A1
Project A1 seeks to unravel the role of innate immune receptors in different mouse models of CNS injury, including sterile meningitis, stroke, a model of axonal degeneration and an Alzheimer's disease model. A1 is based on the assumption that - besides infectious ligands of innate immune receptors such as Toll-like receptors (TLRs) - endogenous ligands derived from CNS cells can induce innate immune actions.
A3
Project A3 will test the premise that neuroinflammation on the cellular level is an essential component of the regenerative long-term response of the brain to ischemia. Building on the results of the first funding period, A3 will elucidate the differential effects of monocytic cells and of the factors produced by these cells both in the periphery and in the brain on the acute and chronic phases after focal stroke. Using bone marrow chimeric mice and microglia ablation in the brain in vivo (CD11b-HSVTK transgenic mice), A3 will dissect the relative contribution of brain resident microglia versus haematogenous macrophages on key aspects of stroke pathogenesis, including cytokine production and secondary neurodegeneration.
A4
Project A4 will characterize the responsiveness of microglial cells for neurotransmitters and neurohormones in the normal and in the diseased brain. Using novel mouse lines, they plan to extend their in vitro studies from the first funding period, which included also acute brain slices, to the in vivo situation. Furthermore, they will test whether activation of receptors to neurotransmitters and neurohormones affect microglial function such as migration, phagocytosis or cytokine release, both under pathological and physiological conditions.
A5
Project A5 follows the assumption that microglia do not comprise a uniform cell type and that - even among a circumscribed population - microglia subsets differ by functional capacities. Based on the findings of the first funding period, A5 focuses on the degree of diversity and on the characteristics of responder subtypes of microglia. They aim to prove that either fixed (pre-destined) or still flexible (omnipotent) phenotypic orientations for defined subpopulations upon diverse challenges in vitro and in vivo exist. A5 will thus help to elucidate whether a putative assignment to discrete microglial subsets and reaction patterns in infection, injury and tissue repair exist, and if and / or how these subsets can be modulated.
A6
Project A6 aims to understand, by exchanging microglia with bone-marrow derived macrophages in a mouse model mimicking aspects of Alzheimer's disease (AD), whether peripherally recruited myeloid cells, in contrast to resident microglia, are capable to restrict Aβ burden. A second line of investigation aims to dissect the mechanistic underpinnings of interleukin (IL)-12- and / or IL-23-mediated β-amyloid reduction. The latter project is based on recent findings by A6 that genetic deficiency of IL-12 and / or IL-23 results in significantly reduced Aβ levels in AD mice. Finally, A6 will continue its studies on unraveling the mechanism of Aβ vaccination, i.e whether anti-Aβ antibodies in the context of Aβ vaccination exert their action outside or inside the brain. To this effect, A6 will utilize transgenic mice with an exclusive production of soluble and / or membrane bound anti-Aβ IgM antibodies, which were successfully generated during the first funding period.
A7
Project A7 seeks to differentiate the roles of resident microglia from other myeloid cells in the brain. The group will use diphtheria toxin receptor-based microglia/myeloid depletion models to study the consequences of microglia and macrophage deficiency for neuronal function in the brain. This approach complements and extends the CD11b-HSVTK-based microglia depletion strategy used by other members of the SFB TRR 43. By selectively ablating microglia versus peripheral myeloid cells, A7 aims to clarify the differential functions of microglia and other innate immune cells in acute and chronic neuroinflammatory conditions, including cerebral ischemia, axotomy, experimental autoimmune encephalomyelitis and models of neurodegenerative diseases.
A9
Project A9 aims to identify the mechanism of the cytokine interleukin (IL)-1β in Amyotrophic Lateral Sclerosis caused by mutations in the superoxide dismutase gene (SOD). Based on previous findings, A9 proposes that mutant (mt)SOD1 serves as both the first and the second stimulus for inflammasome activation in ALS. A9 will test the hypothesis that innate immune molecules sense the mtSOD1, eventually leading to an IL-1β release, which is NALP3-independent and therefore different from the mechanisms proposed for inflammasome activation by amyloid beta or islet amyloid polypeptide. A9 will use in vitro biochemical analyses and will generate transgenic animals to test its hypotheses.
A10
Project A10 focuses on a potential connection between a specialized membrane degradation system and the pathogenesis of an autoimmune disease. A10 will study how oligodendrocytes metabolize the myelin membrane and whether this occurs by outsourcing myelin membrane degradation to professional phagocytic cells such as microglia/macrophages. This hypothesis will be tested by employing transgenic mice, in which lysosomal degradation of microglia/macrophages is compromised. One major goal will be to find out whether the putative outsourcing of myelin degradation to microglia/macrophages predisposes an organism towards developing an anti-myelin autoimmune disease.
B5
Project B5 continues to analyze the role of the peripheral immune cells for stroke outcome. They will investigate the impact of post-stroke infections on phenotype and function of brain-infiltrating leukocytes in relation to processes of tissue regeneration and functional outcome. Particularly, it will be determined whether infections influence the phenotype, function and migratory behaviour of CNS-specific T cells resulting in destructive effects on post-ischemic angiogenesis, neurogenesis and functional recovery.
B6
Project B6 will address the longstanding question to what extent Multiple sclerosis (MS) is a primary autoimmune disease associated with secondary neurodegeneration, or a neurodegenerative disease with an unusual degree of secondary autoimmunity. To do so, B6 will utilize novel mouse mutants developing myelin disease and axonal degeneration, in which 'secondary' inflammation includes microglia/macrophages activation and the invasion of clonally expanded T cells. By establishing T cell clones from the brain, the properties of these T cells will be studied, ideally resulting in the identification of their target specificity. At the level of microglia/macrophages by the use and generation of novel transgenic mice, B6 will explore the role of endogenous erythropoietin (EPO) - and EPO receptor (EPOR)-mediated signaling. The pharmacological application of erythropoietin, known to act as anti-inflammatory drug, could potentially act as a 'break' in a vicious cycle of neurodegeneration and neuroinflammation.
B7
Project B7 investigates the role of i-proteasomes in mouse models of Alzheimer's and Parkinson's disease (AD and PD, respectively). Based on previous, rather unexpected findings of this project, namely that AD mice harbour considerably increased i-proteasome levels while deficiency in the i-proteasome component LMP7 significantly decreases Aβ burden, B7 will explore the potential pathogenetic impact of other i-proteasome components and extend these studies accordingly to mouse models of PD. The role of i-proteasomes in modulating AD/PD-associated inflammatory processes will be studied at the level of cytokine expression, microglia activation, its association with oxidative stress, its consequences for aggregate formation and neuronal functions such as the UPS-associated regulation of neuronal long term potentiation (LTP) as well as by changes in cognition and behaviour.
B9
Project B9 aims to dissect the pathological substrates of disease progression in MS by focusing on mechanisms of neuroaxonal damage. Besides assessing the role of differential neurofilament phosphorylation for neuroaxonal vulnerability in inflammatory CNS disease, animal models mimicking specific features of the progressive disease phase will be devised. Taking into account the widespread involvement of the cortex in progressive disease, differences in blood-brain barrier composition and permeability between cortical grey and white matter as well as the cortical repair capacity will be investigated.
B10
Project B10 seeks to find out which signals determine the migratory behavior of pathogenic T cells during the preclinical phase of transfer EAE in the Lewis rat. To this end real time intravital imaging analyses and functional characterizations will be carried out on encephalitogenic T cells in the preclinical EAE phase. Collaboration will include intravital two photon microscopy (2-PM) technology with A7 (Priller) and B6 (Nave/Ehrenreich). An additional aim of B10 is to discover the milieu and region(s) where pathogenic T cells get re-programmed, and to dissect the molecular factors determining the migratory capacity of T cells to enter the CNS. Interesting candidate genes possibly characterizing the encephalitogenic potential of T cells will be functionally tested.
B11
Project B11 aims to analyze in real time the activation and function of autoreactive T cells and B cells during chronic experimental autoimmune encephalomyelitis in C57BL/6 mice. To this purpose, 2-PM technology will be combined with molecular analyses to study the fluorescently tagged autoaggressive immune cell populations during the initiation phase in the secondary immune organs and during the established disease within acute and chronic CNS lesions. Mouse models are established that enable tracking of fluorescently labeled MOG-specific T and B cells.
B12
Project B12 will delineate the pathophysiology of secondary brain injury following subarachnoid hemorrhage (SAH). Specifically, B12 seeks to understand the relevance of and mechanisms leading to a spreading intracerebral immune response and subsequent delayed neuronal damage after SAH. B12 focuses on (i) the homing of circulating immune cells to the CNS perivascular space, (ii) the activation of resident CNS immune cells, as well as (iii) the interplay of activated/recruited immune cells with the neuroaxonal unit.
B13
Project B13 will address the role of CD8+ T cells in a rat model of relapsing-remitting MS using novel knock-out and transgenic rat strains. It will be tested whether CD8+ T cells fulfill a disease-promoting or a regulatory function by employing immunological techniques, histology and 2-PM microscopy. A central question will be whether CD8+ T cells are clonally expanded in CNS infiltrates, and attempts will be made to determine the specific antigens they recognize. The hypothesis that antigen-specific CD8+ T cells contribute to CNS inflammation and damage in neuroinflammatory diseases will be challenged by generating T cell receptor transgenic rat lines.