Dominik Hartl

Granulocytic myeloid derived suppressor cells expand in human pregnancy and modulate T-cell responses

Immune tolerance toward the semiallogeneic fetus plays a crucial role in the maintenance of pregnancy. Myeloid‐derived suppressor cells (MDSCs) are innate immune cells characterized by their ability to modulate T‐cell responses. Recently, we showed that MDSCs accumulate in cord blood of healthy newborns, yet their role in materno–fetal tolerance remained elusive. In the present study, we demonstrate that MDSCs with a granulocytic phenotype (GR‐MDSCs) are highly increased in the peripheral blood of healthy pregnant women during all stages of pregnancy compared with nonpregnant controls, whereas numbers of monocytic MDSCs were unchanged. GR‐MDSCs expressed the effector enzymes arginase‐I and iNOS, produced high amounts of ROS and efficiently suppressed T‐cell proliferation. After parturition, GR‐MDSCs decreased within a few days. In combination, our results show that GR‐MDSCs expand in normal human pregnancy and may indicate a role for MDSCs in materno–fetal tolerance.

Granulocytic Myeloid-Derived Suppressor Cells Accumulate in Human Placenta and Polarize toward a Th2 Phenotype

Tolerance induction toward the semiallogeneic fetus is crucial to enable a successful pregnancy; its failure is associated with abortion or preterm delivery. Skewing T cell differentiation toward a Th2-dominated phenotype seems to be pivotal in maternal immune adaption, yet underlying mechanisms are incompletely understood. Myeloid-derived suppressor cells (MDSCs) are innate immune cells that mediate T cell suppression and are increased in cord blood of healthy newborns and in peripheral blood of pregnant women. In this study, we demonstrate that granulocytic MDSCs (GR-MDSCs) accumulate in human placenta of healthy pregnancies but are diminished in patients with spontaneous abortions. Placental GR-MDSCs effectively suppressed T cell responses by expression of arginase I and production of reactive oxygen species and were activated at the maternal–fetal interface through interaction with trophoblast cells. Furthermore, GR-MDSCs isolated from placenta polarized CD4+ T cells toward a Th2 cytokine response. These results highlight a potential role of GR-MDSCs in inducing and maintaining maternal–fetal tolerance and suggest them as a promising target for therapeutic manipulation of pregnancy complications.

Influenza A(H1N1)pdm09 and Cystic Fibrosis Lung Disease: A Systematic Meta-Analysis

Background To systematically assess the literature published on the clinical impact of Influenza A(H1N1)pdm09 on cystic fibrosis (CF) patients. Methods An online search in PUBMED database was conducted. Original articles on CF patients with Influenza A(H1N1)pdm09 infection were included. We analyzed incidence, symptoms, clinical course and treatment. Results Four surveys with a total of 202 CF patients infected by Influenza A(H1N1)pdm09 were included. The meta-analysis showed that hospitalisation rates were higher in CF patients compared to the general population. While general disease symptoms were comparable, the clinical course was more severe and case fatality rate (CFR) was higher in CF patients compared to asthmatics and the general population. Conclusions Evidence so far suggests that CF patients infected with Influenza A(H1N1)pdm09 show increased morbidity and a higher CFR compared to patients with other chronic respiratory diseases and healthy controls. Particularly, CF patients with advanced stage disease seem to be more susceptible to severe lung disease. Accordingly, early antiviral and antibiotic treatment strategies are essential in CF patients. Preventive measures, including vaccination as well as hygiene measures during the influenza season, should be reinforced and improved in CF patients.

Characterization of rapid neutrophil extracellular trap formation and its cooperation with phagocytosis in human neutrophils

Neutrophils, as the first cellular line of innate host defense, employ phagocytosis and formation of neutrophil extracellular traps (NETs) to combat infections. Classical NET formation induced by phorbol myristate acetate requires several hours to complete. However, recent studies demonstrated rapid NET formation in neutrophils upon stimulation by platelets, Staphylococcus aureus or fungal products. Here we describe that antibody- or complement-induced phagocytosis triggers rapid NET formation. In contrast to classical NETosis, chemical inhibition of NADPH oxidase as well as using NADPH oxidase-deficient patient neutrophils did not affect rapid NET formation. Although phagocytosis and rapid NET formation may not be the prerequisite of each other, cooperation of phagocytosis and rapid NET formation may be essential to improve the efficiency of defense mechanisms in combating disseminating bacteria. Dissecting the differential mechanisms of NET formation is crucial to develop novel therapeutic strategies for infectious and auto-immune diseases where NETs play an essential role.

In vivo hypoxia PET imaging quantifies the severity of arthritic joint inflammation in line with overexpression of HIF and enhanced ROS generation

Hypoxia is essential for the development of autoimmune diseases such as rheumatoid arthritis (RA) and is associated with the expression of reactive oxygen species (ROS), because of the enhanced infiltration of immune cells. The aim of this study was to demonstrate the feasibility of measuring hypoxia noninvasively in vivo in arthritic ankles with PET/MRI using the hypoxia tracers 18F-fluoromisonidazole (18F-FMISO) and 18F-fluoroazomycinarabinoside (18F-FAZA). Additionally, we quantified the temporal dynamics of hypoxia and ROS stress using L-012, an ROS-sensitive chemiluminescence optical imaging probe, and analyzed the expression of hypoxia-inducible factors (HIFs). Methods: Mice underwent noninvasive in vivo PET/MRI to measure hypoxia or optical imaging to analyze ROS expression. Additionally, we performed ex vivo pimonidazole-/HIF-1α immunohistochemistry and HIF-1α/2α Western blot/messenger RNA analysis of inflamed and healthy ankles to confirm our in vivo results. Results: Mice diseased from experimental RA exhibited a 3-fold enhancement in hypoxia tracer uptake, even in the early disease stages, and a 45-fold elevation in ROS expression in inflamed ankles compared with the ankles of healthy controls. We further found strong correlations of our noninvasive in vivo hypoxia PET data with pimonidazole and expression of HIF-1α in arthritic ankles. The strongest hypoxia tracer uptake was observed as soon as day 3, whereas the most pronounced ROS stress was evident on day 6 after the onset of experimental RA, indicating that tissue hypoxia can precede ROS stress in RA. Conclusion: Collectively, for the first time to our knowledge, we have demonstrated that the noninvasive measurement of hypoxia in inflammation using 18F-FAZA and 18F-FMISO PET imaging represents a promising new tool for uncovering and monitoring rheumatic inflammation in vivo. Further, because hypoxic inflamed tissues are associated with the overexpression of HIFs, specific inhibition of HIFs might represent a new powerful treatment strategy.

Aktuelle Ansätze und Kontroversen zu angeborener Immunität und Lungenerkrankung bei zystischer Fibrose

Die Lungenerkrankung bei zystischer Fibrose (CF) ist gekennzeichnet durch chronische Infektion und Inflammation. Bei der entzündlichen Reaktion im Rahmen der CF steht die Aktivierung des angeborenen Immunsystems im Vordergrund. Bakterien und Pilze sind die wichtigsten Krankheitserreger, die bei CF chronisch die Atemwege besiedeln. In Reaktion auf die mikrobiologische Bedrohung, die von speziellen Rezeptoren des angeborenen Immunsystems auf Atemwegsepithelzellen und myeloischen Zellen erkannt wird, werden chemische Lockstoffe ausgeschüttet, die neutrophile Granulozyten in großer Zahl in die von CF betroffenen Atemwege rekrutieren. Den Neutrophilen gelingt es jedoch nicht, die invasiven Krankheitserreger wirksam zu eliminieren; stattdessen setzen sie schädigende Proteasen und Oxidanzien frei und verursachen letztlich Gewebeschäden. Mit diesem Beitrag liefern wir eine Zusammenfassung und Übersicht zu aktuellen Ansätzen und Kontroversen zum Thema der angeborenen Immunität bei CF-Lungenerkrankung und gehen dabei insbesondere auf die ungeklärten Fragen ein, ob die Inflammation bei CF positiv oder negativ ist und wie die Mechanismen der angeborenen Immunität therapeutisch genutzt werden könnten. Übersetzung aus J Innate Immun 2016;8:531-540 (DOI: 10.1159/000446840)

A functional inflammasome activation assaydifferentiates patients with pathogenic NLRP3mutations and symptomatic patients with lowpenetrance variants

Cryopyrin-associated periodic syndromes (CAPS) are characterized by recurrent episodes of systemic inflammation caused by mutations in the NLRP3 gene. Besides confirmed pathogenic NLRP3 mutations, patients with CAPS-like symptoms frequently show low penetrance variants in NLRP3. The disease relevance of these variants is inconsistent. In this study, we investigated if an inflammasome activation assay differentiates between patients with confirmed pathogenic CAPS mutations, patients with low penetrance NLRP3 variants (V198M and Q703K) and healthy controls. The release of mature IL-1β, IL-18, and caspase-1 into cell culture supernatants after 4h of inflammasome stimulation was significantly increased in patients with confirmed pathogenic CAPS mutations compared to low penetrance NLRP3 variants and controls. IL-1β secretion in CAPS patients correlated with disease severity. This inflammasome activation assay differentiates between autoinflammation patients with confirmed pathogenic CAPS mutations and patients with low penetrance NLRP3 variants, and points towards alternative pathophysiological mechanisms in low penetrance NLRP3 variants.

A functional inflammasome activation assay discriminates between genetically proven caps patients and patients with low penetrance NLRP3 variants

The cryopyrin-associated periodic syndromes (CAPS) are characterized by recurrent episodes of systemic inflammation. CAPS is caused by mutations in the NLRP3 gene encoding cryopyrin, an important component of the NLRP3 inflammasome that activates caspase-1 resulting in inflammation by excessive production of IL-1β and others. A diagnostic dilemma is often encountered in patients with unspecific inflammatory symptoms like fatigue, muscle pain, arthralgia or slight hearing loss and low penetrance variants in NLRP3 / CIAS with an inconsistent clinical phenotype. The analysis of IL-1β in the serum did not prove to be a valid diagnostic test in these individuals.