To explore the initial steps by which transplanted mesenchymal stem cells (MSCs) interact with the vessel wall in the course of extravasation, we studied binding of human MSCs to endothelial cells (ECs). In a parallel plate flow chamber, MSCs bound to human umbilical vein ECs (HUVECs) similar to peripheral-blood mononuclear cells (PBMCs) or CD34 ؉ hematopoietic progenitors at shear stresses of up to 2 dynes/cm 2 . This involved rapid extension of podia, rolling, and subsequent firm adhesion that was increased when ECs were prestimulated with TNF-␣. MSC binding was suppressed when ECs were pretreated with function-blocking anti-P-selectin antibody, and rolling of MSCs was induced on immobilized P-selectin, indicating that P-selectin was involved in this process. IntroductionIn recent years, mesenchymal stem cells (MSCs) have been characterized as adherent-cell populations originating from bone marrow, capable of expanding in vitro as undifferentiated cells or differentiating into osteocytes, chondrocytes, tenocytes, adipocytes, or smooth muscle cells. [1][2][3] MSCs have been used in a number of preclinical models to mediate the regeneration of muscle, endothelial, neuronal, skin, or renal epithelial tissue. [4][5][6][7] In vitro differentiation studies have demonstrated the potential of MSCs to also form alveolar and airway epithelial cells or cardiac pacemaker cells. 8,9 Moreover, MSCs have been transplanted intravenously and shown to distribute to spleen, bone, lung, and cartilage in several rodent models. [10][11][12] Intravenously injected MSCs have already been used in patients to accelerate hematopoietic reconstitution after hematopoietic stem cell transplantation, to overcome the molecular defect in children with osteogenesis imperfecta, or to alleviate the outcome after myocardial infarction. [13][14][15][16][17] Transplantation experiments in mice and primates have shown that intravenously applied MSCs distribute to several tissues and may accumulate in the lungs. 10,12,18,19 However, currently it is poorly understood to what degree MSCs use specific adhesion mechanisms for egress from the bloodstream and whether they home in a tissue-specific manner. To leave the bloodstream, mature leukocytes and hematopoietic progenitor cells (HPCs) have been shown to undergo a coordinated sequence of adhesion steps, initiated by tethering events, which are mainly mediated by selectins and their ligands. 20,21 Subsequently, the captured cells roll and encounter chemokines, which eventually activate integrins, resulting in firm arrest and subsequent transendothelial migration.To elucidate the potential of MSCs to undergo coordinated steps of interaction with endothelial cells (ECs), we investigated human MSCs under shear flow using a parallel plate flow chamber and by intravital microscopy in mice. We show here that human MSCs home to different tissues and display coordinated rolling and adhesion behavior on ECs. Although P-selectin glycoprotein ligand 1 (PSGL-1) is not expressed by MSCs, MSCs bind to ECs in a P-sele...

Complement is an ancient danger-sensing system that contributes to host defense, immune surveillance and homeostasis. C5a and its G protein–coupled receptor mediate many of the proinflammatory properties of complement. Despite the key role of C5a in allergic asthma, autoimmune arthritis, sepsis and cancer, knowledge about its regulation is limited. Here we demonstrate that IgG1 immune complexes (ICs), the inhibitory IgG receptor FcγRIIB and the C-type lectin–like receptor dectin-1 suppress C5a receptor (C5aR) functions. IgG1 ICs promote the association of FcγRIIB with dectin-1, resulting in phosphorylation of Src homology 2 domain–containing inositol phosphatase (SHIP) downstream of FcγRIIB and spleen tyrosine kinase downstream of dectin-1. This pathway blocks C5aR-mediated ERK1/2 phosphorylation, C5a effector functions in vitro and C5a-dependent inflammatory responses in vivo, including peritonitis and skin blisters in experimental epidermolysis bullosa acquisita. Notably, high galactosylation of IgG N-glycans is crucial for this inhibitory property of IgG1 ICs, as it promotes the association between FcγRIIB and dectin-1. Thus, galactosylated IgG1 and FcγRIIB exert anti-inflammatory properties beyond their impact on activating FcγRs.

Autoantibodies are frequently observed in healthy individuals. In a minority of these individuals, they lead to manifestation of autoimmune diseases, such as rheumatoid arthritis or Graves' disease. Overall, more than 2.5% of the population is affected by autoantibody-driven autoimmune disease. Pathways leading to autoantibody-induced pathology greatly differ among different diseases, and autoantibodies directed against the same antigen, depending on the targeted epitope, can have diverse effects. To foster knowledge in autoantibody-induced pathology and to encourage development of urgently needed novel therapeutic strategies, we here categorized autoantibodies according to their effects. According to our algorithm, autoantibodies can be classified into the following categories: (1) mimic receptor stimulation, (2) blocking of neural transmission, (3) induction of altered signaling, triggering uncontrolled (4) microthrombosis, (5) cell lysis, (6) neutrophil activation, and (7) induction of inflammation. These mechanisms in relation to disease, as well as principles of autoantibody generation and detection, are reviewed herein.

Background Psoriasis is a chronic inflammatory skin disorder affecting about 2% of white-skinned individuals. Epidemiological data on the prevalence and degree of coronary artery calcification (CAC) as an indicator for cardiovascular diseases in patients with psoriasis are contradictory. Objectives To study the prevalence and degree of CAC as an indicator for cardiovascular diseases in 32 patients with psoriasis matched for age, sex and risk factors to an equally sized control population. Methods Noncontrast-enhanced 16-row spiral computed tomography was performed in patients and controls. Results We found a significantly increased prevalence (59AE4% vs. 28AE1%, P ¼ 0AE015) and severity (CAC score according to Agatston 3AE7 vs. 0AE0, P ¼ 0AE019) of CAC in patients with psoriasis. Multiple linear regression calculations identified psoriasis as a likely independent risk factor for CAC. Conclusions Our results point towards the potentially systemic nature of the inflammatory processes underlying the pathogenesis of psoriasis, which may therefore be considered a potentially severe systemic disease.

Background Pemphigus encompasses a group of life‐threatening autoimmune bullous diseases characterized by blisters and erosions of the mucous membranes and skin. Before the era of immunosuppressive treatment, pemphigus was almost always fatal. Due to its rarity, only few randomized controlled therapeutic trials are available. Recently, rituximab has been approved as first‐line treatment for moderate and severe pemphigus vulgaris in Europe and the United States. Objectives The Autoimmune blistering diseases Task Force of the European Academy of Dermatology and Venereology (EADV) has initiated a throughout update of the guideline for the management of patients with pemphigus. Results The guidelines for the management of pemphigus were updated, and the degree of consent among all task force members was included. The final version of the guideline was consented by the European Dermatology Forum (EDF) and several patient organizations.

Taken together, several measurements indicative of insulin resistance were found to be significantly correlated with the PASI score. The concept of insulin resistance as a consequence of chronic inflammation and possible pathogenetic cause for comorbidities known to be associated with psoriasis is supported by these data. Our findings validate further studies on larger cohorts as well as interventional studies.

Spontaneous and experimental metastasis can be effectively inhibited by the widely used anticoagulant heparin in different tumor models. At the cellular level, many of the antimetastatic effects of heparin in vivo are due to its action on P-selectin-mediated binding. Whereas previous attention has focused on P-selectin-dependent tumor-cell-platelet interactions in blood-borne metastasis, we sought to address the potential contribution of endothelial P-selectin expression to adhesive events between the microvasculature and melanoma cells in vivo. Transplantation of bone marrow from P-selectin-deficient into wild-type mice conveyed inhibition of experimental melanoma metastasis. However, the extent to which bone marrow-conferred lack of platelet P-selectin expression attenuated melanoma lung metastasis was significantly less than that seen in P-selectindeficient mice, suggesting that endothelial P-selectin expression may additionally contribute to formation of hematogenous metastases. This assumption was supported by our intravital microscopy studies, in which a significant proportion of melanoma cells were capable of directly interacting with postcapillary venules of the murine ear in a P-selectin-dependent manner. Heparin not only inhibits P-selectin-mediated melanoma cell rolling but also attenuates melanoma metastasis formation in vivo, further supporting the concept that endothelial P-selectin expression may represent an additional target of heparin action in experimental melanoma lung metastasis.

Epidermolysis bullosa acquisita (EBA) is an orphan autoimmune disease. Patients with EBA suffer from chronic inflammation as well as blistering and scarring of the skin and mucous membranes. Current treatment options rely on non-specific immunosuppression, which in many cases, does not lead to a remission of treatment. Hence, novel treatment options are urgently needed for the care of EBA patients. During the past decade, decisive clinical observations, and frequent use of pre-clinical model systems have tremendously increased our understanding of EBA pathogenesis. Herein, we review all of the aspects of EBA, starting with a detailed description of epidemiology, clinical presentation, diagnosis, and current treatment options. Of note, pattern analysis via direct immunofluorescence microscopy of a perilesional skin lesion and novel serological test systems have significantly facilitated diagnosis of the disease. Next, a state-of the art review of the current understanding of EBA pathogenesis, emerging treatments and future perspectives is provided. Based on pre-clinical model systems, cytokines and kinases are among the most promising therapeutic targets, whereas high doses of IgG (IVIG) and the anti-CD20 antibody rituximab are among the most promising “established” EBA therapeutics. We also aim to raise awareness of EBA, as well as initiate basic and clinical research in this field, to further improve the already improved but still unsatisfactory conditions for those diagnosed with this condition.