Neuro-immune interactions in the postnatal ventricular-subventricular zone

As described in this book, the interaction between the immune system and the brain can affect multiple cerebral functions, such as: neural remodeling, synaptic plasticity or neurotransmitter releasing. Neurogenic niches are not the exception, in fact, pro-inflammatory cytokines and chemokines exert a strong regulation in neural stem cells (NSCs) of the ventricular-subventricular zone (V-SVZ) by interacting with cell membrane receptors and activating multiple downstream pathways. These neuro-immune interactions modulate quiescence, cell adhesion, migration, self-renewal, differentiation, cytoskeletal rearrangement, and cell survival. In this chapter, we describe the cellular composition and cytoarchitecture of the main neurogenic niche in the adult mammalian brain: the V-SVZ. We also discuss the current evidence indicating that many immunological molecules can control the function of this neurogenic niche in the adult brain under both physiological and pathological conditions.

Japanese encephalitis virus induce immuno-competency in neural stem/progenitor cells

Background

The low immunogenicity of neural stem/progenitor cells (NSPCs) coupled with negligible expression of MHC antigens has popularized their use in transplantation medicine. However, in an inflammatory environment, the NSPCs express costimulatory molecules and MHC antigens, and also exhibit certain immunomodulatory functions. Since NSPCs are the cellular targets in a number of virus infections both during postnatal and adult stages, we wanted to investigate the immunological properties of these stem cells in response to viral pathogen.

Methodology/Principal Findings

We utilized both in vivo mouse model and in vitro neurosphere model of Japanese encephalitis virus (JEV) infection for the study. The NSPCs residing in the subventricular zone of the infected brains showed prominent expression of MHC-I and costimulatory molecules CD40, CD80, and CD86. Using Flow cytometry and fluorescence microscopy, we observed increased surface expression of co-stimulatory molecule and MHC class I antigen in NSPCs upon progressive JEV infection in vitro. Moreover, significant production of pro-inflammatory cyto/chemokines was detected in JEV infected NSPCs by Cytokine Bead Array analysis. Interestingly, NSPCs were capable of providing functional costimulation to allogenic T cells and JEV infection resulted in increased proliferation of allogenic T cells, as detected by Mixed Lymphocyte reaction and CFSE experiments. We also report IL-2 production by NSPCs upon JEV infection, which possibly provides mitogenic signals to T cells and trigger their proliferation.

Conclusion/Significance

The in vivo and in vitro findings clearly indicate the development of immunogenicity in NSPCs following progressive JEV infection, in our case, JEV infection. Following a neurotropic virus infection, NSPCs possibly behave as immunogenic cells and contribute to both the innate and adaptive immune axes. The newly discovered immunological properties of NSPCs may have implications in assigning a new role of these cells as non-professional antigen presenting cells in the central nervous system.

Brain-immune communication pathways

Communication between the central nervous and immune systems lies at the heart of the neuroimmune axis. We trace here some of the major conceptual hurdles which were raised, first against the acceptance of a neuroimmune axis and later in understanding it. We review the major concepts formulated and established during the last two decades and focus on four pathways that have been proposed as important in communication: the neural route, circumventricular organs, blood-brain barrier transport of cytokines, and secretions from BBB cells. These and other pathways have established the existence of a neuroimmune axis, but raise new questions on how they act and interact with one another.

Exaggerated sickness behavior and brain proinflammatory cytokine expression in aged mice in response to intracerebroventricular lipopolysaccharide

Age-associated changes in glial reactivity may predispose individuals to exacerbated neuroinflammatory cytokine responses that are permissive to cognitive and behavioral complications. The purpose of this study was to determine if aging is associated with an exaggerated sickness response to central innate immune activation. Our results show that intracerebroventricular (i.c.v.) administration of lipopolysaccharide (LPS) caused a heightened proinflammatory cytokine response (IL-1beta, IL-6, and TNFalpha) in the cerebellum 2h post i.c.v. injection in aged mice compared to adults. This amplified inflammatory profile was consistent with a brain region-dependent increase in reactive glial markers (MHC class II, TLR2 and TLR4). Moreover, LPS caused a prolonged sickness behavior response in aged mice that was paralleled by a protracted expression of brain cytokines in the cerebellum and hippocampus. Finally, central LPS injection caused amplified and prolonged IL-6 levels at the periphery of aged mice. Collectively, these data establish that activation of the central innate immune system leads to exacerbated neuroinflammation and prolonged sickness behavior in aged as compared to adult mice.

Severe Necrotizing Encephalitis in a Yorkshire Terrier: Topographic and Immunohistochemical Study

Necrotizing encephalitis of the Yorkshire terrier is a chronic non-suppurative encephalitis that was reported in approximately 15 cases worldwide. We report the case of a 10-year-old female Yorkshire terrier with gross evidence of severe cortical degeneration and necrosis. Microscopically, affected areas were mainly located in the cortical white matter and in the mesencephalon without implication of the cerebellum. Cavitation necrosis, demyelination, gemistocytic astrocytosis, marked perivascular lymphocytic cuffing with a diffuse lymphocytic/histiocytic/gitter cell infiltration characterized the lesions. Immunohistochemical analysis identified the major infiltration of T lymphocytes and macrophages with implication of some cytotoxic lymphocytes and IgG-producing plasma cells; depositions of IgG in the affected white matter were also observed. Specific stains did not reveal fungal, protozoal or bacterial organisms and reverse transcriptase-polymerase chain reaction analysis for distemper virus was also negative. The lympho-histiocytic inflammation suggests a T-cell-mediated and a delayed-type immune reaction as a possible pathogenic mechanism for this brain disorder.

Immunohistochemical changes related to ageing in the mouse hippocampus and subventricular zone

We investigated mainly immunohistochemical changes of nestin (a marker of neuroepithelial stem cells) and Ki-67 (a marker of proliferating cells) proteins related to ageing in the mouse hippocampus and subventricular zone (SVZ) using young adult (8 weeks old) and middle-aged (40 weeks old) mice. In the present study, no significant changes in neurons and astrocytes of the hippocampal CA1 sector were found in a middle-aged male ICR mice without severe senile weakness, as compared with young adult animals. In contrast, a significant change in the number of microglia was found in the hippocampal CA1 sector of the middle-aged mice. Furthermore, no significant changes in the number of nestin- and Ki-67-positive cells were observed in the hippocampal CA1 sector of the middle-aged mice. On the other hand, decreases in the number of nestin- and Ki-67-immunopositive cells were observed in the SVZ of the middle-aged mice. Furthermore, a migration of nestin- and Ki-67-immunoreactive cells in the corpus callosum was not observed in the SVZ of the middle-aged mice. In the dentate gyrus, significant decreases in the number of Ki-67-immunopositive cells were observed in the middle-aged mice. Our study also showed that nestin immunoreactivity was observed in both Ki-67-postive cells and astrocytes in the SVZ of young adult mice. These findings emphasize the need to recognize ageing as important factors in studies of microglia, which may help to clarify the role of glial cell structure and function during ageing processes. Furthermore, the present findings suggest that ageing processes may decrease neurogenesis in the corpus callosum, SVZ and dentate gyrus. Thus our present findings provide valuable information for the neurogenesis during ageing processes.

Molecular Aspects of Fever and Hyperthermia

A rise in core temperature during fever usually results from change in the thermocontroller characteristics, resulting in an elevation of the set point of body temperature. Time course and extent of natural fevers are variable, but an upper limit (41 degrees C in humans), at which core temperature is maintained for some time and reduced when the set point of body temperature returns to its normal level, rarely is exceeded. Although any rise in body temperature may result from fever, those rises that are not accompanied by supportive changes in thermoeffector activities are termed hyperthermia.

Subarachnoidal and intraventricular human neurocysticercosis: application of an antigen detection assay for the diagnosis and follow-up

BACKGROUND

Neurocysticercosis (NC) is a parasitic disease of the central nervous system caused by the larval stage of Taenia solium. Although imaging studies are recommended for diagnosis and follow-up of patients, their high cost and restricted availability limit their use. Among various immunological tests, the detection of HP10 antigen in cerebral spinal fluid (CSF) has proved to be a useful tool for the diagnosis of NC in the case of viable but not dead parasites.

OBJECTIVES

This study was designed to evaluate the usefulness of the detection of HP10 antigen for the diagnosis and follow-up of NC patients.

METHODS

The effectiveness of this HP10 assay was analysed for the CSF of 46 confirmed NC cases (21 men, 25 women) who had been clinically and radiologically described.

RESULTS

In 21 of 24 NC patients (87.5%) with viable parasites localized in the SA space at the base of the brain or in the ventricles these were detected by means of the HP10 assay, whilst none of the three patients with viable parasites in the parenchyma or sulci had these detected. Used for the follow-up of patients after cysticidal treatment, it was showed that levels of HP10 dropped significantly only among those patients whose cysticerci were clearly damaged.

CONCLUSIONS

HP10 antigen assay is recommended as a support for diagnosis and follow-up in NC patients with viable parasites localized in the SA space at the base of the brain or in the ventricles, thereby potentially reducing the number of imaging studies required.

Comparison of ventricular and lumbar cerebrospinal fluid T cells in non-inflammatory neurological disorder (NIND) patients

The aim of the present study was to define the cellular composition of ventricular, as compared with lumbar, cerebrospinal fluid (CSF) in patients with non-inflammatory neurological disorders (NIND). We addressed this issue by determining the cellular composition of lumbar CSF from patients with normal pressure hydrocephalus (NPH) who were undergoing lumbar CSF drainage during evaluation for shunting procedures, and evaluating ventricular CSF from a subset of these who underwent subsequent placement of ventriculoperitoneal shunts. We determined the cellular composition of lumbar CSF from 18 patients with NPH, and found that the leukocyte differentials, and relative proportions of CD4+ and CD8+ central memory (TCM), effector memory (TEM) and naive cell (TNaive) populations, were equivalent to those found previously in studies of CSF from patients with NIND. We further evaluated cells in the ventricular CSF of five patients who had previously undergone lumbar drainage. Leukocyte differential counts, as well as CD4+ and CD8+ TCM, TEM, and TNaive proportions, were equivalent in matched ventricular and lumbar CSF samples. These observations support the hypothesis that leukocytes enter the CSF in a selective fashion, at its site of formation in the choroid plexus. The results implicate CSF T cells in the immune surveillance of the central nervous system.

Modulation of Alzheimer's pathology by cerebro-ventricular grafting of hybridoma cells expressing antibodies against Aβ in vivo

Accumulation in brain of the beta-amyloid peptide (Abeta) is considered as crucial pathogenic event causing Alzheimer's disease (AD). Anti-Abeta immune therapy is a powerful means for Abeta clearance from the brain. We recently showed that intravenous injections of anti-Abeta antibodies led to reduction, elevation or no change in brain Abeta42 concentrations of an AD mouse model. We report here, in a second passive immunization protocol, a different bioactivity of same antibodies to alter brain Abeta42 concentrations. Comparing the bioactivity of anti-Abeta antibodies in these two passive immunization paradigms underscores the potential of immune therapy for AD treatment and suggests that both the epitope recognized by the antibody and the mode of antibody administration are crucial for its biological activity.

Nuclear STAT3 translocation in guinea pig and rat brain endothelium during systemic challenge with lipopolysaccharide and interleukin-6

During systemic inflammation, cytokines are released by immune-competent cells into the circulation, which in turn signal the brain to mediate brain-controlled signs of illness. Cytokine-responsive brain cells can be mapped by histological analysis of cytokine-induced transcription factors or transcription factor-associated molecules revealing different cell phenotypes that respond to activation of the immune system. Critical sites mediating cytokine-dependent immuneffector functions can be divided into two groups, one group of responding cells situated along a tight blood-brain barrier (BBB), and a second cell group in structures with an open BBB, e.g., the sensory circumventricular organs (CVOs). Previous reports from our group suggest that activation of the signal transducer and activator of transcription factor 3 (STAT3) during lipopolysaccharide (LPS)-induced systemic inflammation is mediated by interleukin-6 (IL-6) and occurs in astrocytes of the rat CVOs. Here we show in the guinea pig a time-dependent marked LPS-induced STAT3 activation within astrocytes and endothelial cells of the CVOs, within astrocytes located in brain structures with a functional BBB and within the brain endothelium of the entire brain. In addition, systemic treatment of rats with either rat recombinant IL-6 or LPS induced STAT3 activation in brain endothelial cells in a similar way as observed in the guinea pig brain, stressing the involvement of IL-6 in this phenomenon in a more generalized way. The STAT3-activated brain cells are located in critical target structures mediating cytokine action during LPS-induced inflammation. STAT3-controlled transcriptional activation with yet unknown cell-specific functional consequences seems to be involved in this process.

Increased ICAM-1 and VCAM-1 expression in the brains of autoimmune mice

Pathogenic mechanisms of central nervous system (CNS) involvement in systemic lupus erythematosus (SLE) remain unknown. We recently reported the presence of autoantibodies in the brain tissue ex vivo of autoimmune MRL/lpr mice. We postulated that at least some of these autoantibodies are produced in situ because of B-cell entry into the brain. The blood-brain barrier (BBB) blocks the entry of most large molecules and cells into the brain. In certain CNS pathologies, however, immune cells gain entry due to elevated expression of adhesion molecules. This study looked at adhesion molecule expression, ICAM-1 and VCAM-1, in the brains of MRL/lpr mice. Using immunofluorescent antibody binding assays and confocal laser imaging, we show that expression of ICAM-1 and VCAM-1 is elevated in MRL/lpr mice brains at 4 months of age as compared to age-matched controls. These results suggest a possible mechanism for leukocyte entry into the brains of autoimmune mice that in turn suggest immune-mediated pathology in CNS-lupus.

Intrathecal delivery of IFN-gamma protects C57BL/6 mice from chronic-progressive experimental autoimmune encephalomyelitis by increasing apoptosis of central nervous system-infiltrating lymphocytes

The exclusive detrimental role of proinflammatory cytokines in demyelinating diseases of the CNS, such as multiple sclerosis, is controversial. Here we show that the intrathecal delivery of an HSV-1-derived vector engineered with the mouse IFN-gamma gene leads to persistent (up to 4 wk) CNS production of IFN-gamma and inhibits the course of a chronic-progressive form of experimental autoimmune encephalomyelitis (EAE) induced in C57BL/6 mice by myelin oligodendrocyte glycoprotein (MOG)(35-55). Mice treated with the IFN-gamma-containing vector before EAE onset showed an earlier onset but a milder course of the disease compared with control mice treated with the empty vector. In addition, 83% of IFN-gamma-treated mice completely recovered within 25 days post immunization, whereas control mice did not recover up to 60 days post immunization. Mice treated with the IFN-gamma-containing vector within 1 wk after EAE onset partially recovered from the disease within 25 days after vector injection, whereas control mice worsened. Recovery from EAE in mice treated with IFN-gamma was associated with a significant increase of CNS-infiltrating lymphocytes undergoing apoptosis. During the recovery phase, the mRNA level of TNFR1 was also significantly increased in CNS-infiltrating cells from IFN-gamma-treated mice compared with controls. Our results further challenge the exclusive detrimental role of IFN-gamma in the CNS during EAE/multiple sclerosis, and indicate that CNS-confined inflammation may induce protective immunological countermechanisms leading to a faster clearance of encephalitogenic T cells by apoptosis, thus restoring the immune privilege of the CNS.

Intra vitam lumbar and post mortem ventricular cerebrospinal fluid immunoreactive interleukin-6 in Alzheimer's disease patients

OBJECTIVES

In view of contradictory findings in previous studies, to examine the diagnostic value of interleukin-6 measurements in cerebrospinal fluid (CSF) of Alzheimer's disease patients.

MATERIAL AND METHODS

Interleukin-6-immunoreactivity (IL-6-IR) was measured in 169 intra vitam lumbar and 21 post mortem ventricular CSF samples of patients with probable and neuropathologically confirmed Alzheimer's disease (AD), non-AD dementias (NAD), neurological disorders without cognitive impairment (OND) and controls (CON) using a specific sandwich enzyme immunoassay.

RESULTS

Intra vitam lumbar samples had significantly elevated (P < 0.03) IL-6-IR not only in the AD, but also in the NAD and OND group compared with controls. AD patients with late onset (> 65 years) had slightly (P > 0.05) higher values than patients with early onset (< 65 years). In post mortem ventricular fluid, differences among groups did not reach significance (P > 0.05).

CONCLUSION

We conclude that elevations of CSF IL-6-IR can not serve as a diagnostic marker of the disease, but, hypothetically, could reflect presence or activity of IL-6 mediated immunological phenomena in single AD patients.

Distribution and temporal regulation of the immune response in the rat brain to intracerebroventricular injection of interferon-gamma

The response to intracerebroventricular administration of interferon (IFN)-gamma was examined in the adult Wistar rat brain: major histocompatibility complex (MHC) antigens class I and II, CD8 and CD4 antigens, and the macrophage/microglia antigen OX42 were analyzed in respect to saline-injected cases over 1 week. The glial cell type expressing MHC antigens was characterized with double labeling. IFN-gamma was thus found to induce MHC class I and II expression in microglia, identified by tomato lectin histochemistry, and not in GFAP-immunostained astrocytes. MHC antigen-expressing microglia was detected in the periventricular parenchyma, several fields of the cerebral cortex, cerebellum, major fiber tracts, and brainstem superficial parenchyma. Different gradients of density and staining intensity of the MHC-immunopositive elements were observed in these regions, in which MHC class I antigens persisted up to 1 week, when MHC class II induction had declined. Quantitative analysis pointed out the proliferation of OX42-immunoreactive cells in periventricular and basal brain regions. CD8+ T cells were observed in periventricular regions, basal forebrain, and fiber tracts 3 days after IFN-gamma injection and their density markedly increased by 7 days. CD4+ T cells were also seen and they were fewer than CD8+ ones. However, numerous CD4+ microglial cells were observed in periventricular and subpial regions, especially 1 week after IFN-gamma injection. Our data indicate that this proinflammatory cytokine mediates in vivo microglia activation and T cell infiltration in the brain and that the cells involved in this immune response display a regional selectivity and a different temporal regulation of antigen expression.

Cerebral spinal fluid lymphocytes are part of the normal recirculating lymphocyte pool

We have investigated the migration of lymphocytes from blood into the central nervous system (CNS) under normal physiological conditions. Using sheep as our model, we simultaneously sampled blood, lymph and cerebral spinal fluid (CSF). Normal, nonactivated, recirculating lymphocytes can migrate into the CSF in similar concentrations as found in subcutaneous lymph and there is no difference in the temporal appearance between them. Lymphocytes infused into the CNS could be found in cervical lymph nodes. These data suggest that lymphocytes found in the CNS are part of the recirculating lymphocyte pool and do not require activation to enter the CSF.

Intraventricular injection of human immunodeficiency virus type 1 (HIV-1) tat protein causes inflammation, gliosis, apoptosis, and ventricular enlargement

To determine the role of the Tat protein of the human immunodeficiency virus type 1 (HIV-1) in the pathogenesis of HIV-1 associated dementia, recombinant Tat was injected intraventricularly as a single or repeated dose into male Sprague-Dawley rats. Histopathological evaluation showed an initial infiltration of neutrophils one day after Tat injection, followed by macrophages and lymphocytes by 7 days. Tat-injected brains also exhibited astrocytosis, apoptotic cells, and ventricular enlargement 7 days following the last injection. Nuclear magnetic resonance spectroscopic analysis of tissue extracts of hippocampi from Tat-injected rats showed a decrease in the glutamate/g aminobutyric acid ratio. We conclude that the transient extracellular exposure of the central nervous system to Tat protein of HIV can cause a cascade of events leading to the influx of inflammatory cells, glial cell activation, and neurotoxicity.

An immunohistochemical study of the intraventricular macrophages in induced hydrocephalus in prenatal rats following a maternal injection of 6-aminonicotinamide

Hydrocephalus was induced experimentally in prenatal rats following an injection of 6-aminonicotinamide (6-AN) into pregnant rats. The most remarkable change of the dilated lateral ventricles was in a marked increase in the number of intraventricular macrophages, some of which were laden with ingested erythrocytes. The immunoreactivity of the intraventricular macrophages was noticeably enhanced with the monoclonal antibodies OX-42 and OX-18 which marked the complement type 3 receptors (CR3) and major histocompatibility complex (MHC) class I antigen, respectively. Many immunoreactive cells with similar external morphology were observed to penetrate the ependymal lining at the roof of the ventricles. This, coupled with the concomitant depletion of the conglomeration of amoeboid microglia in the supraventricular corpus callosum, suggests that the upsurge of immunoreactive intraventricular macrophages in hydrocephalus was partly due to the influx of amoeboid microglia probably in response to the damage of the ventricular walls and possible alteration in the contents of the cerebrospinal fluid. The significance of the upregulation of complement type 3 receptors and major histocompatibility complex class I antigens on epiplexus cells in hydrocephalic rats remains to be explored, although our results suggest that the surface antigens may be involved in increased phagocytosis and/or a possible immune response.

Peripheral immune response in albino rats following cerebroventricular and intraperitoneal antigen challenge

Success in neural tissue transplants at central nervous system suggest that the site may be immunologically privileged. However, this experimental study in which an antigen (Sheep Red Blood Cells) was administered into the third ventricle does not support the above concept. The antibody titre and soluble immune complex levels seen in these animals are similar to the levels seen in animals immunized with the same amount of antigen through the intraperitoneal route. Intraventricular immunization is rather a more potent modulator in decreasing the total WBC count (P < 0.05) and neutrophils (P < 0.001). Further a marked increase in lymphocytes (P < 0.01) in peripheral blood was observed in these animals. Intraventricular immunization also increased the killing power (NBT reduction) of the neutrophils (P < 0.05).

Differences between ventricular and lumbar cerebrospinal fluid in hydrocephalus secondary to cysticercosis

We studied ventricular and lumbar cerebrospinal fluid (CSF) in 16 patients with hydrocephalus secondary to meningeal cysticercosis, and samples were taken at the time of the surgical implantation of a ventricular shunt. All lumbar CSF samples revealed raised cell counts (mean, 72 +/- 28/mm3) and protein counts (mean, 78 +/- 12 mg/dl), as well as positive immune reactions to cysticerci antigens. In contrast, 50% of the ventricular CSF samples exhibited cell and protein counts within normal limits and five showed negative immune reactions to cysticerci antigens. Ample differences between ventricular and lumbar CSF were also observed in the contents of glucose and immunoglobulins G, A, and M. The biochemical and immunological composition of the CSF varied greatly along the cerebrospinal axis in patients with chronic arachnoiditis caused by cysticercosis. Our findings further support the premise of the subarachnoid space as an immunologically active substratum and provide information to explain the frequent occlusion of ventricular shunts in patients with hydrocephalus secondary to inflammatory disorders of the subarachnoid space.

Allografts of CNS tissue possess a blood-brain barrier: III. Neuropathological, methodological, and immunological considerations

Development of a blood-brain barrier (BBB) within mammalian CNS grafts, placed either intracerebrally or peripherally, has been controversial. Published data from this laboratory have emphasized the presence or the absence of a BBB within solid mammalian tissue or cell suspension grafts is determined intrinsically by the graft and not by the surrounding host parenchyma (e.g., brain, kidney, testis, etc.). Nevertheless, correctly interpreting whether or not a BBB exists within brain grafts is manifested by methodologies employed to answer the question and by ensuing neuropathological and immunological consequences of intracerebral grafting. The present study addresses these issues and suggests misinterpretation for the absence of a BBB in brain grafts can be attributed to: (1) rupture of interendothelial tight junctional complexes in vessels of CNS grafts fixed by perfusion of the host; (2) damage to host vessels and BBB during the intracerebral grafting procedure; (3) graft placement in proximity to inherently permeable vessels (e.g., CNS sites lying outside the BBB) supplying the subarachnoid space/pial surface and circumventricular organs such as the median eminence, area postrema, and choroid plexus; and (4) graft rejection associated with antigen presenting cells and the host immune response. The latter is prevalent in xenogeneic grafts and exists in allogeneic grafts with donor-host mismatch in the major and/or minor histocompatibility complex. CNS grafts between non-immunosuppressed outbred donor and host rats of the same strain (e.g., Sprague Dawley or Wistar rats) can be rejected by the host; these grafts exhibit populations of immunohistochemically identifiable major histocompatibility complex class I+ and class EE+ cells (microglia, macrophages, etc.) and CD4+ T-helper and CD8+ T-cytotoxic lymphocytes. PC12 cell suspension grafts placed within the CNS of non-immunosuppressed Sprague Dawley rats are rejected similarly. Donor cells from solid CNS grafts placed intracerebrally and stained immunohistochemically for donor major histocompatibility complex (MHC) class I expression are identified within the host spleen and lymph nodes; these donor MHC expressing cells may initiate the host immune response subsequent to the cells entering the general circulation through host cerebral vessels damaged during graft placement. Rapid healing of damaged cerebral vessels is stimulated with exogenously applied basic fibroblast growth factor, which may prove helpful in reducing the potential entry of donor cells to the host circulation. These results have implication clinically for the intracerebral grafting of human fetal CNS cell suspensions.

Brain structure changes in schizophrenics with high serum titers of antibodies to herpes virus

We compared five indices of brain structure between two groups of schizophrenics, namely, those with high and normal levels of antibody in the serum to herpes virus. Eleven 'immuno-positive' and 21 'immuno-normal' subjects obtained from a concomitant study of serum IgG antibody to viruses underwent magnetic resonance imaging (MRI) utilizing a 1 Tesla magnet and 8 mm thick slices. We measured ventricle-brain ratio (VBR), 3rd ventricle width, cortical atrophy, area of corpus callosum, and frontal lobe area. The differences between groups were assessed by t-test and chi-square analysis. Eight of 11 immuno-positives compared to 7 of 21 immuno-normals showed evidence of cortical atrophy (chi 2 = 4.49, p < 0.03). The immuno-positives had smaller left frontal area (mean + s.d = 125.69 + 21.30 versus 143.76 + 19.84, t = 2.07, p < 0.05) and larger 2nd quadrant of the corpus callosum (mean + s.d. = 1.58 + 0.39 versus 1.27 + 0.52, t = 2.68, p < 0.01). The right frontal area also was smaller in immuno-positives but not significant. VBR, 3rd ventricle and the 1st, 3rd and 4th callosal quadrants did not differ between the groups. We conclude that high antibody titers to herpes found in the sera of some schizophrenics might reflect an earlier pathogenetic process that affected brain development. Further studies of antibodies in CSF and brain structure in these or similar subjects and those suspected to be exposed to viral infections in utero should be vigorously pursued to obtain definitive evidence for this hypothesis.

The role of Mycobacterium tuberculosis in experimental allergic encephalomyelitis

Various detergents used in preparative membrane protein chemistry were added to a complete Freund's adjuvant/water emulsion in order to increase the solubility and/or immunologic availability of the Mycobacterium tuberculosis membrane and to explain its role in blood-brain barrier (BBB) permeability. Magnetic resonance imaging was used for in vivo determination of the BBB breakdown and cerebral edema. The results showed that with 1% 10 tridecyl ether, which increases emulsion stability, abundant BBB breakdown and cerebral edema were observed, similar to those encountered in experimental allergic encephalomyelitis (EAE). We suggest that the immunologic response triggered off by M. tuberculosis largely contributes to the BBB permeability changes observed during EAE, probably by an action on the endothelial cells of the cerebral blood vessels.

Immunosuppression by morphine is mediated by central pathways

We reported previously that a single systemic injection of morphine (10 mg/kg) to rats profoundly suppressed mitogen-induced proliferation of blood lymphocytes by a receptor-mediated mechanism. The present study examined whether this immunosuppressive effect of morphine is mediated by opioid receptors located at either peripheral or central sites. First, the effects of systemic morphine administration on analgesia, mitogen-stimulated lymphocyte proliferation and corticosterone secretion were compared to those observed after the systemic administration of N-methylmorphine, a quaternary derivative which does not readily penetrate the blood-brain barrier. In contrast to systemically administered morphine, the i.p. injection of N-methyl-morphine (20 mg/kg) was without any effect on lymphocyte proliferation, plasma corticosterone concentrations or analgesic responses. Secondly, the effects of morphine and N-methylmorphine after central administration were compared. Within 2 hr after the microinjection of either morphine (10 micrograms/2 microliters) or N-methylmorphine (15 micrograms/2 microliters) into the third ventricle, blood lymphocyte responses were inhibited by 70%, plasma corticosterone concentrations were significantly elevated and maximal analgesic responses were present. Finally, microinjection of morphine (1 microgram/0.2 microliter) into the anterior hypothalamus inhibited blood lymphocyte proliferation by 50% without producing analgesia or a significant increase in plasma corticosterone. These findings suggest that central opioid pathways are involved in the immunosuppressive effects of morphine and these pathways may be distinct from those participating in opioid-induced analgesia and adrenal activation.

Ovalbumin is more immunogenic when introduced into brain or cerebrospinal fluid than into extracerebral sites

The magnitudes of serum antibody responses to ovalbumin have been compared following immunization via cerebral or extracerebral sites in Sprague-Dawley rats. In central nervous system (CNS)-immunized rats, conditions were designed to ensure normal brain barrier permeability. Extracerebral immunization was via the footpad or along pathways of antigen outflow from the CNS. The relative immunogenicity of different injection sites is: CSF greater than brain tissue greater than extracerebral sites. Enhancement of the antibody response to CNS-administered antigen appears to depend on events initiated within the CNS, since ovalbumin injected into blood (which reaches the spleen) or nasal submucosa (which drains to cervical nodes) fails to elicit a similar response.

Ventricular CSF immunoglobulins in brain tumours

Ventricular CSF glucose, total protein, protein electrophoresis, IgG, IgA, IgM and CSF cytology were determined in thirty seven patients with brain tumours. CSF glucose was unchanged and total protein was significantly high. Protein electrophoresis showed higher albumin and gamma globulin fractions. Mean IgG and IgA were significantly higher (P less than 0.001) in malignant tumours than in benign ones. IgM was detectable in 7 of 37 cases. The higher concentration of total protein, albumin and gamma globulin shows some degree of impairment of blood brain barrier. Increased concentration of IgG, IgA and IgM indicates humoral immune response of the brain against the tumours.

Response of intraventricular macrophages to crotoxin-coated microcarrier beads injected into the lateral ventricle of postnatal rats

Crotoxin-coated microcarrier beads were injected into the lateral ventricles of 5 days old postnatal rats. The morphology of the cells attached to the beads at various time intervals was studied by scanning and transmission electron microscopy. Scanning electron microscopy showed that very few cells were associated with the surface of the beads 18 hours after the injection. After 2 days a large number of spherical cells showing blebs and filopodia were attached to the surface of the beads. One week after the injection, these cells became oval and, in longer survival periods between 2 weeks and 30 days after the injection, the cells developed a flattened or angular cell body bearing a number of radiating slender processes. Transmission electron microscopy of the re-embedded materials from animals killed 2 days after the injection showed many cells with an eccentric nucleus containing dense chromatin masses. Their abundant cytoplasm was endowed with a variable number of lysosome-like dense granules and vacuoles. In longer surviving animals, the cells became elongated with scanty cytoplasm showing relatively fewer dense granules and cytoplasmic vacuoles. It is postulated from this study that the cells attached to the crotoxin-coated beads are derived from the intraventricular macrophages. These are functionally active initially in response to the beads injected. With time, however, they undergo morphological alteration and regress into quiescent cells which are microglia-like.

Monoclonal antibodies identify three IgG Fc receptors in normal human central nervous system

Functional Fc receptors have been described in the central nervous system (CNS) in the subependymal periventricular regions, leptomeninges, including brain perivascular tissues, and choroid plexus. The distribution of this receptor activity suggests a role in protection of adjacent nervous tissue from IgG-opsonized antigens, including microorganisms. In this report, we have utilized monoclonal antibodies to human Fc gamma RI, II, and III; 32, IV.3, and 3G8, respectively, to immunohistochemically examine the distribution of these receptors in the CNS. Fc gamma RI was only occasionally present in the CNS where it was identified most often in the choroid plexus. Fc gamma RII was the predominant receptor in brain. It as consistently present in leptomeninges, including brain perivascular regions, arachnoid granulations, and choroid plexus stroma. Some samples of subependymal periventricular tissue also displayed Fc gamma RII. Fc gamma RIII was only identified in subependymal periventricular tissue but not in choroid plexus and arachnoid. These results demonstrate that regions of normal adult brain which produce cerebral spinal fluid (CSF) and border on CSF and vascular compartments display Fc gamma R heterogeneity consistent with that of blood monocytes and systemic macrophages.

Expression of Ia antigen on vascular endothelial cells in mouse cerebral tissue grafted into the third ventricle of rat brain

The mechanisms of the immunological rejection after xenogeneic neural transplantation were investigated with special reference to the expression of class II major histocompatibility complex (MHC) antigen (Ia antigen) on the grafted tissue. Tissue from a newborn mouse cerebral cortex was transplanted into the third ventricle of a 4-week-old rat brain. Infiltration of cytotoxic T-cells into the grafted tissue was investigated immunohistochemically by using a monoclonal antibody (OX-8). The infiltration began 8 days after transplantation and continued until about 4 weeks when the tissue was completely rejected. The expression of Ia antigen was also investigated immunohistochemically. The Ia antigen was first detected in the grafted tissue at 6 days after transplantation. The Ia antigen was considered to be expressed on the vascular endothelial cells judging from the staining patterns and the location of India ink which was perfused from the host's left cardiac ventricle. The perfusion experiments with India ink also revealed that blood was supplied to the grafted tissue from 5 days after transplantation. These results suggest that the expression of Ia antigen on the vascular endothelial cells renders the grafted tissues competent to initiate and participate in the immune reaction. The results also raise a possibility that the expression of Ia antigen is triggered by blood supplied from the host brain. In addition, the results indicate that the Ia-positive blood vessels do not originate in the host brain but are intrinsic to the grafted tissue.

Immune response in draining lymph nodes and spleen after intraventricular injection of antigen

Both Fischer 344 and Sprague Dawley rats showed significant numbers of antibody forming cells (PFC) in deep cervical lymph nodes after intraventricular injection of antigens, including trinitrophenylated (TNP)-hemocyanin, TNP-B. abortus and sheep erythrocytes. This indicated that particular as well as soluble antigens drained to these lymph nodes from the spinal fluid. Other lymph nodes examined did not show increased PFC over background, but levels of PFC in the spleen were significantly elevated after intraventricular injection of each of these antigens. Comparison with dose responses in the spleen after intravenous antigen injection suggested that approximately 20% of the intraventricularly injected immunogens drained to the peripheral blood. The relevance of these findings with respect to the brain as an immunologically privileged site is discussed.

Rejection of fetal neocortical neural transplants by H-2 incompatible mice

In order to examine questions concerning immunologic privilege of the central nervous system, we placed neocortical transplants into cerebral ventricles of mice. We compared the fates of transplants between fully H-2 compatible (isografts) and H-2 incompatible (allografts) animals. Histologic evaluation comparing animals from iso- and allograft groups revealed significant differences in the number of inflammatory cells and in the degree of necrosis within the grafts. Response to allografted tissue within the brain mimics that seen in several immune-mediated diseases of the nervous system in that neurons appear to be selectively spared. Only upon subsequent stimulation of the host's immune system with an orthotopic skin graft bearing the major histocompatibility complex antigens of the neural graft are neurons destroyed. Immunohistochemical evaluation revealed that the inflammatory cell infiltrates in and around the allografts were composed of Lyt-2+, L3T4+, and Mac-1+ cells. In addition, Ia+ endothelial cells as well as Ia+ parenchymal CNS cells were found in both donor and host tissue of allografted animals. Hence, H-2 incompatible neural tissue transplanted to the CNS is recognized and rejected by the immune system of the recipient animal. The cellular infiltrates seen within the first weeks to months following transplantation of allogeneic CNS tissue resemble those seen in other allografts undergoing rejection. We conclude that the CNS is not unconditionally privileged as either a transplant site or as a source of transplanted tissue.

Functional brain tissue transplantation: reversal of lesion-induced rotation by intraventricular substantia nigra and adrenal medulla grafts, with a note on intracranial retinal grafts

Using a rotational behavior animal model, it has been found that embryonic substantia nigra (SN) can be homologously transplanted to the brain lateral ventricles to reverse the effects of SN lesions. These grafts were found to decrease the lesion-induced rotational behavior that was provoked either by apomorphine or amphetamine. This effect was not duplicated by grafts of other embryonic brain regions. The SN grafts produced a dopaminergic reinnervation of the dorsomedial striatum that appeared to be responsible for the behavioral amelioration. Long-term studies demonstrated that behavioral efficacy and survival continued for at least 6 months to 1 1/2 years. The catecholaminergic "chromaffin" cells of the adrenal medulla possess a remarkable ability to change morphologically and biochemically in response to their environmental hormonal milieu. This plasticity was exploited by transplanting adrenal medulla to the rat brain to reverse the effects of SN lesions. This tissue changed biochemically by producing large amounts of dopamine, and morphologically, by extending coarse fiber processes. Although these grafts appeared to secrete catecholamines, they did not reinnervate the striatum. Rotational behavior was reduced by these grafts, apparently as a consequence of the catecholamine secretion. When adrenal chromaffin tissue was obtained from 1- or 2-year-old donors, however, lesion-induced rotational behavior was not reduced. It is suggested that adrenal chromaffin cell grafts from young donors possess a biochemical plasticity that is the basis for the behavioral effect, but that this plasticity is lost with maturity of the tissue. An important issue for future applications of these procedures is the immunological privilege of the brain lateral ventricles. We found that both embryonic brain tissue and adult adrenal medulla "allografts" from Brown Norway rat donors consistently survived for at least 6 months in the ventricles of Fisher 344-strain rat hosts. These strains differ in major histocompatibility antigens and, as expected, Fisher 344 rats rapidly rejected Brown Norway skin grafts. Skin graft survival times were not influenced by the presence of established brain grafts, nor did brain grafts elicit systemic humoral immunity. Conversely, however, independent elicitation of systemic immunity by skin grafting resulted in the rejection of long-established brain grafts concomitant with rejection of the skin grafts. Rotational behavior in Fisher 344 hosts was reduced by brain grafts from Brown Norway donors; yet, after rotation had been reduced it could be brought back to baseline levels through systemic immunization and associated brain graft rejection.(ABSTRACT TRUNCATED AT 400 WORDS)

Prolonged survival of bovine adrenal chromaffin cells in rat cerebral ventricles

Dispersed, cultured bovine adrenal chromaffin cells transplanted into the cerebral ventricles of neonatal and adult rats survived at least 2 mo without evidence of immunological rejection. The cells can be identified by their strong yellow fluorescent reaction with glyoxylic acid, which suggests that they maintain intact the capability of synthesizing and storing catecholamines. The cells did not show sprouting or process formation and appeared to be free in the ventricle or aggregated in clusters. This shows that cells from different animal species and from different tissue origins can be transplanted and can survive in the cerebral ventricles.

Alterations of immunoreactive beta-endorphin in the third ventricular fluid in response to electrical stimulation of the human periaqueductal gray matter

Immunoreactive beta-endorphin in the third ventricular fluid was measured in response to electrical stimulation of the periaqueductal gray matter in 8 patients with intractable pain during rostral mesencephalic reticulotomy for pain relief. In all patients, marked increase of immunoreactive beta-endorphin was observed. On the other hand, in cases of electrical stimulation of the zona incerta performed during stereoencephalotomy, in 5 patients with involuntary movement, immunoreactive beta-endorphin in the third ventricular fluid did not show any significant change. The authors conclude that the increase of immunoreactive beta-endorphin on electrical stimulation of the periaqueductal gray matter is not a nonspecific response to brain stimulation but a specific response in regard to cerebral localization of endorphins. Direct correlation between pain relief and periaqueductal gray stimulation is also questioned.