Neuronal hyperactivity recruits microglial processes via neuronal NMDA receptors and microglial P2Y12 receptors after status epilepticus

Microglia: Dynamic Mediators of Synapse Development and Plasticity

Neuronal communication underlies all brain activity and the genesis of complex behavior. Emerging research has revealed an unexpected role for immune molecules in the development and plasticity of neuronal synapses. Moreover microglia, the resident immune cells of the brain, express and secrete immune-related signaling molecules that alter synaptic transmission and plasticity in the absence of inflammation. When inflammation does occur, microglia modify synaptic connections and synaptic plasticity required for learning and memory. Here we review recent findings demonstrating how the dynamic interactions between neurons and microglia shape the circuitry of the nervous system in the healthy brain and how altered neuron-microglia signaling could contribute to disease.

N-Palmitoylethanolamine Prevents the Run-down of Amplitudes in Cortical Spreading Depression Possibly Implicating Proinflammatory Cytokine Release

Cortical spreading depression (CSD), a wave of neuronal depolarization in the cerebral cortex following traumatic brain injury or cerebral ischemia, significantly aggravates brain damage. Here, we tested whether N-palmitoylethanolamine (PEA), a substance that effectively reduces lesion volumes and neurological deficits after ischemic stroke, influences CSD. CSD was elicited chemically in adult rats and occurrence, amplitude, duration and propagation velocity of CSD was determined prior to and for 6 hours after intraperitoneal injection of PEA. The chosen systemic administration of PEA stabilized the amplitude of CSD for at least four hours and prevented the run-down of amplitudes that is typically observed and was also seen in untreated controls. The propagation velocity of the CSD waves was unaltered indicating stable neuronal excitability. The stabilization of CSD amplitudes by PEA indicates that inhibition or prevention of CSD does not underlie PEA's profound neuroprotective effect. Rather, PEA likely inhibits proinflammatory cytokine release thereby preventing the run-down of CSD amplitudes. This contribution of PEA to the maintenance of neuronal excitability in healthy tissue during CSD potentially adds to neuroprotection outside a damaged area, while other mechanisms control PEA-mediated neuroprotection in damaged tissue resulting from traumatic brain injury or cerebral ischemia.

Microglial P2Y12 is necessary for synaptic plasticity in mouse visual cortex

Microglia are the resident immune cells of the brain. Increasingly, they are recognized as important mediators of normal neurophysiology, particularly during early development. Here we demonstrate that microglia are critical for ocular dominance plasticity. During the visual critical period, closure of one eye elicits changes in the structure and function of connections underlying binocular responses of neurons in the visual cortex. We find that microglia respond to monocular deprivation during the critical period, altering their morphology, motility and phagocytic behaviour as well as interactions with synapses. To explore the underlying mechanism, we focused on the P2Y12 purinergic receptor, which is selectively expressed in non-activated microglia and mediates process motility during early injury responses. We find that disrupting this receptor alters the microglial response to monocular deprivation and abrogates ocular dominance plasticity. These results suggest that microglia actively contribute to experience-dependent plasticity in the adolescent brain.

Microglia play key roles during early neurodevelopment. Here the authors show that microglia are important mediators of ocular dominance plasticity (ODP). Microglia respond to monocular deprivation during the visual critical period, and disrupting microglial P2Y12 purinergic receptor abrogates ODP.

Proteomic profiling of epileptogenesis in a rat model: Focus on inflammation

Detailed knowledge about the patterns of molecular alterations during epileptogenesis is a presupposition for identifying targets for preventive or disease-modifying approaches, as well as biomarkers of the disease. Large-scale differential proteome analysis can provide unique and novel perspectives based on comprehensive data sets informing about the complex regulation patterns in the disease proteome. Thus, we have completed an elaborate differential proteome analysis based on label-free LC-MS/MS in a rat model of epileptogenesis. Hippocampus and parahippocampal cortex tissues were sampled and analyzed separately at three key time points chosen for monitoring disease development following electrically-induced status epilepticus, namely, the early post-insult phase, the latency phase, and the chronic phase with spontaneous recurrent seizures. We focused the bioinformatics analysis on proteins linked to immune and inflammatory responses, because of the emerging evidence of the specific pathogenic role of inflammatory signalings during epileptogenesis. In the early post-insult and the latency phases, pathway enrichment analysis revealed an extensive over-representation of Toll-like receptor signaling, pro-inflammatory cytokines, heat shock protein regulation, and transforming growth factor beta signaling and leukocyte transendothelial migration. The inflammatory response in the chronic phase proved to be more moderate with differential expression in the parahippocampal cortex exceeding that in the hippocampus. The data sets provide novel information about numerous differentially expressed proteins, which serve as interaction partners or modulators in key disease-associated inflammatory signaling events. Noteworthy, a set of proteins which act as modulators of the ictogenic Toll-like receptor signaling proved to be differentially expressed. In addition, we report novel data demonstrating the regulation of different Toll-like receptor ligands during epileptogenesis. Taken together, the findings deepen our understanding of modulation of inflammatory signaling during epileptogenesis providing an excellent and comprehensive basis for the identification of target and biomarker candidates.

Subsequent Bilateral Hippocampal Diffusion Restriction and Atrophy in Repeated Status Epilepticus

BACKGROUND

Cortical lesions in status epilepticus have been reported but the underlying mechanisms are poorly elucidated.

CASE SUMMARY

We report on afemale patient (75 years) with a history of alcohol abuse who presented with complex partial status epilepticus and lateralized epileptiform discharges in the left frontal and temporal regions in EEG. While cranial magnetic resonance imaging (MRI) showed left hippocampal T2-hyperintensity and diffusion restriction, cerebrospinal fluid was normal and revealed no limbic encephalitis-related antibodies. Following treatment with levitiracetam, seizures ceased and the patient was dismissed. Nine months later, she was readmitted with generalized status epilepticus. Cranial MI now showed hippocampal diffusion restriction and T2 hyperintensity, but in the right hemisphere, as well as atrophy and partial gliotic transformation of the initially affected left hippocampus.

DISCUSSION

Although hippocampal damage due to antibody-negative limbic encephalitis cannot be ruled out, our observation of subsequent bilateral hippocampal diffusion restriction with gliotic transformation may demonstrate permanent seizure-induced structural brain damage and underlines the importance of further research to elucidate the effects of prolonged epileptic discharges on cerebral structural integrity.

Deciphering Resting Microglial Morphology and Process Motility from a Synaptic Prospect

Microglia, the resident immune cells of the central nervous system (CNS), were traditionally believed to be set into action only in case of injury or disease. Accordingly, microglia were assumed to be inactive or resting in the healthy brain. However, recent studies revealed that microglia carry out active tissue sampling in the intact brain by extending and retracting their ramified processes while periodically contacting synapses. Microglial morphology and motility as well as the frequency and duration of physical contacts with synaptic elements were found to be modulated by neuronal activity, sensory experience and neurotransmission; however findings have not been straightforward. Microglial cells are the most morphologically plastic element of the CNS. This unique feature confers them the possibility to locally sense activity, and to respond adequately by establishing synaptic contacts to regulate synaptic inputs by the secretion of signaling molecules. Indeed, microglial cells can hold new roles as critical players in maintaining brain homeostasis and regulating synaptic number, maturation and plasticity. For this reason, a better characterization of microglial cells and cues mediating neuron-to-microglia communication under physiological conditions may help advance our understanding of the microglial behavior and its regulation in the healthy brain. This review highlights recent findings on the instructive role of neuronal activity on microglial motility and microglia-synapse interactions, focusing on the main transmitters involved in this communication and including newly described communication at the tripartite synapse.

Activation of microglial P2Y12 receptor is required for outward potassium currents in response to neuronal injury

Microglia, the resident immune cells in the central nervous system (CNS), constantly survey the surrounding neural parenchyma and promptly respond to brain injury. Activation of purinergic receptors such as P2Y12 receptors (P2Y12R) in microglia has been implicated in chemotaxis toward ATP that is released by injured neurons and astrocytes. Activation of microglial P2Y12R elicits outward potassium current that is associated with microglial chemotaxis in response to injury. This study aimed at investigating the identity of the potassium channel implicated in microglial P2Y12R-mediated chemotaxis following neuronal injury and understanding the purinergic signaling pathway coupled to the channel. Using a combination of two-photon imaging, electrophysiology and genetic tools, we found the ATP-induced outward current to be largely dependent on P2Y12R activation and mediated by G-proteins. Similarly, P2Y12R-coupled outward current was also evoked in response to laser-induced single neuron injury. This current was abolished in microglia obtained from mice lacking P2Y12R. Dissecting the properties of the P2Y12R-mediated current using a pharmacological approach revealed that both the ATP and neuronal injury-induced outward current in microglia was sensitive to quinine (1mM) and bupivacaine (400μM), but not tetraethylammonium (TEA) (10mM) and 4-aminopyridine (4-AP) (5mM). These results suggest that the quinine/bupivacaine-sensitive potassium channels are the functional effectors of the P2Y12R-mediated signaling in microglia activation following neuronal injury.

ATPergic signalling during seizures and epilepsy

Much progress has been made over the last few decades in the identification of new anti-epileptic drugs (AEDs). However, 30% of epilepsy patients suffer poor seizure control. This underscores the need to identify alternative druggable neurotransmitter systems and drugs with novel mechanisms of action. An emerging concept is that seizure generation involves a complex interplay between neurons and glial cells at the tripartite synapse and neuroinflammation has been proposed as one of the main drivers of epileptogenesis. The ATP-gated purinergic receptor family is expressed throughout the brain and is functional on neurons and glial cells. ATP is released in high amounts into the extracellular space after increased neuronal activity and during chronic inflammation and cell death to act as a neuro- and gliotransmitter. Emerging work shows pharmacological targeting of ATP-gated purinergic P2 receptors can potently modulate seizure generation, inflammatory processes and seizure-induced brain damage. To date, work showing the functional contribution of P2 receptors has been mainly performed in animal models of acute seizures, in particular, by targeting the ionotropic P2X7 receptor subtype. Other ionotropic P2X and metabotropic P2Y receptor family members have also been implicated in pathological processes following seizures such as the P2X4 receptor and the P2Y12 receptor. However, during epilepsy, the characterization of P2 receptors was mostly restricted to the study of expressional changes of the different receptor subtypes. This review summarizes the work to date on ATP-mediated signalling during seizures and the functional impact of targeting the ATP-gated purinergic receptors on seizures and seizure-induced pathology. This article is part of the Special Issue entitled 'Purines in Neurodegeneration and Neuroregeneration'.

Altered morphological dynamics of activated microglia after induction of status epilepticus

BACKGROUND

Microglia cells are the resident macrophages of the central nervous system and are considered its first line of defense. In the normal brain, their ramified processes are highly motile, constantly scanning the surrounding brain tissue and rapidly moving towards sites of acute injury or danger signals. These microglial dynamics are thought to be critical for brain homeostasis. Under pathological conditions, microglial cells undergo "activation," which modifies many of their molecular and morphological properties. Investigations of the effects of activation on motility are limited and have given mixed results. In particular, little is known about how microglial motility is altered in epilepsy, which is characterized by a strong inflammatory reaction and microglial activation.

METHODS

We used a mouse model of status epilepticus induced by kainate injections and time-lapse two-photon microscopy to image GFP-labeled microglia in acute hippocampal brain slices. We studied how microglial activation affected the motility of microglial processes, including basal motility, and their responses to local triggering stimuli.

RESULTS

Our study reveals that microglial motility was largely preserved in kainate-treated animals, despite clear signs of microglial activation. In addition, whereas the velocities of microglial processes during basal scanning and towards a laser lesion were unaltered 48 h after status epilepticus, we observed an increase in the size of the territory scanned by single microglial processes during basal motility and an elevated directional velocity towards a pipette containing a purinergic agonist.

CONCLUSIONS

Microglial activation differentially impacted the dynamic scanning behavior of microglia in response to specific acute noxious stimuli, which may be an important feature of the adaptive behavior of microglia during pathophysiological conditions.

Distinct synaptic and neurochemical changes to the granule cell-CA3 projection in Bassoon mutant mice

Proper synaptic function depends on a finely-tuned balance between events such as protein synthesis and structural organization. In particular, the functional loss of just one synaptic-related protein can have a profound impact on overall neuronal network function. To this end, we used a mutant mouse model harboring a mutated form of the presynaptic scaffolding protein Bassoon (Bsn), which is phenotypically characterized by: (i) spontaneous generalized epileptic seizure activity, representing a chronically-imbalanced neuronal network; and (ii) a dramatic increase in hippocampal brain-derived neurotrophic factor (BDNF) protein concentration, a key player in synaptic plasticity. Detailed morphological and neurochemical analyses revealed that the increased BDNF levels are associated with: (i) modified neuropeptide distribution; (ii) perturbed expression of selected markers of synaptic activation or plasticity; (iii) subtle changes to microglial structure; and (iv) morphological alterations to the mossy fiber (MF) synapse. These findings emphasize the important contribution of Bassoon protein to normal hippocampal function, and further characterize the Bsn-mutant as a useful model for studying the effects of chronic changes to network activity.

Microglia processes associate with diffusely injured axons following mild traumatic brain injury in the micro pig

Background

Mild traumatic brain injury (mTBI) is an all too common occurrence that exacts significant personal and societal costs. The pathophysiology of mTBI is complex, with reports routinely correlating diffuse axonal injury (DAI) with prolonged morbidity. Progressive chronic neuroinflammation has also recently been correlated to morbidity, however, the potential association between neuroinflammatory microglia and DAI is not well understood. The majority of studies exploring neuroinflammatory responses to TBI have focused on more chronic phases of injury involving phagocytosis associated with Wallerian change. Little, however, is known regarding the neuroinflammatory response seen acutely following diffuse mTBI and its potential relationship to early DAI. Additionally, while inflammation is drastically different in rodents compared to humans, pigs and humans share very similar inflammatory profiles and responses.

Methods

In the current study, we employed a modified central fluid percussion model in micro pigs. Using this model of diffuse mTBI, paired with various immunohistological endpoints, we assessed the potential association between acute thalamic DAI and neuroinflammation 6 h following injury.

Results

Injured micro pigs displayed substantial axonal damage reflected in the presence of APP+ proximal axonal swellings, which were particularly prominent in the thalamus. In companion, the same thalamic sites displayed extensive neuroinflammation, which was observed using Iba-1 immunohistochemistry. The physical relationship between microglia and DAI, assessed via confocal 3D analysis, revealed a dramatic increase in the number of Iba-1+ microglial processes that contacted APP+ proximal axonal swellings compared to uninjured myelinated thalamic axons in sham animals.

Conclusions

In aggregate, these studies reveal acute microglial process convergence on proximal axonal swellings undergoing DAI, an interaction not previously recognized in the literature. These findings transform our understanding of acute neuroinflammation following mTBI and may suggest its potential as a diagnostic and/or a therapeutic target.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-015-0405-6) contains supplementary material, which is available to authorized users.

Purinergic mechanisms in neuroinflammation: An update from molecules to behavior

The principle functions of neuroinflammation are to limit tissue damage and promote tissue repair in response to pathogens or injury. While neuroinflammation has utility, pathophysiological inflammatory responses, to some extent, underlie almost all neuropathology. Understanding the mechanisms that control the three stages of inflammation (initiation, propagation and resolution) is therefore of critical importance for developing treatments for diseases of the central nervous system. The purinergic signaling system, involving adenosine, ATP and other purines, plus a host of P1 and P2 receptor subtypes, controls inflammatory responses in complex ways. Activation of the inflammasome, leading to release of pro-inflammatory cytokines, activation and migration of microglia and altered astroglial function are key regulators of the neuroinflammatory response. Here, we review the role of P1 and P2 receptors in mediating these processes and examine their contribution to disorders of the nervous system. Firstly, we give an overview of the concept of neuroinflammation. We then discuss the contribution of P2X, P2Y and P1 receptors to the underlying processes, including a discussion of cross-talk between these different pathways. Finally, we give an overview of the current understanding of purinergic contributions to neuroinflammation in the context of specific disorders of the central nervous system, with special emphasis on neuropsychiatric disorders, characterized by chronic low grade inflammation or maternal inflammation. An understanding of the important purinergic contribution to neuroinflammation underlying neuropathology is likely to be a necessary step towards the development of effective interventions. This article is part of the Special Issue entitled 'Purines in Neurodegeneration and Neuroregeneration'.

Activation of acid-sensing ion channels by localized proton transient reveals their role in proton signaling

Extracellular transients of pH alterations likely mediate signal transduction in the nervous system. Neuronal acid-sensing ion channels (ASICs) act as sensors for extracellular protons, but the mechanism underlying ASIC activation remains largely unknown. Here, we show that, following activation of a light-activated proton pump, Archaerhodopsin-3 (Arch), proton transients induced ASIC currents in both neurons and HEK293T cells co-expressing ASIC1a channels. Using chimera proteins that bridge Arch and ASIC1a by a glycine/serine linker, we found that successful coupling occurred within 15 nm distance. Furthermore, two-cell sniffer patch recording revealed that regulated release of protons through either Arch or voltage-gated proton channel Hv1 activated neighbouring cells expressing ASIC1a channels. Finally, computational modelling predicted the peak proton concentration at the intercellular interface to be at pH 6.7, which is acidic enough to activate ASICs in vivo. Our results highlight the pathophysiological role of proton signalling in the nervous system.

Fractalkine Signaling and Microglia Functions in the Developing Brain

Microglial cells are the resident macrophages of the central nervous system (CNS). Besides their classical roles in pathological conditions, these immune cells also dynamically interact with neurons and influence their structure and function in physiological conditions. The neuronal chemokine fractalkine and its microglial receptor CX3CR1 are one important signaling pathway involved in these reciprocal interactions. In the present review, we will discuss recent evidence indicating that fractalkine signaling also determines several functions of microglial cells during normal CNS development. It has been known for a decade that microglial cells influence the neuronal death that normally occurs during CNS development. Surprisingly, recent evidence indicates that they can also support survival of developing neurons, control axon outgrowth, and laminar positioning of subsets of interneurons in the forebrain. Moreover, microglial cells influence the maturation of synaptic circuits at early postnatal stages: their phagocytic activity allows them to eliminate inappropriate synapses and they can also influence the functional expression of synaptic proteins by releasing mediators. Fractalkine signaling controls these functions of microglial cells in part by regulating their timely recruitment at sites of developing synapses. Finally, on-going research suggests that this signaling pathway is also a key player in neurodevelopmental disorders.

Astrocyte and microglial control of glutamatergic signalling: a primer on understanding the disruptive role of chronic stress

It is now well established that chronic stress can induce significant structural remodelling of astrocytes and microglia. Until recently, however, the full significance of these morphological disturbances has remained unclear. Clues to the significance of astroglial re-organisation following stress are beginning to emerge from a compelling literature describing how astrocytes contribute to glutamatergic neurotransmission. The present review briefly summarises these two fields of research, identifies points of overlap and, in doing so, pin-points future research directions for stress neurobiology. Ultimately, understanding how chronic stress can disrupt the interactions of astrocytes and microglia with neurones has the potential in the future to improve the development of therapeutics designed to treat stress-related illnesses such as depression.

Cholesterol metabolite cholestane-3β,5α,6β-triol suppresses epileptic seizures by negative modulation of voltage-gated sodium channels

Imbalance of excitation and inhibition in neurons is implicated in the pathogenesis of epilepsy. Voltage-gated sodium channels, which play a vital role in regulating neuronal excitability, are one of the major targets for developing anti-epileptic drugs. Here we provide evidence that cholestane-3β,5α,6β-triol (triol), a major metabolic oxysterol of cholesterol, is an effective state-dependent negative sodium channels modulator. Triol reduced Na(+) current density in a concentration-dependent manner. 10 μM triol shifted steady-state/fast/slow inactivation curves of sodium channels toward the hyperpolarizing direction. Additionally, triol reduced voltage-gated sodium currents in a voltage- and frequency-dependent manner. In a kainic acid-induced seizures mouse model, triol (25 mg/kg) significantly increased the latency of seizure onset and attenuated seizure severity. Our findings provide novel insights for understanding the modulatory role of a small molecular oxysterol on voltage-gated sodium channels and suggest triol may represent a novel and promising candidate for epilepsy intervention.

Microglial Kv1.3 Channels and P2Y12 Receptors Differentially Regulate Cytokine and Chemokine Release from Brain Slices of Young Adult and Aged Mice

Brain tissue damage following stroke or traumatic brain injury is accompanied by neuroinflammatory processes, while microglia play a central role in causing and regulating neuroinflammation via production of proinflammatory substances, including cytokines and chemokines. Here, we used brain slices, an established in situ brain injury model, from young adult and aged mice to investigate cytokine and chemokine production with particular focus on the role of microglia. Twenty four hours after slice preparation, higher concentrations of proinflammatory cytokines, i.e. TNF-α and IL-6, and chemokines, i.e. CCL2 and CXCL1, were released from brain slices of aged mice than from slices of young adult mice. However, maximal microglial stimulation with LPS for 24 h did not reveal age-dependent differences in the amounts of released cytokines and chemokines. Mechanisms underlying microglial cytokine and chemokine production appear to be similar in young adult and aged mice. Inhibition of microglial Kv1.3 channels with margatoxin reduced release of IL-6, but not release of CCL2 and CXCL1. In contrast, blockade of microglial P2Y12 receptors with PSB0739 inhibited release of CCL2 and CXCL1, whereas release of IL-6 remained unaffected. Cytokine and chemokine production was not reduced by inhibitors of Kir2.1 K+ channels or adenosine receptors. In summary, our data suggest that brain tissue damage-induced production of cytokines and chemokines is age-dependent, and differentially regulated by microglial Kv1.3 channels and P2Y12 receptors.

Intracellular calcium dynamics in cortical microglia responding to focal laser injury in the PC::G5-tdT reporter mouse

Microglia, the resident immune cells of the brain parenchyma, are highly responsive to tissue injury. Following cell damage, microglial processes redirect their motility from randomly scouting the extracellular space to specifically reaching toward the compromised tissue. While the cell morphology aspects of this defense mechanism have been characterized, the intracellular events underlying these responses remain largely unknown. Specifically, the role of intracellular Ca²⁺ dynamics has not been systematically investigated in acutely activated microglia due to technical difficulty. Here we used live two-photon imaging of the mouse cortex ubiquitously expressing the genetically encoded Ca²⁺ indicator GCaMP5G and fluorescent marker tdTomato in central nervous system microglia. We found that spontaneous Ca²⁺ transients in microglial somas and processes were generally low (only 4% of all microglia showing transients within 20 min), but baseline activity increased about 8-fold when the animals were treated with LPS 12 h before imaging. When challenged with focal laser injury, an additional surge in Ca²⁺ activity was observed in the somas and protruding processes. Notably, coherent and simultaneous Ca²⁺ rises in multiple microglial cells were occasionally detected in LPS-treated animals. We show that Ca²⁺ transients were pre-dominantly mediated via purinergic receptors. This work demonstrates the usefulness of genetically encoded Ca²⁺ indicators for investigation of microglial physiology.

Modulation of microglial process convergence toward neuronal dendrites by extracellular calcium

Extracellular calcium concentrations in the brain fluctuate during neuronal activities and may affect the behavior of brain cells. Microglia are highly dynamic immune cells of the brain. However, the effects of extracellular calcium concentrations on microglial dynamics have not been investigated. Here, we addressed this question in mouse brain slices and in vivo using two-photon microscopy. We serendipitously found that extracellular calcium reduction induced microglial processes to converge at distinct sites, a phenomenon we termed microglial process convergence (MPCs). Our studies revealed that MPCs target neuronal dendrites independent of neuronal action potential firing and is mediated by ATP release and microglial P2Y12 receptors. These results indicate that microglia monitor and interact with neurons during conditions of cerebral calcium reduction in the normal and diseased brain.

Receptors, ion channels, and signaling mechanisms underlying microglial dynamics

Microglia, the innate immune cells of the CNS, play a pivotal role in brain injury and disease. Microglia are extremely motile; their highly ramified processes constantly survey the brain parenchyma, and they respond promptly to brain damage with targeted process movement toward the injury site. Microglia play a key role in brain development and function by pruning synapses during development, phagocytosing apoptotic newborn neurons, and regulating neuronal activity by direct microglia-neuron or indirect microglia-astrocyte-neuron interactions, which all depend on their process motility. This review highlights recent discoveries about microglial dynamics, focusing on the receptors, ion channels, and signaling pathways involved.

Immune cell dynamics in the CNS: Learning from the zebrafish

A major question in research on immune responses in the brain is how the timing and nature of these responses influence physiology, pathogenesis or recovery from pathogenic processes. Proper understanding of the immune regulation of the human brain requires a detailed description of the function and activities of the immune cells in the brain. Zebrafish larvae allow long-term, noninvasive imaging inside the brain at high-spatiotemporal resolution using fluorescent transgenic reporters labeling specific cell populations. Together with recent additional technical advances this allows an unprecedented versatility and scope of future studies. Modeling of human physiology and pathology in zebrafish has already yielded relevant insights into cellular dynamics and function that can be translated to the human clinical situation. For instance, in vivo studies in the zebrafish have provided new insight into immune cell dynamics in granuloma formation in tuberculosis and the mechanisms involving treatment resistance. In this review, we highlight recent findings and novel tools paving the way for basic neuroimmunology research in the zebrafish. GLIA 2015;63:719-735.