Acute experimental autoimmune encephalomyelitis: T- and B-cell distribution within the target organ

Autoaggressive effector T cells in the course of experimental autoimmune encephalomyelitis visualized in the light of two-photon microscopy

Two photon microscopy (TPM) recently emerged as optical tool for the visualization of immune processes hundreds of micrometers deep in living tissue and organs. Here we summarize recent work on exploiting this technology to study brain antigen specific T cells. These cells are the cause of Experimental Autoimmune Encephalomyelitis (EAE) an autoimmune disease model of Multiple Sclerosis. TPM studies elucidated the dynamics of the autoaggressive effector T cells in peripheral immune milieus during preclinical EAE, where the cells become reprogrammed to enter their target organ. These studies revealed an unexpectedly lively locomotion behavior of the cells interrupted only by short-lasting contacts with the local immune stroma. Live T cell behavior was furthermore studied within the acutely inflamed CNS. Two distinct migratory patterns of the T cells were found: the majority of cells (60-70%) moved fast and seemingly unhindered through the compact CNS parenchyma. The motility of the other cell fraction was highly confined. The cells swung around a fixed cell pole forming long-lasting contacts to putative local antigen presenting cells.

Time course of biochemical and immunohistological alterations during experimental allergic encephalomyelitis

A comprehensive biochemical, immunological and histological study was undertaken during different stages of experimental allergic encephalomyelitis (EAE). Wistar rats with EAE induced by sensitization with bovine myelin showed a maximum decrease of body weight 14-16 days post-inoculation (dpi), coincident with the appearance of the paralysis symptom (acute period). Quantitation of some brain components indicated a temporal dissociation among the alterations observed. The higher diminution of myelin basic protein (MBP) occurred at 6 dpi and then increased to reach 21 dpi, a normal value. Also, the activity of 2',3'-cyclic nucleotide 3'-phosphohydrolase was reduced by 40% with respect to control animals only at 6 dpi. The total lipid content was normal; however, among the individual lipids, sulfatides were principally degraded during the acute stage but the amount of cerebrosides was decreased during the recovery period (29-40 dpi). Free cholesterol was similar in both groups of animals, whereas cholesterol esters were detected in EAE animals from 14 to 40 dpi. Central nervous system meningeal and parenchymal infiltration with mononuclear cells was recognized principally at 14 dpi, but some of cells were still present at 40 dpi. Deposits of immunoglobulins in the infiltrated regions as well as in spinal cord motor neurons were observed among 14-29 dpi. Total circulating antibodies to MBP began to increase at 14 dpi, reaching a plateau at 21 dpi and then maintaining this value until 40 dpi. However, the population of anti-MBP antibodies that also recognizes the neuronal protein synapsin was only present at 14 dpi. The present results suggest that the neurological symptoms can be related to some early changes in the myelin membrane followed by alterations involving neuronal structures. The existence of immunological factors against some epitopes in MBP that also recognize a synaptosomal protein might account, at least in part, for the axonal damage and disruption of the normal interneuronal activity in EAE and lead together with the alterations in some specific myelin constituents and the concomitant CNS inflammatory process to the observed hindlimb paralysis.

Expression of CD45RC and Ia antigen in the spinal cord in acute experimental allergic encephalomyelitis: an immunocytochemical and flow cytometric study

We performed immunocytochemical studies to analyze the inflammatory infiltrate and major histocompatibility complex class II (Ia) antigen expression in the spinal cord of Lewis rats with acute experimental allergic encephalomyelitis (EAE) induced by inoculation with myelin basic protein and adjuvants. Using antibodies to lymphocyte markers and other monoclonal antibodies we found that during clinical episodes the inflammatory infiltrate was chiefly composed of T lymphocytes and macrophages. The majority of cells in the inflammatory infiltrate were stained by the W3/25 antibody to CD4 and a proportion was stained by OX22 which labels the high molecular weight form of the leucocyte common antigen (CD45RC). CD8+ T cells were sparse and B cells were not detected. There was minimal staining with the OX39 antibody to the interleukin-2 receptor. Presumptive microglia, identified by their dendritic morphology, expressed Ia antigen during the clinical episodes and after recovery. The prominence of Ia antigen expression after recovery could indicate that this Ia expression was associated with downregulation of the encephalitogenic immune response. We also performed flow cytometry studies on cells extracted from the spinal cord of rats before and during attacks of EAE. With flow cytometry, we found that in established disease a mean of 83(SD, 23)% of CD2+ cells were CD4+, and a mean of 27(SD, 12)% of CD2+ cells were CD45RC+. In rats sampled on the first day of signs, a mean of 43(SD, 22)% of CD2+ cells were CD45RC+. In the cells extracted from the spinal cord of rats with established disease a mean of 47(SD, 32)% of macrophages were CD45RC+. Our study has combined an immunocytochemical assessment of tissue sections with quantitative flow cytometry assessment of cells extracted from the spinal cord of rats with acute EAE. We have shown that the majority of T lymphocytes in the spinal cord are CD45RC-. We have also found prominent Ia expression on dendritic cells in acute EAE and after clinical recovery.

A quantitative immunocytochemical study of the infiltrating lymphocytes in the spinal cord of guinea pigs with chronic relapsing experimental allergic encephalomyelitis

The production and characterization of an anti-guinea pig B cell monoclonal antibody is described. Immunocytochemical techniques using this antibody and others recognizing a Pan T cell antigen and T cell subsets were employed to study frozen sections of spinal cord from guinea pigs with chronic relapsing experimental allergic encephalomyelitis. T and B cells were found in both perivascular lesions and the central nervous system parenchyma, with the major T cell infiltration occurring by the end of the acute phase of disease. The distribution of T cell subsets suggests a phenotypic selectivity in favour of the transport of CT6 (putative CD8)+ve cells across the blood-brain barrier.

Isolation and characterization of brain macrophages from the central nervous system of newborn and adult rats and of rats with experimental allergic encephalomyelitis

A method has been developed to isolate brain macrophages (M phi) from normal neonatal and adult rats brain cell suspensions, as well as from brain cell suspensions of rat with experimental allergic encephalomyelitis (EAE), by making use of the ability of M phi to adhere to plastic surfaces. The isolated adherent cells were immuno- and enzyme-cytochemically identified. Phagocytic activity and the presence of Fc-IgG receptors were also examined. Approximately 30%-40% of the isolated adherent cells from neonatal rat brain are phagocytic and can be stained with macrophage-specific monoclonal antibodies, suggesting that these cells belong to the monocyte/macrophage lineage. From normal adult rat brain, only a small number of brain M phi could be isolated. A highly purified population of brain M phi was obtained from EAE rat brain. The isolated brain M phi are phagocytic, possess Fc-IgG receptors and rat M phi-associated antigens. Besides these features, the isolated brain M phi also express MHC class II antigens (Ia-antigens), which suggests that M phi may be involved in the regulation of immunological disorders of the CNS. The method reported here for rapidly isolating a large number of blood-monocyte-derived brain M phi from neonatal and adult brain allows an investigation of the precise role of M phi in inflammatory diseases of the central nervous system.

Pathophysiological aspects of acute experimental allergic encephalomyelitis

Traditionally, research in experimental allergic encephalomyelitis (EAE) has focussed on immunological and histopathological aspects. The present review introduces a physiological approach to EAE. As EAE is characterized by many small, focal lesions in the central nervous system (CNS), methods with a high spatial resolution should be used to conduct studies on regional pathophysiology in the condition. Quantitative autoradiography seems an ideal method as it offers, 1) high regional resolution (approximately 50 um), 2) precise quantitation and, 3) a direct correlation between regional histopathology and pathophysiology. By the use of this method, the author has performed studies on 1) regional blood-brain barrier (BBB) permeability, and 2) regional metabolism of energy substrate and related subjects, (i.e. regional cerebral blood flow, regional cerebral glucose metabolic rate and regional pH). Corresponding to the EAE lesions (lymphocytic accumulations), there is a considerable increase in BBB permeability. Metabolism of energy substrate at the lesion sites is severely deranged, which is expressed in a CBF/CMR ratio of 3 ml/mumol compared to the normal 1.5 ml/mumol. No changes in regional pH are seen in the lesions. Unrelated to the lesion sites there is a 50% decrease in blood flow in cerebral cortex. This observation probably reflects a functional decrease in cortical flow due to sensory motor impairment.

Autoantibody responses in the cerebrospinal fluid of guinea pigs with chronic relapsing experimental allergic encephalomyelitis

We report the use of the ELISA technique to measure IgG specific for whole cord, myelin, myelin basic protein and Mycobacterium tuberculosis in the cerebrospinal fluid (CSF) of Strain 13 guinea pigs in different stages of chronic relapsing experimental allergic encephalomyelitis (CR-EAE). Specific antibody levels to all 4 antigen preparations were related to the severity of clinical signs, with the highest levels of IgG in the CSF of guinea pigs in relapse or in stable chronic disease. Total IgG levels in the CSF, though elevated throughout the course of CR-EAE, did not show any association with the category of disease. Control animals inoculated with complete Freund's adjuvant (CFA) alone showed CSF IgG levels specific for M. tuberculosis that were not significantly different from those in animals with chronic EAE, indicating that CFA may itself induce a late-acting increase in blood-brain barrier permeability.

Dynamics of IgG+, IgA+, and IgM+ plasma cells in the central nervous system of guinea pigs with chronic relapsing experimental allergic encephalomyelitis

IgG+, IgA+, and IgM+ plasma cells (PC) were investigated by quantitative immunocytochemistry in the central nervous system (CNS) of guinea pigs with chronic relapsing experimental allergic encephalomyelitis (crEAE) and in the CNS of controls. Frequencies of Ig+ PC in crEAE were, on average, 30-130 times higher than in controls. At all stages of crEAE, IgG was the dominant isotype of CNS PC. In the course of crEAE there was an increase in the proportion of IgG+ PC and a decrease in the proportions of IgM+ and, to a lesser extent, of IgA+ PC. Accumulation of IgM+ PC appears to be related to the acuteness of the disease. Our studies also indicate that IgA, in addition to IgG and IgM, is involved in the immunological response of crEAE in the CNS, and demonstrate that the time course of crEAE is characterized by isotype-specific differences in the immune responses of IgG+, IgM+, and IgA+ PC in the CNS.

Limiting dilution analysis of the frequency of antigen-reactive lymphocytes isolated from the central nervous system of Lewis rats with experimental allergic encephalomyelitis

Lymphocytes were isolated from the spinal cord and draining lymph nodes of Lewis rats with acute experimental allergic encephalomyelitis (EAE) 12 days after immunization with myelin basic protein (MBP) and tetanus toxoid (TT). An average of 8.0 +/- 2.0 X 10(6) cells was obtained from the spinal cord. Of these 71.1 +/- 8.6% expressed the helper-T-cell marker W3/25 and 14.8 +/- 6.2% expressed the killer/suppressor-T-cell marker OX8. By limiting dilution analysis of cells exhibiting an antigen-specific proliferative response, the average frequencies of cells reactive to MBP and TT were 3.36 +/- 2.4 and 7.60 +/- 4.1 per 10(4), respectively. In the draining lymph nodes, the frequencies of cells reactive to MBP and TT were 2.24 +/- 1.7 and 2.69 +/- 2.5 per 10(4). At a relatively early stage of clinical EAE, MBP-reactive T cells comprise only a small minority of the cells which can be isolated from the spinal cord; lymphocytes reactive to a protein antigen irrelevant to EAE pathogenesis are present in comparable numbers. This finding suggests that most of these cells accumulate as a result of mechanisms not specific for MBP-reactive lymphocytes.

Extraction and immunocytochemical characterization of viable mononuclear inflammatory cells from brains of mice with chronic Toxoplasma gondii infection

A method which combined mechanical and enzymatic dissociation of brain parenchyma with Percoll density gradient centrifugation of the resulting tissue suspension was developed for the extraction of viable mononuclear inflammatory cells from the brains of mice. This method was used to extract mononuclear inflammatory cells from the brains of normal mice and mice chronically infected with the intracellular parasite Toxoplasma gondii. Infection with T. gondii was found to result in a 5- to 7-fold increase in the number of mononuclear cells which could be extracted from mouse brains. Immunocytochemical characterization of the extracted mononuclear cell fractions using monoclonal antibodies against T cell subsets and monocyte/macrophages revealed that the numbers of helper T cells, cytotoxic/suppressor T cells, and monocyte/macrophages present in mouse brain increased markedly after infection with T. gondii. This method may prove useful in identifying the cells responsible for inhibition of growth of tumor cells in the brain which has been observed after infection with T. gondii in mice.

Transfer of autoimmune encephalomyelitis with T lymphocytes in strain 13 guinea pigs

Experimental autoimmune encephalomyelitis (EAE) and/or tuberculin sensitivity were transferred to histocompatible recipients with myelin basic protein-stimulated and/or PPD stimulated guinea pig lymph node T cells previously separated by depletion of B cells ("panning") on rabbit anti-guinea pig Ig antibody-coated Petri plates. The depletion was augmented by complement-mediated lysis using mouse anti-guinea pig B-cell monoclonal antibody (31D2), rabbit anti-mouse Ig, and rabbit complement. B cells did not transfer EAE nor provide protection against active immunization with guinea pig spinal cord antigen.

Immunohistological analysis of macrophages in the central nervous system of Lewis rats with acute experimental allergic encephalomyelitis

Inflammatory cells were characterized by immunohistochemistry, utilizing monoclonal antibodies specific for T cell subsets, B cells, Ia-positive cells and cells of the mononuclear phagocyte system, in cryostat sections of central nervous system of Lewis rats, sacrificed during the course of actively induced experimental allergic encephalomyelitis. The present study provides interesting information about the presence and distribution of cells of the monocyte-macrophage lineage in this immunologically mediated disease. Using these monoclonal antibodies different subpopulations of macrophages having varying distribution patterns in the central nervous system can be recognized.

Postnatal development of a demyelinating disease in avian spinal cord chimeras

Xenogeneic spinal cord chimeras were constructed by grafting fragments of quail neural primordium into chick embryos at 2 days of incubation. Hatched birds displayed normal motor behavior for about 5 to 7 weeks, whereupon they developed a neurological syndrome; in the grafted spinal cord the pathological signs of the disease were very similar to those of the active plaques of multiple sclerosis and of the lesions of experimental allergic encephalomyelitis and neuritis, including Ia expression by brain capillary endothelia, rupture of the blood-brain barrier, leukocytic infiltration in the nervous tissue, and demyelination. In the animals at the most advanced stage of the disease an autoimmune attack occurred on the host's nervous system with the same histopathological signs.

Dissociation between histological and clinical signs of experimental auto-immune encephalomyelitis

Lewis rats show a rough correlation between clinical score and histological score of auto-immune encephalomyelitis (EAE). When animals with strong and comparable clinical EAE but with different genetic backgrounds are studied four weeks after immunization, they reveal histological changes that vary markedly according to the genetic set-up. When studied at the height of the EAE attack, also rats with a very low histological score at day 28 have marked histological changes. The results indicate that routine evaluation of EAE strength by histology at a time when the rats have recovered from paralysis may give quite misleading results in some rat strains or crosses, even though the method is good for the Lewis rat. It is suggested that the late histological score is more related to the presence of a relapsing EAE than to the disease activity in the first attack.

Quantitative analysis of the cellular constituents of the cerebrospinal fluid in chronic relapsing experimental allergic encephalomyelitis

Cerebrospinal fluid (CSF) was taken from guinea pigs in various stages of chronic relapsing experimental allergic encephalomyelitis (CR-EAE). The leucocytes in CSF samples were counted and subjected to immunocytochemical analysis using monoclonal antibodies selectively recognising guinea pig T cells, macrophages or Ia antigens. The results showed that total leucocyte numbers and the proportion of macrophages in CSF were elevated in the acute phase of CR-EAE but samples of CSF from animals in early relapse did not show a significant elevation in leucocyte count or macrophage content. In addition the level of T cell activation was higher in CSF than in peripheral blood during disease and was highest in the acute and immediately post-acute phases of the CR-EAE.

The distribution of immunoglobulins and albumin in the central nervous system in acute experimental allergic encephalomyelitis

Experimental allergic encephalomyelitis (EAE) was induced in young male Lewis rats. Immunohistochemical visualisation of albumin and IgG in the nervous tissue was performed at intervals after induction. The results were correlated to the histological appearance of the tissue. Albumin appeared in the tissue about day 10, 1-2 days before IgG. Within one day both proteins spread from sharply defined perivascular subpial locations to diffuse distribution throughout the tissue. Cellular inflammation was not seen until 3-4 days after extravasation of proteins. The cells also spread from perivascular locations to a diffuse infiltration of the tissue.

Immunocytochemical identification and quantitation of mononuclear cells in the meninges during the development of chronic relapsing experimental allergic encephalomyelitis (CREAE) in the guinea pig

To investigate the role of mononuclear cells in the meninges at all stages of chronic relapsing experimental allergic encephalomyelitis, juvenile guinea pigs were inoculated with isogeneic spinal cord in Freund's complete adjuvant (FCA) in parallel with animals inoculated with FCA alone as age-matched controls. Cytospins were prepared of the meningeal inflammatory cells obtained by washing the brains of these animals. These cytospins were stained by indirect immunoperoxidase, using a panel of monoclonal antibodies (Mabs) recognizing "activated" macrophages (M phi s), Ia antigen, total T cells and a putatively T-cell-suppressor subset, and an antiserum against immunoglobulins. The inflammatory response was quantitated and the proportions of the different cell types were determined. It was found that the total number of infiltrating cells correlated with the neurological symptoms of the disease. "Activated" M phi s increased significantly during the disease, in line with clinical signs. The expression of the Ia antigen, found on both lymphocytes and M phi s, also appeared to correlate with the disease. There was no increase in putative T-suppressor-cells during remission but there was a significant rise in the proportion of both cells staining with anti-immunoglobulins and plasma cells during relapse.

Acute experimental allergic encephalomyelitis in the mouse: immunopathology of the developing lesion

To investigate the sequence of immunopathologic events during lesion formation in acute experimental allergic encephalomyelitis (EAE), SJL/J mice were inoculated with isogeneic spinal cord in complete Freund's adjuvant (CFA) and with Bordetella pertussis on Days 1 and 3 postinoculation (PI). Mice were sampled at different time points PI and T cells, T-cell subsets. Ia+ cells, Ig+ cells, albumin, and Ig deposits were localized in frozen sections by the avidin-biotin complex (ABC) method and direct fluorescence. Furthermore, samples were stained for Ia antigen, myelin basic protein (MBP), and galactocerebroside (GC) localization on endothelial cells by the ABC technique. Clinical and pathologic observations were correlated with the immunopathologic results. It was found that early in the disease process myelin and Ia-antigens were demonstrable on endothelial cells within the central nervous system (CNS). Simultaneously, damage to the blood-brain barrier was apparent, as indicated by albumin deposits, and small numbers of infiltrating T cells, T-cell subsets, and Ia+ cells were found. With time PI, the density of infiltrating total T cells (Thy-1.2+), helper/inducer (Lyt-1+), and suppressor/cytotoxic (Lyt-2+) T cells increased; Lyt-1+ and Lyt-2+ cells were detectable in meningeal as well as parenchymal infiltrates, while later on, Lyt-1+ cells showed some predilection for the CNS parenchyma and Lyt-2+ cells for meninges. Ia+ cells (B cells, macrophages, activated T cells) were present in small numbers only. Ig+ cells (B cells and macrophages) appeared shortly before onset of signs and persisted in moderate numbers. These results reconfirm the importance of early T-cell involvement for the development of EAE; they might also indicate a secondary role for Ig+ cells and are consistent with the concept that presentation of myelin antigens to T cells might occur locally on Ia-bearing endothelial cells within the CNS.

Inhibition of autoimmune neuropathological process by treatment with an iron-chelating agent

Lewis rats that are primed with guinea pig spinal cord homogenized in complete Freund's adjuvant (GPSCH-CFA) develop overt symptoms of experimental allergic encephalomyelitis (EAE). Treatment with the iron-chelating agent, desferrioxamine B mesylate (DFOM), at various times before the onset of EAE, dramatically suppressed both the severity and duration of disease. When DFOM was administered to rats soon after the development of neurological signs, a rapid recovery occurred, though mild, transient symptoms could be seen approximately 1 wk after withdrawal of the drug. Treatment with DFOM was always accompanied by a diminution of T cell responsiveness on the part of the delayed-type hypersensitivity/helper subset and, on histological examination, an absence of inflammatory cells from lesions. Iron is believed to influence both the migration and function of immune effector cells. It can also act as a catalyst in the formation of free radicals, which are highly toxic agents causing tissue damage in sites of inflammation. The mechanisms underlying the effect of DFOM on the severity of EAE, and the possible implications for treatment of multiple sclerosis are discussed.

Chronic experimental allergic encephalomyelitis in guinea pigs: immunologic studies on the two major myelin proteins

Humoral and cell-mediated immunity to the two major myelin proteins, basic protein (MBP) and proteolipid protein, have been investigated during the course of chronic experimental allergic encephalomyelitis (EAE) induced in guinea pigs with whole neural tissue. A positive proliferative response to MBP was observed at 10 and 13 days postimmunization, but was not detectable at subsequent stages. Serum antibodies to MBP first appeared during the chronic stages of the disease. A proliferative response to proteolipid apoprotein was not detected during any stage of chronic EAE. Guinea pigs immunized with proteolipid alone, however, showed a proliferative response. The data suggest that MBP is one of the antigens involved in the induction of the acute episode of chronic EAE, but its role in later stages and that of proteolipid protein remain unknown.

Prostaglandin and thromboxane levels in central nervous system tissues from rats during the induction and development of experimental allergic encephalomyelitis (EAE)

Prostaglandin (PG) and thromboxane levels were measured in the spinal cords and cerebellums of rats during the induction, disease and recovery periods of experimental allergic encephalomyelitis (EAE). In spinal cords PGE and 6-oxo-PGF1 alpha increased to maximum with the onset of neurological symptoms, 11-12 days after inoculation. However, the levels returned to normal at the height of clinical disease, despite the persistence of inflammatory lesions. After an initial fall, PGF2 alpha increased to normal limits, 11-12 days after inoculation, and remained at this level throughout the experiment. In contrast, the cerebellum content of all the eicosanoids decreased prior to the appearance of clinical EAE. PGF2 alpha and 6-oxo-PGF1 alpha concentrations subsequently increased but the PGE and thromboxane levels remained depressed for the duration of the study. The role of the eicosanoids in modulating the immune response to neuroantigen is discussed together with our recent findings in guinea pigs with acute EAE.

A longitudinal study of the prostaglandin content of central nervous system tissues from guinea pigs with acute experimental allergic encephalomyelitis (EAE)

The levels of prostaglandins (PGs) E, F2 alpha and 6-oxo-PGF1 alpha, in spinal cords and cerebellums of guinea pigs were measured during the development of experimental allergic encephalomyelitis (EAE). The earliest change observed was an elevation of PGE in spinal cords, but not cerebellums , 5-7 days post-inoculation (PI) and prior to the appearance of clinical symptoms. PGE content of spinal cords continued to rise until days 12-14 PI when the animals displayed paralytic EAE. In contrast, PGF2 alpha and 6-oxo-PGF1 alpha levels in spinal cords peaked on days 9-11, when the animals exhibited initial clinical signs, but fell to lower values by days 12-14 PI. In cerebellums , the PGE content increased more slowly than in spinal cords, consistent with the lower numbers of mononuclear cell infiltrates, whereas PGF2 alpha and 6-oxo-PGF1 alpha levels remained unaltered. The relationships between the observed changes in prostanoid levels, lesion development and the appearance of clinical symptoms are discussed.

Chronic relapsing experimental allergic encephalomyelitis. The presence in the cerebrospinal fluid of factors chemotactic for monocytes

Cerebrospinal fluid (CSF) was removed from guinea pigs with chronic relapsing experimental allergic encephalomyelitis (CR-EAE) and control inoculated animals by puncture of the cisterna magna. The fluid from 7/8 animals in relapse and 2/4 animals in remission phases of CR-EAE was found to promote the migration of peripheral blood monocytes through a 5-micron pore diameter polycarbonate membrane filter. Monocytes were also found to orient towards the migration-stimulating CSF in a gradient formed between such fluid and CSF derived from a control animal, thereby indicating the presence of a chemotactic factor. The factor responsible for promoting monocyte migration had a molecular weight of between 50 000 and 300 000 as defined by ultrafiltration. The results are discussed in relation to the known pathohistological features of the chronic relapsing disease.