory behaviour of human monocytes of type 1 diabetic patients and compared these functions with those of monocytes of type 2 diabetic patients and healthy control subjects. First of all, I was not able to detect any differences between patients and control subjects regarding the subdivision of circulating monocytes in mature and immature cells based on the expression of CD14 and CD16 (chapter 2.1). Secondly, monocytes of patients with type 1 diabetes displayed an intrinsically increased surface expression of the pro-inflammatory molecule MRP8/14 and an increased serum level of MRP8/14. When monocytes were allowed to adhere to the extra cellular matrix component fibronectin the cells showed an enhanced expression and production of MRP8/14. The monocytes of type 1 diabetes patients showed the strongest expression and production of MRP8/14 which was significantly increased over that of healthy control monocytes (chapter 2.2). Furthermore, such activated type 1 diabetic monocytes showed an even stronger adhesion to fibronectin, which was indeed found to be the effect of exposition of the monocytes to MRP8/14 (chapter 2.1). My findings suggest a positive feedback mechanism regarding the adhesive capacity of monocytes in type 1 diabetes: circulating monocytes express and secrete higher levels of MRP8/14 as compared to healthy control subjects, resulting in increased MRP8/14 in the serum. The increased serum MRP8/14 induces an increased adhesive capacity to fibronectin of the monocytes, which leads to an even larger secretion of MRP8/14 compared to healthy controls. In this thesis I also describe that the increased MRP8/14 in the serum induced an increased expression of CD11b/CD18 on the monocytes that is likely involved in the increased adhesion of the type 1 diabetic monocytes to endothelial cells that I observed (chapter 2.2). After the adhesion studies I investigated the migratory behaviour of monocytes of type 1 diabetes patients and observed a remarkably decreased response towards the pro-inflammatory chemokines CCL2 and CCL3. Both the transendothelial migration (measured in a Transwell system) and the chemotaxis (measured in the classical Boyden assay) towards these pro-inflammatory chem

The significance of soils and soil science towards realization of the United Nations sustainable development goals

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Functional gap junctions accumulate at the immunological synapse and contribute to T cell activation

Gap junction (GJ) mediates intercellular communication through linked hemichannels from each of two adjacent cells. Using human and mouse models, we show that connexin 43 (Cx43), the main GJ protein in the immune system, was recruited to the immunological synapse during T cell priming as both GJs and stand-alone hemichannels. Cx43 accumulation at the synapse was Ag specific and time dependent, and required an intact actin cytoskeleton. Fluorescence recovery after photobleaching and Cx43- specific inhibitors were used to prove that intercellular communication between T cells and dendritic cells is bidirectional and specifically mediated by Cx43. Moreover, this intercellular cross talk contributed to T cell activation as silencing of Cx43 with an antisense or inhibition of GJ docking impaired intracellular Ca2+ responses and cytokine release by T cells. These findings identify Cx43 as an important functional component of the immunological synapse and reveal a crucial role for GJs and hemichannels as coordinators of the dendritic cell-T cell signaling machinery that regulates T cell activation. Copyright © 2011 by The American Association of Immunologists, Inc

Vignette studies of medical choice and judgement to study caregivers' medical decision behaviour: systematic review

BACKGROUND: Vignette studies of medical choice and judgement have gained popularity in the medical literature. Originally developed in mathematical psychology they can be used to evaluate physicians' behaviour in the setting of diagnostic testing or treatment decisions. We provide an overview of the use, objectives and methodology of these studies in the medical field. METHODS: Systematic review. We searched in electronic databases; reference lists of included studies. We included studies that examined medical decisions of physicians, nurses or medical students using cue weightings from answers to structured vignettes. Two reviewers scrutinized abstracts and examined full text copies of potentially eligible studies. The aim of the included studies, the type of clinical decision, the number of participants, some technical aspects, and the type of statistical analysis were extracted in duplicate and discrepancies were resolved by consensus. RESULTS: 30 reports published between 1983 and 2005 fulfilled the inclusion criteria. 22 studies (73%) reported on treatment decisions and 27 (90%) explored the variation of decisions among experts. Nine studies (30%) described differences in decisions between groups of caregivers and ten studies (33%) described the decision behaviour of only one group. Only six studies (20%) compared decision behaviour against an empirical reference of a correct decision. The median number of considered attributes was 6.5 (IQR 4-9), the median number of vignettes was 27 (IQR 16-40). In 17 studies, decision makers had to rate the relative importance of a given vignette; in six studies they had to assign a probability to each vignette. Only ten studies (33%) applied a statistical procedure to account for correlated data. CONCLUSION: Various studies of medical choice and judgement have been performed to depict weightings of the value of clinical information from answers to structured vignettes of care givers. We found that the design and analysis methods used in current applications vary considerably and could be improved in a large number of cases

Wiskott-Aldrich syndrome protein regulates autophagy and inflammasome activity in innate immune cells.

Dysregulation of autophagy and inflammasome activity contributes to the development of auto-inflammatory diseases. Emerging evidence highlights the importance of the actin cytoskeleton in modulating inflammatory responses. Here we show that deficiency of Wiskott-Aldrich syndrome protein (WASp), which signals to the actin cytoskeleton, modulates autophagy and inflammasome function. In a model of sterile inflammation utilizing TLR4 ligation followed by ATP or nigericin treatment, inflammasome activation is enhanced in monocytes from WAS patients and in WAS-knockout mouse dendritic cells. In ex vivo models of enteropathogenic Escherichia coli and Shigella flexneri infection, WASp deficiency causes defective bacterial clearance, excessive inflammasome activation and host cell death that are associated with dysregulated septin cage-like formation, impaired autophagic p62/LC3 recruitment and defective formation of canonical autophagosomes. Taken together, we propose that dysregulation of autophagy and inflammasome activities contribute to the autoinflammatory manifestations of WAS, thereby identifying potential targets for therapeutic intervention

ICON.NL: coastline observatory to examine coastal dynamics in response to natural forcing and human interventions

In the light of challenges raised by a changing climate and increasing population pressure in coastal regions, it has become clear that theoretical models and scattered experiments do not provide the data we urgently need to understand coastal conditions and processes. We propose a Dutch coastline observatory named ICON.NL, based at the Delfland Coast with core observations focused on the internationally well-known Sand Engine experiment, as part of an International Coastline Observatories Network (ICON). ICON.NL will cover the physics and ecology from deep water to the dunes. Data will be collected continuously by novel remote sensing and in-situ sensors, coupled to numerical models to yield unsurpassed long-term coastline measurements. The combination of the unique site and ambitious monitoring design enables new avenues in coastal science and a leap in interdisciplinary research

Eenige waarnemingen aangaande den bloeddruk bij operaties

De bloeddrukmeting als klinische onderzoekingsmethode neemt sinds lange jaren een belangrijke plaats in bij de herkenning en behandeling van de ziekten der nieren van het bloedvaatstelsel. Daarnaast heeft men getracht deze zoo eenvoudige en betrouwbare onderzoekingsmethode ook op ander gebied der geneeskunde dienstbaar te maken. ... Zie: Inleiding

Wiskott–Aldrich Syndrome: Immunodeficiency resulting from defective cell migration and impaired immunostimulatory activation

Regulation of the actin cytoskeleton is crucial for many aspects of correct and cooperative functioning of immune cells, such as migration, antigen uptake and cell activation. The Wiskott–Aldrich Syndrome protein (WASp) is an important regulator of actin cytoskeletal rearrangements and lack of this protein results in impaired immune function. This review discusses recent new insights of the role of WASp at molecular and cellular level and evaluates how WASp deficiency affects important immunological features and how defective immune cell function contributes to compromised host defence