The immune system and the nervous system

Magnetically-targetable outer-membrane vesicles for sonodynamic eradication of antibiotic-tolerant bacteria in bacterial meningitis

Treatment of acute bacterial meningitis is difficult due to the impermeability of the blood-brain barrier, greatly limiting the antibiotic concentrations that can be achieved in the brain. Escherichia coli grown in presence of iron-oxide magnetic nanoparticles secrete large amounts of magnetic outer-membrane vesicles (OMVs) in order to remove excess Fe from their cytoplasm. OMVs are fully biomimetic nanocarriers, but can be inflammatory. Here, non-inflammatory magnetic OMVs were prepared from an E. coli strain in which the synthesis of inflammatory lipid A acyltransferase was inhibited using CRISPR/Cas9 mediated gene knockout. OMVs were loaded with ceftriaxone (CRO) and meso-tetra-(4-carboxyphenyl)porphine (TCPP) and magnetically driven across the blood-brain barrier for sonodynamic treatment of bacterial meningitis. ROS-generation upon ultrasound application of CRO- and TCPP-loaded OMVs yielded similar ROS-generation as by TCPP in solution. In vitro, ROS-generation by CRO- and TCPP-loaded OMVs upon ultrasound application operated synergistically with CRO to kill a hard-to-kill, CRO-tolerant E. coli strain. In a mouse model of CRO-tolerant E. coli meningitis, CRO- and TCPP-loaded OMVs improved survival rates and clinical behavioral scores of infected mice after magnetic targeting and ultrasound application. Recurrence did not occur for at least two weeks after arresting treatment.

Comparing RNA-sequencing datasets from astrocytes, oligodendrocytes, and microglia in multiple sclerosis identifies novel dysregulated genes relevant to inflammation and myelination

Central nervous system (CNS) inflammation is a key factor in multiple sclerosis (MS). Invasion of peripheral immune cells into the CNS resulting from an unknown signal or combination of signals results in activation of resident immune cells and the hallmark feature of the disease: demyelinating lesions. These lesion sites are an amalgam of reactive peripheral and central immune cells, astrocytes, damaged and dying oligodendrocytes, and injured neurons and axons. Sustained inflammation affects cells directly located within the lesion site and further abnormalities are apparent diffusely throughout normal-appearing white matter and grey matter. It is only relatively recently, using animal models, new tissue sampling techniques, and next-generation sequencing, that molecular changes occurring in CNS resident cells have been broadly captured. Advances in cell isolation through Fluorescence Activated Cell Sorting (FACS) and laser-capture microdissection together with the emergence of single-cell sequencing have enabled researchers to investigate changes in gene expression in astrocytes, microglia, and oligodendrocytes derived from animal models of MS as well as from primary patient tissue. The contribution of some dysregulated pathways has been followed up in individual studies; however, corroborating results often go unreported between sequencing studies. To this end, we have consolidated results from numerous RNA-sequencing studies to identify and review novel patterns of differentially regulated genes and pathways occurring within CNS glial cells in MS. This article is categorized under: Neurological Diseases > Molecular and Cellular Physiology.

Controllable and Uncontrollable Stress Differentially Impact Fear Conditioned Alterations in Sleep and Neuroimmune Signaling in Mice

Stress induces neuroinflammation and disrupts sleep, which together can promote a number of stress-related disorders. Fear memories associated with stress can resurface and reproduce symptoms. Our previous studies have demonstrated sleep outcomes can be modified by stressor controllability following stress and fear memory recall. However, it is unknown how stressor controllability alters neuroinflammatory signaling and its association with sleep following fear memory recall. Mice were implanted with telemetry transmitters and experienced escapable or inescapable footshock and then were re-exposed to the shuttlebox context one week later. Gene expression was assessed with Nanostring® panels using RNA extracted from the basolateral amygdala and hippocampus. Freezing and temperature were examined as behavioral measures of fear. Increased sleep after escapable stress was associated with a down-regulation in neuro-inflammatory and neuro-degenerative related genes, while decreased sleep after inescapable stress was associated with an up-regulation in these genes. Behavioral measures of fear were virtually identical. Sleep and neuroimmune responses appear to be integrated during fear conditioning and reproduced by fear memory recall. The established roles of disrupted sleep and neuroinflammation in stress-related disorders indicate that these differences may serve as informative indices of how fear memory can lead to psychopathology.

Action-Shapers and Their Neuro-Immunological Foundations

Not all our intentions translate into actions, as our capacity to act may be influenced by a variety of mental and biochemical factors. In this article, we present a comprehensive account of how neuro-immunological processes affect our intentional abilities and our capacity to act. We do so by extending the theory of thought-shapers (TTS) through the notion of action-shapers and combining this theory with the essential embodiment thesis (EE). This thesis about the mind-body relation says that human minds are necessarily and completely embodied. Action-shapers dynamically constitute the action-space of individuals, affecting their capacity to take action or to select one course of action over another. We highlight the effects and interactions of neuro-immunological effective processes in the body to demonstrate how they shape the action-space. In this article, we consider neuro-immunological effective processes that influence the gut-brain axis, chronic stress, high levels of sugar intake, the amygdala and the effects of prolonged stress. We investigate the effects of these processes on the perception and on the capacity to form intentions and act on them. We conclude the paper by providing a concise account of action-shapers, in which we attempt to summarize the line of argumentation and provide suggestions for further research.

COVID-19, Symptoms with Pre-Existing and Not Pre-Existing Neurological Disorders in Pediatrics

Objective The symptoms of coronavirus disease 2019 (COVID-19) in children with pre-existing neurological disease are unknown. We aimed to find out the difference in the symptoms of children with pre-existing neurological disease and those without.

Methods In this single-center, retrospective, cohort study, 96 pediatric patients who had COVID-19 between March 2020 and April 2021 were enrolled.

Results There were 35 males and 61 females. The median age was 14 years (interquartile range [IQR] 10.25–16). Fever (38.5%), headache (35.4%), and cough (32.3%) were the most common symptoms. In 53.1%, neurological complaints (headache, taste-smell loss, vertigo, febrile seizure, coma, and ataxia), in 40.6%, respiratory symptoms (cough, dyspnea, rhinitis, and pharyngitis), and in 8.3%, gastrointestinal symptoms (gastroenteritis, vomiting, nausea, and abdominal pain) were seen. While 23 (62.2%) patients with fever did not have neurological complaints, 14 (37.8%) had neurological complaints (p = 0.017). Eight (21.6%) patients with fever were hospitalized (p = 0.067). Fever was seen significantly more frequently with pre-existing neurological disease (p < 0.001). Younger children were more likely to have fever (p = 0.008). Headaches and taste–smell loss were seen more frequently in patients with no pre-existing neurological disease (p < 0.001, p = 0.034, respectively). The patients with headaches were older than the ones without headaches (p < 0.001). Patients with headaches and loss of taste and smell were older than those without (p = 0.003).

Conclusion Neurological symptoms differed significantly between those who had pre-existing neurological disease and those who did not. Headaches and taste–smell loss were seen more frequently in patients with no pre-existing neurological disease. Fever was significantly higher in patients who had pre-existing neurological disease.

Cytokines in the Brain and Neuroinflammation: We Didn’t Starve the Fire!

In spite of the brain-protecting tissues of the skull, meninges, and blood-brain barrier, some forms of injury to or infection of the CNS can give rise to cerebral cytokine production and action and result in drastic changes in brain function and behavior. Interestingly, peripheral infection-induced systemic inflammation can also be accompanied by increased cerebral cytokine production. Furthermore, it has been recently proposed that some forms of psychological stress may have similar CNS effects. Different conditions of cerebral cytokine production and action will be reviewed here against the background of neuroinflammation. Within this context, it is important to both deepen our understanding along already taken paths as well as to explore new ways in which neural functioning can be modified by cytokines. This, in turn, should enable us to put forward different modes of cerebral cytokine production and action in relation to distinct forms of neuroinflammation.

Maternal nematode infection upregulates expression of Th2/Treg and diapedesis related genes in the neonatal brain

Intestinal nematode infections common during pregnancy have recently been shown to have impacts that extend to their uninfected offspring including altered brain gene expression. If maternal immune signals reach the neonatal brain, they might alter neuroimmune development. We explored expression of genes associated with four distinct types of T cells (Th1, Th2, Th17, Treg) and with leukocyte transendothelial migration and endocytosis transport across the blood–brain barrier (BBB) in the postnatal brain of offspring of nematode-infected mice, through secondary analysis of a whole brain gene expression database. Th1/Th17 expression was lowered by maternal infection as evidenced by down-regulated expression of IL1β, Th1 receptors and related proteins, and of IL22 and several Th17 genes associated with immunopathology. In contrast, Th2/Treg related pathways were upregulated as shown by higher expression of IL4 and TGF-β family genes. Maternal infection also upregulated expression of pathways and integrin genes involved in transport of leukocytes in between endothelial cells but downregulated endosome vesicle formation related genes that are necessary for endocytosis of immunoglobulins across the BBB. Taken together, pup brain gene expression indicates that maternal nematode infection enhanced movement of leukocytes across the neonatal BBB and promoted a Th2/Treg environment that presumably minimizes the proinflammatory Th1 response in the pup brain.

Human β-Defensin 2 and Its Postulated Role in Modulation of the Immune Response

Studies described so far suggest that human β-defensin 2 is an important protein of innate immune response which provides protection for the human organism against invading pathogens of bacterial, viral, fungal, as well as parasitical origin. Its pivotal role in enhancing immunity was proved in infants. It may also be considered a marker of inflammation. Its therapeutic administration has been suggested for maintenance of the balance of systemic homeostasis based on the appropriate composition of the microbiota. It has been suggested that it may be an important therapeutic tool for modulating the response of the immune system in many inflammatory diseases, offering new treatment modalities. For this reason, its properties and role in the human body discussed in this review should be studied in more detail.

Depressive and Neurocognitive Disorders in the Context of the Inflammatory Background of COVID-19

The dysfunctional effects of the coronavirus disease 2019 (COVID-19) infection on the nervous system are established. The manifestation of neuropsychiatric symptoms during and after infection is influenced by the neuroinvasive and neurotrophic properties of SARS-CoV-2 as well as strong inflammation characterised by a specific "cytokine storm". Research suggests that a strong immune response to a SARS-CoV-2 infection and psychological stressors related to the pandemic may cause chronic inflammatory processes in the body with elevated levels of inflammatory markers contributing to the intensification of neurodegenerative processes. It is suggested that neuroinflammation and associated central nervous system changes may significantly contribute to the etiopathogenesis of depressive disorders. In addition, symptoms after a COVID-19 infection may persist for up to several weeks after an acute infection as a post-COVID-19 syndrome. Moreover, previous knowledge indicates that among SSRI (selective serotonin reuptake inhibitor) group antidepressants, fluoxetine is a promising drug against COVID-19. In conclusion, further research, observation and broadening of the knowledge of the pathomechanism of a SARS-CoV-2 infection and the impact on potential complications are necessary. It is essential to continue research in order to assess the long-term neuropsychiatric effects in COVID-19 patients and to find new therapeutic strategies.

SARS-CoV-2 Infection in the Central and Peripheral Nervous System-Associated Morbidities and Their Potential Mechanism

The recent outbreak of SARS-CoV-2 infections that causes coronavirus-induced disease of 2019 (COVID-19) is the defining and unprecedented global health crisis of our time in both the scale and magnitude. Although the respiratory tract is the primary target of SARS-CoV-2, accumulating evidence suggests that the virus may also invade both the central nervous system (CNS) and the peripheral nervous system (PNS) leading to numerous neurological issues including some serious complications such as seizures, encephalitis, and loss of consciousness. Here, we present a comprehensive review of the currently known role of SARS-CoV-2 and identify all the neurological problems reported among the COVID-19 case reports throughout the world. The virus might gain entry into the CNS either through the trans-synaptic route via the olfactory neurons or through the damaged endothelium in the brain microvasculature using the ACE2 receptor potentiated by neuropilin-1 (NRP-1). The most critical of all symptoms appear to be the spontaneous loss of breathing in some COVID-19 patients. This might be indicative of a dysfunction within the cardiopulmonary regulatory centers in the brainstem. These pioneering studies, thus, lay a strong foundation for more in-depth basic and clinical research required to confirm the role of SARS-CoV-2 infection in neurodegeneration of critical brain regulatory centers.

Inflammatory and immunological changes caused by noise exposure: A systematic review

Today, due to the growth of industries and spread of the use of various instruments and devices that produce high noise levels, it is necessary to pay more attention to the effects of exposure to noise on organs and tissues in the body. The importance of the immune system in fighting external and pathogenic factors has raised the need to consider external factors (such as harmful physical factors) and make efforts to avoid producing them. In this systematic review, 811 potentially relevant studies were found in Google Scholar, PubMed, and Web of Science databases, of which 32 different English-written articles were included in the study. The method of searching and systematically reviewing articles was based on the assessment tool of the multiple systematic reviews (AMSTAR) method. The results of this study suggested that noise could affect the function of the immune system and its components by affecting other systems and organs of the body, including the central nervous system, auditory system, circulatory system, and endocrine gland. Moreover, it can be hypothesized that noise affects immune system by producing the NADPH oxidase (Nox) and reactive oxygen species (ROS).

Acute Bacterial Meningitis: Challenges to Better Antibiotic Therapy

Bacterial meningitis is a medical emergency requiring highly bactericidal antibiotics to achieve cure. Many challenges exist to achieving optimal patient outcome. First, antibiotics must pass the blood brain barrier. Once in the subarachnoid space, achieving bactericidal therapy involves circumventing antibiotic resistance and, more commonly, antibiotic tolerance arising from the slow growth of bacteria in the nutrient poor cerebrospinal fluid. Finally, bactericidal therapy is most often bacteriolytic, and debris from lysis is highly inflammatory. Controlling damage from lytic products may require adjunctive therapy to prevent neuronal death. These challenges are an extreme example of the different requirements for treating infections in different body sites.

Autoimmunity in acute ischemic stroke and the role of blood-brain barrier: the dark side or the light one?

This article presents a synopsis of the current data on the mechanisms of blood-brain barrier (BBB) alteration and autoimmune response in acute ischemic stroke. Most researchers confirm the relationship between the severity of immunobiochemical changes and clinical outcome of acute ischemic stroke. Ischemic stroke is accompanied by aseptic inflammation, which alters the brain tissue and exposes the co-stimulatory molecules of the immune system and the neuronal antigens. To date, BBB is not considered the border between the immune system and central nervous system, and the local immune subsystems are found within and behind the BBB. BBB disruption contributes to the leakage of brain autoantigens and induction of secondary autoimmune response to neuronal antigens and long-term inflammation. Glymphatic system function is altered and jeopardized both in hemorrhagic and ischemic stroke types. The receptors of innate immunity (toll-like receptor-2 and toll-like receptor-4) are also involved in acute ischemia-reperfusion injury. Immune response is related to the key processes of blood clotting and fibrinolysis. At the same time, the stroke-induced immune activation may promote reparation phenomena in the brain. Subsequent research on the reduction of the acute ischemic brain injury through the target regulation of the immune response is promising.

Lack of Major Histocompatibility Complex Class I Upregulation and Restrictive Infection by JC Virus Hamper Detection of Neurons by T Lymphocytes in the Central Nervous System

The human polyomavirus JC (JCV) infects glial cells in immunosuppressed individuals, leading to progressive multifocal leukoencephalopathy. Polyomavirus JC can also infect neurons in patients with JCV granule cell neuronopathy and JCV encephalopathy. CD8-positive T cells play a crucial role in viral containment and outcome in progressive multifocal leukoencephalopathy, but whether CD8-positive T cells can also recognize JCV-infected neurons is unclear. We used immunohistochemistry to determine the prevalence of T cells in neuron-rich areas of archival brain samples from 77 patients with JCV CNS infections and 94 control subjects. Neurons predominantly sustained a restrictive infection with expression of JCV regulatory protein T antigen (T Ag), whereas glial cells were productively infected and expressed both T Ag and the capsid protein VP1. T cells were more prevalent near JCV-infected cells with intact nuclei expressing both T Ag and VP1 compared with those expressing either protein alone. CD8-positive T cells also colocalized more with JCV-infected glial cells than with JCV-infected neurons. Major histocompatibility complex class I expression was upregulated in JCV-infected areas but could only be detected in rare neurons interspersed with infected glial cells. These results suggest that isolated neurons harboring restrictive JCV infection do not upregulate major histocompatibility complex class I and thus may escape recognition by CD8-positive T cells.

The phagocytes of neonate rat primary mixed glial cultures

The phagocytes present in mechanically dissociated neonate rat cerebral hemispheres have been cultured and characterized both qualitatively and quantitatively. They comprise about 10% of the starting cell suspension and persist but do not proliferate in culture. They do not possess neuronal or neuroglial antigens but do express the leukocyte common antigen and readily ingest both latex beads and opsonized erythrocytes. the latter by an Fc receptor-mediated process. Evidence is presented that these cells are a bona fida component of the neonate central nervous system.

The expression patterns of MHC class I molecules in the developmental human visual system

It has been considered that healthy neurons in central nervous system (CNS) do not express major histocompatibility complex (MHC) class I molecules. However, recent studies clearly demonstrated the expression of functional MHC class I in the mammalian embryonic, neonatal and adult brain. Until now, it is still unknown whether MHC I molecules are expressed in the development of human brain. We collected nine human brain tissues from fetuses aged from 21 to 31 gestational weeks (GW), one newborn of postnatal 55 days and one adult. The expression of MHC class I molecules was detected during the development of visual system in human brain by immunohistochemistry and immunofluorescence. MHC class I proteins were located at lateral geniculate nucleus (LGN) and the expression was gradually increased from 21 GW to 31 GW and reached high levels at 30-31 GW when fine-scale refinement phase was mediated by neural electric activity. However, there was no expression of MHC class I molecules in the visual cortical cortex during all the developmental stages examined. We also concluded that MHC class I molecules were mainly expressed in neurons but not in astrocytes at LGN. In the developing visual system, the expression of β2M protein on neurons was not found in our study.

Activity-dependent regulation of MHC class I expression in the developing primary visual cortex of the common marmoset monkey

Background

Several recent studies have highlighted the important role of immunity-related molecules in synaptic plasticity processes in the developing and adult mammalian brains. It has been suggested that neuronal MHCI (major histocompatibility complex class I) genes play a role in the refinement and pruning of synapses in the developing visual system. As a fast evolutionary rate may generate distinct properties of molecules in different mammalian species, we studied the expression of MHCI molecules in a nonhuman primate, the common marmoset monkey (Callithrix jacchus).

Methods and results

Analysis of expression levels of MHCI molecules in the developing visual cortex of the common marmoset monkeys revealed a distinct spatio-temporal pattern. High levels of expression were detected very early in postnatal development, at a stage when synaptogenesis takes place and ocular dominance columns are formed. To determine whether the expression of MHCI molecules is regulated by retinal activity, animals were subjected to monocular enucleation. Levels of MHCI heavy chain subunit transcripts in the visual cortex were found to be elevated in response to monocular enucleation. Furthermore, MHCI heavy chain immunoreactivity revealed a banded pattern in layer IV of the visual cortex in enucleated animals, which was not observed in control animals. This pattern of immunoreactivity indicated that higher expression levels were associated with retinal activity coming from the intact eye.

Conclusions

These data demonstrate that, in the nonhuman primate brain, expression of MHCI molecules is regulated by neuronal activity. Moreover, this study extends previous findings by suggesting a role for neuronal MHCI molecules during synaptogenesis in the visual cortex.

Approaches for immunological tolerance induction to stem cell-derived cell replacement therapies

The shortage of donors for organ transplantation and also to treat degenerative diseases has led to the development of the new field of regenerative medicine. One aim of this field, in addition to in vivo induction of endogenous tissue regeneration, is to utilize stem cells as a supplementary source of cells to repair or replace tissues or organs that have ceased to function owing to ageing or autoimmunity. Embryonic stem cells hold promise in this respect because of their developmental capacity to generate all tissues within the body. More recently, the discovery of induced pluripotent stem cells, somatic cells reprogrammed to a primitive embryonic-like state by the introduction of pluripotency factors, may also act as an important cell source for cell replacement therapy. However, before cell replacement therapy can become a reality, one must consider how to overcome the potential transplant rejection of stem cell-derived products. There are several potential ways to circumvent the hurdles presented by the immune system in this setting, not least the induction of immunological tolerance in the host. In this review, we consider this and other approaches for engendering acceptance of stem cell-derived tissues.

Neuronal MHC class I molecules are involved in excitatory synaptic transmission at the hippocampal mossy fiber synapses of marmoset monkeys

Several recent studies suggested a role for neuronal major histocompatibility complex class I (MHCI) molecules in certain forms of synaptic plasticity in the hippocampus of rodents. Here, we report for the first time on the expression pattern and functional properties of MHCI molecules in the hippocampus of a nonhuman primate, the common marmoset monkey (Callithrix jacchus). We detected a presynaptic, mossy fiber-specific localization of MHCI proteins within the marmoset hippocampus. MHCI molecules were present in the large, VGlut1-positive, mossy fiber terminals, which provide input to CA3 pyramidal neurons. Furthermore, whole-cell recordings of CA3 pyramidal neurons in acute hippocampal slices of the common marmoset demonstrated that application of antibodies which specifically block MHCI proteins caused a significant decrease in the frequency, and a transient increase in the amplitude, of spontaneous excitatory postsynaptic currents (sEPSCs) in CA3 pyramidal neurons. These findings add to previous studies on neuronal MHCI molecules by describing their expression and localization in the primate hippocampus and by implicating them in plasticity-related processes at the mossy fiber-CA3 synapses. In addition, our results suggest significant interspecies differences in the localization of neuronal MHCI molecules in the hippocampus of mice and marmosets, as well as in their potential function in these species.

Immunity and cognition: what do age-related dementia, HIV-dementia and 'chemo-brain' have in common?

Until recently, dogma dictated that the immune system and the central nervous system (CNS) live mostly separate, parallel lives, and any interactions between the two were assumed to be limited to extreme cases of pathological insult. It was only a decade ago that T cells in the injured brain were shown to play a protective rather than a destructive role. In this article, we explore the role of the immune system in the healthy brain, focusing on the key function that T lymphocytes have in the regulation of cognition. We discuss candidate mechanisms underlying T cell-mediated control of cognitive function in human cognitive diseases associated with immune decline, such as age- and HIV-related dementias, 'chemo-brain' and others.

Differential expression of major histocompatibility complex class I molecules in the brain of a New World monkey, the common marmoset (Callithrix jacchus)

It has been supposed that central nervous neurons do not express MHC class I molecules. However, recent studies clearly demonstrated functional MHC class I expression in the rodent brain. In the present study, we have extended these studies and investigated the presence of MHC class I transcripts and proteins in the brain of a non-human primate species, the common marmoset monkey (Callithrix jacchus). Using in-situ hybridization, we found strong expression of MHC class I transcripts in neocortex, hippocampal formation, substantia nigra and nucleus ruber. In-situ hybridization with emulsion autoradiography demonstrated MHC class I mRNA in distinct pyramidal neurons of cortex and hippocampus, in granule neurons of the dentate gyrus, in dopaminergic neurons of substantia nigra and in motor neurons of nucleus ruber. Immunocytochemistry confirmed MHC class I protein expression in these neurons. Two monoclonal antibodies, MRC-Ox18 and HB115, reacted differentially with MHC class I proteins on neuronal and non-neuronal cells, respectively. Interestingly, in marmoset monkeys that were immunosuppressed with FK506 (tacrolimus), expression of neuronal MHC class I proteins, which could be detected with MRC-Ox18, was either very low (neocortex, nucleus ruber, substantia nigra) or absent (hippocampus). In contrast, class I expression in endothelial cells, which was detected by HB115, was not affected by immunosuppression. Our data show that selected neurons in the brain of a non-human primate express MHC class I molecules and that this expression can be modulated by immunosuppression.

Intratumoral injection of IL-2-activated NK cells enhances the antitumor effect of intradermally injected paraformaldehyde-fixed tumor vaccine in a rat intracranial brain tumor model

Combined therapy with a fixed-tumor cell vaccine and intratumoral injection of NK cells induced strong tumor regression of rat glioma. Rat 9L glioma cells were inoculated into syngeneic male rats at the flank (subcutaneous tumor model) or at the basal ganglia of the right hemisphere (intracranial tumor model). Rats were intradermally injected three times with vaccine comprising fixed 9L cells, IL-2- and GMCSF-microparticles, and tuberculin prior to (protective studies) or after (therapeutic studies) challenge with live 9L cells. In the protective studies, the vaccine alone achieved significant tumor growth inhibition and elongation of mean life span in both the subcutaneous and intracranial tumor models. No therapeutic effect was observed in the intracranial tumor model with the vaccine alone. However, intratumoral injection of rat NK cells strongly assisted the therapeutic effect of the vaccine in the brain tumor model and resulted in a statistically significant elongation of life span. We propose that intratumoral injection of NK cells may not only kill brain tumor cells directly, but also trigger a strong immune response in the focal lesion of the brain after vaccination.

Central nervous system virion detection in acute measles: histopathological, ultrastructural and pathogenetic aspects

Histopathological and ultrastructural studies of 23 patients who died with clinical diagnosis of measles were carried out. In 12 cases viral nucleocapsids were searched by electron microscopy and detected in 100% of the cases in the lungs and in 50% of the cases in the central nervous system. They were mostly intranuclear. Histopathological changes associated to neurological alterations and the detection of virion are discussed in relation to acute and delayed clinical manifestations.

T cell subsets in peripheral blood and cerebrospinal fluid from children with aseptic meningitis

T cell subsets in peripheral blood (PB) and cerebrospinal fluid (CSF) obtained from patients with aseptic meningitis were studied using quantitative two-color fluorescence analysis with a flow cytometer. The percentage of HLA-DR+/CD3+ lymphocytes (activated T cells) in CSF was significantly increased in the recovery phase when compared to the acute phase, while no significant change in the activated T cells in PB was observed. More interestingly, CD4+ T lymphocytes in CSF were increased in the acute phase and subsequently decreased in the recovery phase. Instead, CD8+ T lymphocytes gradually accumulated into the CSF in the recovery phase, resulting in a successive decrease in the CD4/CD8 ratio. On the other hand, the CD4/CD8 ratio in PB remained normal during the course of aseptic meningitis. The present results suggest that T lymphocytes (CD4+ subset in the acute phase and CD8+ in the recovery phase) could be infiltrated and further activated at the site of inflammation, possibly in the subarachnoid space in the patients with aseptic meningitis.

Cerebrospinal fluid proteins in neurosyphilis and HIV infection

This paper briefly reviews the factors which influence the concentrations of proteins, particularly immunoglobulins, within the CSF and how antibodies which are locally synthesized within the central nervous system can be detected by the laboratory. The use of nitrocellulose immunoblotting for the identification of antibodies which are specific to Treponema pallidum and Human Immunodeficiency Virus Type-1 are discussed.

Transfection-induced tumor necrosis factor-alpha increases the susceptibility of human glioma cells to lysis by lymphokine-activated killer cells: continuous expression of intercellular adhesion molecule-1 on the glioma cells

To develop more effective adoptive immunotherapy, we transfected the human tumor necrosis factor-alpha (TNF-alpha) gene into human glioma cells (U251-SP), which were used as target cells. TNF-alpha is known to increase both the expression of intercellular adhesion molecule-1 (ICAM-1) on the surface of glioma cells and the susceptibility of glioma cells to lymphokine-activated killer (LAK) cell cytolysis. We compared the expression of ICAM-1 induced by TNF-alpha generated by the TNF-alpha gene-transfected cells with that induced by exogenously added TNF-alpha. When the TNF-alpha gene was transfected into U251-SP cells, the expression of ICAM-1 was detected on the cell surface from 3 days after the transfection and continued until at least 9 days. In contrast, it was expressed only transiently in the case of exogenously added TNF-alpha. Also, the cytolytic activity of LAK cells induced by transfection-induced TNF-alpha was significantly stronger than that induced by exogenously added TNF-alpha. The increased susceptibility was quenched by anti-ICAM-1 monoclonal antibody. These data indicated that continuous expression of ICAM-1 induced by TNF-alpha gene transfection of glioma cells resulted in higher cytolytic activity of LAK cells.

Role of histocompatibility antigen gene and protooncogene expressions in intracerebral tumorigenicity of mouse neuroblastoma

The role of N-myc, c-src, and major histocompatibility complex (MHC, H-2 in the mouse) class I antigen gene expressions in dimethyl sulfoxide (DMSO)-induced differentiation and intracerebral tumorigenicity was examined using a mouse MNB85 neuroblastoma cell line. A fluorescence-activated cell sorter disclosed cell-surface MHC enhancement by DMSO, causing an increase in cytotoxic T-lymphocyte sensitivity. Southern blot analysis verified a single copy of the proto-oncogenes and MHC deoxyribonucleic acids in both untreated and DMSO-treated MNB85 cells. Northern blot analysis indicated that DMSO treatment induced a decrease in N-myc and an increase in c-src and MHC messenger ribonucleic acids. Nuclear run-off transcription assay revealed down-regulation of N-myc at a posttranscriptional level, contrasted with primary up-regulation of c-src at a transcriptional level. Immunoprecipitation after treatment with enzyme endo-beta-N-acetyl-glycoseamidase H proved that the terminal glycosylation of MHC heavy-chain gene products normally occurs in the Golgi apparatus of MNB85 cells. Intracerebral tumorigenicity assay showed that cells highly MHC-expressed by DMSO were less tumorigenic than untreated cells in association with DMSO-augmented cytotoxic T-lymphocyte susceptibility. These results suggest that proto-oncogenes may be linked to cellular differentiation, while cell-surface MHC gene expression influences intracerebral immunosurveillance.

A morphological and ultrastructural investigation of normal mouse brain tissue after intracerebral injection of tumor necrosis factor

Morphological and ultrastructural changes in normal mouse brain tissue were investigated after intracerebral stereotactic injections of tumor necrosis factor (specific activity: 2.0 x 10(6) U/mg protein) into the right frontal lobe. The mice received either a single infusion or multiple tumor necrosis factor infusions in three different dose groups (10, 100, or 500 U). Compared with sham-treated control mice that received adjusted intracerebral injections of purified albumin, the tumor necrosis factor-treated mice in all dose groups did not show any specific in vivo behavioral abnormalities during the 2 months of study following the infusions. Histological studies revealed hemorrhage attributable to the mechanics of the intracerebral infusions, a thickening of the arachnoid membranes, a reactive gliosis, and neutrophilic and/or mononuclear cell infiltration along the infusion pathway. A local neutrophilic response was prominent 1 day after tumor necrosis factor injection. An immunohistochemical analysis indicated that the mononuclear cell infiltration consisted of lymphocytes and macrophages. Except for the transient neutrophilic infiltration, these histological alterations did not differ from those seen in the sham-treated control groups, and most nonspecific reactive changes disappeared within 8 weeks after the injections. Furthermore, an ultrastructural study showed no apparent pathological changes in the cytoplasmic organelles of neuronal, glial, and endothelial cells in the tumor necrosis factor-injected mouse specimens. These results suggest that the tumor necrosis factor injections caused no specific toxicity and did not alter the parenchymal and stromal cells comprising normal mouse brain tissue.

Immunology of central nervous system tumors

With progress in cellular immunology and the development of hybridoma technology, the idea of manipulating host-tumor immune interactions to improve the prognosis of brain tumors has aroused renewed interest. Although no brain tumor-specific antigens have been found, and in spite of the wide antigenic heterogeneity of brain tumor cells, some monoclonal antibodies possessing restricted specificity have been isolated and their potential clinical applications investigated. One of the most pronounced changes in the cellular immune responses of brain tumor patients is a profound depression of the T4-helper lymphocytes. Clinical and laboratory trials are under way to assess the ability of lymphokines, such as gamma-interferon or interleukin-2, to restore immunologic competence in these patients and potentiate a specific anti-tumor immunologic response. Recent work suggests that the endothelium-astrocyte complex may have a pivotal role in assisting the escape of brain tumors from the host's immunologic responses, since it is responsible for the intracerebral sequestration of antigens and local anti-tumor responses. In this review, the data on the antigenic properties of central nervous system tumors and the host's humoral and cellular immune responses to them are analyzed and potential immunologic therapies are discussed.

Enhanced H-2 expression and T-cell-dependent rejection after intracerebral transplantation of the murine lymphoma YAC-1

The relationship between MHC class I (H-2) expression and tumorigenicity was investigated after intracerebral inoculation of the murine lymphoma YAC-1 and its H-2 negative variant, A.H-2-. YAC-1 was less tumorigenic than A.H-2- in normal as well as NK-depleted syngeneic A/Sn mice. However, in T-cell-depleted syngeneic mice YAC-1 was as tumorigenic as A.H-2-. Following intracerebral growth, the H-2 expression of YAC-1 was markedly enhanced in a similar fashion as after intraperitoneal passage. The A.H-2- variant remained H-2 negative after intracranial passage. The H-2 negative variant cells were not rejected from the brain even when intermixed with wild-type YAC-1 cells prior to intracerebral inoculation, excluding an "innocent bystander" effect. In vitro, the intracerebrally passaged YAC-1 line showed enhanced sensitivity to lysis by H-2 Kk Dd (H-2a) specific CTLs but decreased sensitivity to NK cells. The A.H-2- line was unchanged. Our data suggest that the lack of H-2 molecules may facilitate the growth of antigenic tumor cells in the brain due to escape from T-cell-mediated immunosurveillance. Our data also suggest, in line with other recent findings, that intracerebrally growing tumor cells are sheltered from NK cell-mediated rejection.

Immune response in deep cervical lymph nodes and spleen in the mouse after antigen deposition in different intracerebral sites

Brain interstitial and cerebrospinal fluid drainage into the lymphatics was studied by injections of 5 microliters of packed sheep red blood cells (SRBC) injected into the caudate nucleus, the occipital lobe, and the lateral ventricle of the brain in mice. The number of plaque-forming cells (PFC) was determined in the deep cervical lymph nodes, the axillary lymph nodes, and the spleen, and the number of PFC was compared with the response in the same tissues after intravenous immunization with 0.1 ml 10% SRBC. The weight of the deep cervical lymph nodes increased 3.0 times on day 3 after injection in the brain parenchyma compared with the weight of these nodes after intravenous immunization. The antigen-specific response peaked on day 5, 392 +/- 37 PFC/10(6) for IgG in the deep cervical lymph nodes after antigen deposition in the caudate nucleus, whereas only a minor peak in the antigen-specific response was obtained after intraventricular antigen deposition, 127 +/- 79 PFC x 10(6) for IgG on day 6. There were no increased PFC in any of the lymph nodes after intravenous immunization. The experiments show an antigen-specific response in the deep cervical lymph nodes after intracerebral antigen deposition, whereas antigens deposited in the lateral ventricles drain preferentially to the blood, with a high response in the spleen.

Selective acceptance of MHC class I-deficient tumor grafts in the brain

H-2-deficient (H-2-) tumor variants were accepted equally well compared with H-2+ wild-type cells in the brain of syngeneic mice, while the H-2- cells were selectively eliminated when inoculated extracranially. This indicates a specific absence or suppression of the defense against MHC class I-deficient cells in the brain, suggested to be mediated by NK cells. In contrast, T cell-mediated immune reactions could clearly be detected in the brain under the same experimental conditions. This was shown in control experiments where H-2+ tumor cells were rejected from the brain of preimmunized or allogeneic mice. The present findings may be important for the understanding of neurotropic virus infections, immunology and immunotherapy of brain tumors, as well as for the growing interest in tissue grafting within the central nervous system.

Cerebrospinal fluid and peripheral blood leukocyte subsets in acute inflammation of the CNS

Leukocyte subsets in CSF and peripheral blood (PB) were determined in 21 patients with acute inflammation of the CNS using the monoclonal antibodies OKT3, OKT4, OKT8, Leu12, and OKM1 in an immunoperoxidase slide assay. There was a predominance of OKT3-positive cells in nearly all samples. Significant differences between acute aseptic and bacterial meningitis only were found in CSF and represented by a higher Leu12 and a lower OKT3 percentage in aseptic inflammation and a higher absolute amount of OKT4-, OKM1- and Leu12-positive cells in bacterial meningitis. Comparison between CSF and PB showed significant differences only in aseptic meningitis with a higher percentage of Leu12-positive cells and a lower percentage of OKT8-positive cells in CSF. The OKT4/OKT8 ratio seems to be generally lower in aseptic meningitis but significant differences only were found in comparison with healthy blood donors. In a case of herpes simplex encephalitis the ratio was strongly increased in CSF during the early phase of specific antibody production because of an absolute rise of OKT4-positive cells.

Immunocomplexes in rat and rabbit spinal cord after injury

The possibility that, following a major lesion of the central nervous system, a humoral immune response could be evoked with formation of immune complexes "in situ" was investigated. For this purpose, an immunohistochemical study on rabbit and rat spinal cord at different times after surgical transection was carried out. The peroxidase-antiperoxidase method showed IgG decoration of the myelin sheaths starting a short time after surgery. The sera of intact and injured animals were then tested both by immunohistochemical methods on intact spinal cord sections and by immunoelectrophoresis on a protein extract of homologous spinal cord. The results showed in the rabbit the absence of antibodies to neural antigens before surgical injury and its appearance within a few days after surgery. On the other hand, in the rat, even before the injury, we found antibodies to neural tissue which decreased in the first few hours after injury, and returned to control values during successive days. The same experiments were conducted after a peripheral nerve lesion (sciatic nerve crush), but no immune response could be detected. The possible role of this immune response in the failure of axonal regeneration in mammalian spinal cord is briefly discussed.

Blood-brain barrier in Alzheimer dementia and in non-demented elderly. An immunocytochemical study

Peroxidase-antiperoxidase staining of formalin-fixed brain was employed to compare the blood-brain barrier (BBB) function in five patients with Alzheimer's disease/senile dementia of the Alzheimer type (AD/SDAT) and three patients with AD/SDAT combined with multi-infarct dementia (MID/SDAT) with that of six non-demented aged controls. The diffusion of serum proteins through the BBB was visualized with antisera to albumin, prealbumin, immunoglobulin, C1q, C3c and to fibrinogen. A similar patterns of diffusion was seen in AD/SDAT and non-demented aged individuals. Neuron and glial cells were stained with different antisera in the vicinity of the diffusion. Senile (neuritic) plaques were occasionally visualized with antisera to IgG, C1q and C3c but not with antisera to albumin, prealbumin and fibrinogen in both demented and non-demented aged individuals. Neurofibrillary tangles were not labelled with any of the antisera studied. These results indicate that the BBB is compromised equally in AD/SDAT and in the non-demented elderly.

Role of the blood-brain barrier in the establishment of the immune response against polyoma virus-induced cerebral tumours in hamsters

The existence of an immunological blood-brain barrier (BBB) is well established but its role in cerebral tumour immunology is less well defined. Attempting to clarify this problem we tested the graft rejection of polyoma virus-induced central nervous (CNS) tumours in hamsters after systemic or intracerebral immunization with polyoma virus. Animals were immunized by intracerebral or subcutaneous inoculations of polyoma virus before tumours were induced by intracerebral or intramuscular graft of polyoma-transformed hamster neuroglial cells. The growth of cerebral and muscular tumours was significantly inhibited in animals immunized subcutaneously. In animals immunized intracerebrally the inhibition of growth was highly significant for cerebral tumours and only very slight for intramuscular tumours. These results suggest that the blood-brain barrier allowed immunocompetent effector cells to penetrate inside the CNS but prevented the locally elicited cell-mediated immune response from diffusing outside the CNS. The ability of the brain to develop a local immune response and the partial lack of circulation of immunocompetent cells to cross the BBB could be mainly responsible for the special immune status of the CNS and may greatly interfere with the establishment of an efficient immune response toward brain tumours.

Vestibular neuronitis--serum and CSF virus antibody titer

The cerebrospinal fluid (CSF) findings of patients with vestibular neuronitis were virologically evaluated and discussed in contrast to those of herpes zoster. CSF samples obtained from seven patients with vestibular neuronitis, aged 28 to 55 years, were examined. The results were as follows: The CSF protein level in the vestibular neuronitis showed the peculiar change; i.e. its level was normal at the onset period of vertigo, but it rose to abnormal levels mostly in the period of two weeks, while the cell count remained normal throughout all phases of our study. Herpes simplex virus (HSV) type 1 IgG antibody titers measured by indirect immunofluorescent antibody technique (IF) in paired sera rose in one of the seven cases of vestibular neuronitis, but the antibody titers of the same virus in the CSF were not detected. HSV type 1 IgG antibody titers measured by IF in the CSF were detected in two of seven cases of vestibular neuronitis, but not significant. The ratio of EB virus (EBV) capsid antigen IgG antibody titers in CSF to that in serum ranged from 1:160 to 1:80 in vestibular neuronitis. There was no direct available evidence that vestibular neuronitis caused a break in blood-CSF barrier, an increase in IgG synthesis in the central nervous system or active infection with HSV, varicella zoster virus (VZV), or EBV. In this paper, we summarized the recent information on studies of the CSF and a latent herpes virus infection in order to give perspective to the pathogenesis of vestibular neuronitis.

Psychic distress and the immune response

This minireview surveys recent progress in the field of immunoregulation by the central nervous system. Representative findings from human and animal studies show evidence for significant immunosuppression in states of psychic distress. Mechanisms of immunomodulation are discussed in light of data implicating neuroendocrine, genetic, neuroanatomical, and learning factors. Evidence for reciprocal modulation of immune and nervous systems is considered. A simple hierarchical model proposes traits that are acted on by environment and experience to produce chronic states of mental health vs. psychic distress; these states determine baseline immunocompetence and response to afferent signals during acute immune challenge. Multidisciplinary interest in psychoneuroimmunology has accelerated the rate of inquiry into the mechanistic details of immunoregulation and has generated new appreciation for the pervasive effects of mental status on physiologic homeostasis.

Local and systemic immune response in multiple sclerosis: analysis of CSF inflammatory changes and peripheral blood T-cell subsets

In order to investigate the significance of the immune response in multiple sclerosis (MS), we have compared changes in peripheral blood T-cell subsets to the cellular and humoral responses in the cerebrospinal fluid. Using monoclonal antibodies defining the Leu-3a and Leu-2a phenotypes, we found a highly significant (2P less than 0.001) increase of the Leu-3a/Leu-2a cell ratio in peripheral blood T-cells of multiple sclerosis patients with disease activity (acute phase or progressive form), while patients with inactive disease did not differ from controls. No characteristic alterations in the CSF inflammatory response could be correlated with changes in T-cell subsets in the peripheral blood. There was no significant difference in the cerebrospinal fluid cell count or the mean IgG index between patients with high or low Leu-3a/Leu-2a cell ratios. We conclude that increased CSF IgG synthesis in MS is probably not a direct consequence of the apparent reduction of Leu-2a positive cells in the peripheral blood. Thus the biological significance of the change in immunoregulatory cells in the blood of multiple sclerosis patients remains unknown.