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M P Pender

Publications and source records attributed to M P Pender.

At least 55 records · Page 3Linked to original sources
PubMed1995

The proximal peripheral nervous system is a major site of demyelination in experimental autoimmune encephalomyelitis induced in the Lewis rat by a myelin basic protein-specific T cell clone.

Experimental autoimmune encephalomyelitis (EAE) was induced in the Lewis rat by the passive transfer of a cytotoxic CD4+ T cell clone specific for the 72-89 peptide of guinea-pig myelin basic protein (MBP). Histological studies on rats with neurological signs showed that inflammation was present in the proximal peripheral nervous system (PNS), namely the spinal roots, as well as in the central nervous system (CNS). The main sites of demyelination were the spinal roots in the PNS, and the spinal cord root entry and exit zones in the CNS. The major involvement of the proximal PNS in autoimmune disease directed at MBP is in marked contrast to EAE induced by immunisation with myelin proteolipid protein, where the inflammation and demyelination are restricted to the CNS. These findings may have implications for the human inflammatory demyelinating diseases including multiple sclerosis, in which MBP is a putative target antigen.

Animals↗
PubMed1995

Antigen-specific down-regulation of myelin basic protein-reactive T cells during spontaneous recovery from experimental autoimmune encephalomyelitis: further evidence of apoptotic deletion of autoreactive T cells in the central nervous system.

Experimental autoimmune encephalomyelitis (EAE) was induced in Lewis rats by the i.v. injection of 10(7) cloned V beta 8.2+ T cells specific for the 72-89 peptide of guinea pig myelin basic protein (MBP). Some animals were injected simultaneously with 10(7) cloned T cells specific for ovalbumin (OVA). Lymphocytes were isolated from the spinal cord and from the peripheral lymphoid organs of these rats and the frequencies of MBP-peptide-specific or OVA-specific proliferating cells were estimated by limiting dilution analysis at different times after cell transfer. The frequencies of cells specific for MBP72-89 or OVA in the spinal cord were highest 5 days after cell transfer (MBP72-89, 1 in 1149; OVA, 1 in 1116). On day 7, when the rats were recovering, the frequency of cells specific for MBP72-89 in the spinal cord fell dramatically to < 1 in 10(5), while that of OVA-specific cells decreased to a much lesser extent (1 in 7001). The frequencies of MBP72-89-specific cells in the peripheral lymphoid organs during and after recovery were also much lower than those of OVA-specific cells. A similar pattern of down-regulation of the MBP-peptide-specific, but not the OVA-specific, T cell response was observed in the spleen and mesenteric lymph nodes (MLN) of rats 38 days after the active induction of EAE by immunization with equal amounts of MBP and OVA in adjuvants. In the passively transferred model, cells isolated from the spinal cord and MLN on day 7 did not regain responsiveness to MBP72-89 after incubation with high levels of IL-2, indicating that the unresponsiveness was not due to T cell anergy. Thus this study demonstrates that there is a specific down-regulation of the MBP72-89-specific T cell response during spontaneous recovery from EAE.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Apoptotic elimination of V beta 8.2+ cells from the central nervous system during recovery from experimental autoimmune encephalomyelitis induced by the passive transfer of V beta 8.2+ encephalitogenic T cells.

A CD4+V beta 8.2+ T cell clone specific for the peptide 72-89 of guinea pig myelin basic protein (GMBP) was used to induce acute experimental autoimmune encephalomyelitis (EAE) in Lewis rats. To assess apoptosis in inflammatory cells infiltrating the central nervous system (CNS), we extracted cells from the spinal cord, enriched them for T cells and performed flow-cytometric analysis of their DNA stained with propidium iodide. The presence of apoptosis was confirmed by the demonstration of DNA fragmentation on gel electrophoresis. A gradual increase in the proportion of apoptotic cells was observed between 4 and 7 days after the transfer of the encephalitogenic T cells. The highest frequency of apoptotic cells (9.2 +/- 1.2%) was observed 7 days after cell transfer, when clinical recovery commenced. Passive transfer of ovalbumin-specific cells resulted in only a background level (0.8%) of apoptosis in the CNS. We conclude that the apoptotic process selectively eliminates autoreactive T cells from the CNS as: (a) there was a selective disappearance of disease-relevant CD5+V beta 8.2+ cells from the CNS during the course of EAE; (b) there was a decrease in the frequency of CNS-infiltrating T cells reactive to the GMBP 72-89 peptide during the course of EAE, and in a standard proliferation assay there was a loss of in vitro reactivity of CNS-infiltrating cells to this peptide, but not to a non-CNS antigen (ovalbumin); (c) simultaneous surface labeling and DNA analysis of CNS-infiltrating cells revealed that the frequency of V beta 8.2+ cells was about sevenfold higher in the apoptotic T cell population than in the normal (non-apoptotic) T cell population; and (d) we were unable to detect recirculation of the V beta 8.2+ cells to lymphoid organs after their frequency decreased in the CNS. The selective apoptotic elimination of autoreactive T cells from the target organ of this spontaneously resolving autoimmune disease may have implications for the understanding of the mechanism by which an autoimmune attack is terminated and for the design of therapeutic strategies to facilitate this process.

Animals↗
PubMed1994

Macrophage apoptosis in the central nervous system in experimental autoimmune encephalomyelitis.

Using light and electron microscopy, we have demonstrated that macrophage apoptosis (programmed cell death) occurs in the central nervous system (CNS) in Lewis rats with acute experimental autoimmune encephalomyelitis (EAE) and chronic relapsing EAE. Apoptotic macrophages were identified by the presence of an apoptotic nucleus in a cell with cytoplasm containing myelin debris but no intermediate filaments. They were found in the meninges, perivascular spaces and in the parenchyma of the white and grey matter of the spinal cord. In acute EAE the apoptotic macrophages were most frequently seen at the time of maximal neurological signs and during the early stages of clinical recovery. Several possible mechanisms may be responsible for the macrophage apoptosis: the release or withdrawal of cytokines; T-cell cytotoxicity; the effect of activated macrophage products, such as nitric oxide; and a direct effect of endogenous glucocorticoids. Macrophage apoptosis, together with the T-cell apoptosis we have previously described in the CNS in EAE, may contribute to the down-regulation of this autoimmune disease.

Acute Disease↗
PubMed1994

Clinical and histological findings in proteolipid protein-induced experimental autoimmune encephalomyelitis (EAE) in the Lewis rat. Distribution of demyelination differs from that in EAE induced by other antigens.

Proteolipid protein (PLP) is the major protein of central nervous system (CNS) myelin. In some species, intradermal inoculation with PLP and adjuvants causes experimental autoimmune encephalomyelitis (PLP-EAE) characterized by neurological signs of tail and limb weakness and by inflammation and demyelination in the CNS. A previous study found that inoculation of Lewis rats with 100 micrograms of PLP causes PLP-EAE with a low incidence of neurological signs and a highly variable clinical course. In the present study we assessed PLP-EAE produced by inoculation with 1000 micrograms of PLP per rat. Fifty-one of 59 (86%) Lewis rats developed neurological signs 8 to 20 days (mean = 12.0 +/- 2.0) after inoculation with 1000 micrograms of PLP. In such rats, mononuclear cell infiltrates were present in the brain and spinal cord while primary demyelination occurred mainly in the subpial regions of the spinal cord, especially in the dorsal root entry and ventral root exit zones. The histological findings were compared with those in acute EAE induced in the Lewis rat by inoculation with whole CNS tissue or with myelin basic protein: in PLP-EAE, in contrast to these other models, the disease was essentially restricted to the CNS. This form of EAE should be useful in future studies of the consequences of autoimmunity to PLP.

Animals↗
PubMed1994

Inflammatory cells, microglia and MHC class II antigen-positive cells in the spinal cord of Lewis rats with acute and chronic relapsing experimental autoimmune encephalomyelitis.

Chronic relapsing experimental autoimmune encephalomyelitis (CR-EAE) was induced in Lewis rats by inoculation with guinea pig spinal cord and adjuvants and treatment with low dose cyclosporin A (CsA). Acute EAE was induced by the same method without CsA treatment. Immunocytochemistry and flow cytometry were used to assess inflammatory cells and MHC class II (Ia) antigen expression in the central nervous system of these rats. The inflammatory infiltrate was composed mainly of CD4+ T cells and macrophages, and alpha beta T cells constituted about 65% of the CD2+ T cells. After recovery from acute EAE and during the first remission of CR-EAE, the number of T cells was significantly less than in the preceding episodes. The number of T cells was higher in the second episode of CR-EAE than in the first remission. Throughout the course of CR-EAE, the majority of the CD2+ T cells were CD45RC-. The ratio of IL-2R+ cells to CD2+ cells ranged from 10.5 to 24.0%. The ratio of CD4+ T cells to B cells was lower in the later episodes of CR-EAE than in the first episode. Ia antigen was expressed on infiltrating round cells at all stages of CR-EAE and on microglial cells (identified by dendritic morphology) with increasing intensity throughout the course of CR-EAE. With flow cytometry, the number of Ia+ cells obtained from the spinal cord rose throughout the course of CR-EAE. The number of FSClowOX1low cells, which we consider represent microglia, also increased during the course of CR-EAE.

Acute Disease↗
PubMed1994

Conduction abnormalities are restricted to the central nervous system in experimental autoimmune encephalomyelitis induced by inoculation with proteolipid protein but not with myelin basic protein.

Experimental autoimmune encephalomyelitis (EAE) is an inflammatory demyelinating disease of the central nervous system (CNS) and can be induced by inoculation of animals with homogenized CNS tissue or highly purified myelin proteins such as myelin basic protein (MBP) or proteolipid protein (PLP). It is widely studied as a possible animal model of multiple sclerosis. We performed the present neurophysiological study to define the location of nerve conduction abnormalities in EAE induced by immunization with PLP (PLP-EAE) and in EAE induced by immunization with MBP (MBP-EAE) in the Lewis rat. In rats with tail weakness due to acute PLP-EAE, conduction was normal in the spinal nerve roots and peripheral nerves but there was evidence of conduction block in a high proportion of the fibres in the dorsal columns of the lumbosacral spinal cord. In contrast, in acute MBP-EAE, there was conduction block in a high proportion of fibres in the sacral dorsal and ventral roots of the peripheral nervous system (PNS) and in the dorsal columns of the lumbosacral spinal cord. The distribution of nerve conduction abnormalities is consistent with previous histological studies showing that inflammation and primary demyelination are restricted to the CNS in PLP-EAE, but are present in the CNS and in the spinal roots of the PNS in MBP-EAE. The restriction of functional abnormalities to the CNS in PLP-EAE but not in MBP-EAE may have implications for the human inflammatory demyelinating diseases, including multiple sclerosis.

Action Potentials↗
PubMed1992

Focal conduction block in the dorsal root ganglion in experimental allergic neuritis.

Acute experimental allergic neuritis was induced in Lewis rats by inoculation with bovine intradural root myelin and adjuvants. In terminal experiments, sensory conduction was assessed in rats with hindlimb ataxia and weakness by stimulating the exposed sciatic nerve and recording directly from the exposed L-4 spinal nerve, dorsal root ganglion, dorsal root, and dorsal root entry zone. Focal conduction block was present in a high proportion of large-diameter fibers in the dorsal root ganglion. In contrast, nerve conduction in the peripheral nerve and spinal nerve was essentially normal apart from probable conduction block in some fibers in the proximal spinal nerve in a minority of rats. The afferent volley arriving at the dorsal root entry zone of the spinal cord was greatly reduced, as a consequence of the conduction block in the dorsal root ganglion and probable conduction block in the dorsal root. The M wave recorded from the fourth dorsal interosseus muscle of the hindfoot was normal in amplitude but slightly prolonged in latency and the H reflex was absent. These electrophysiological findings correlated well with the histological findings of inflammation and prominent demyelination in the dorsal root ganglia and dorsal roots with minimal involvement of the proximal spinal nerve and no involvement of the sciatic nerve. It is concluded that the hindlimb ataxia in rats with this form of acute experimental allergic neuritis is due to demyelination-induced nerve conduction block in the dorsal root ganglia and probably in the dorsal roots.

Afferent Pathways↗
PubMed1992

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.

Acute Disease↗
PubMed1992

Apoptosis of alpha beta T lymphocytes in the nervous system in experimental autoimmune encephalomyelitis: its possible implications for recovery and acquired tolerance.

We have recently shown that apoptosis, an active process of cellular self-destruction, occurs in the central nervous system in Lewis rats with acute experimental autoimmune encephalomyelitis (EAE) induced by inoculation with myelin basic protein (MBP) and adjuvants. Conventional light and electron microscopic studies suggested that some of the apoptotic cells were oligodendrocytes and that others were hematogenous mononuclear cells. To determine whether any of the apoptotic cells were T lymphocytes, we used the technique of pre-embedding immunolabelling which allows sufficient preservation of the ultrastructure to permit recognition of apoptotic changes while at the same time preserving surface antigens so that the identity of the apoptotic cells can be determined by immunocytochemistry. Light microscopic immunocytochemistry using the monoclonal antibodies OX-34 (CD2) and R73 (alpha beta T-cell receptor) revealed that 10% of the CD2+ cells and 5% of the alpha beta T lymphocytes in the parenchyma of the spinal cord were dying by apoptosis. The presence of apoptotic alpha beta T cells was confirmed by electron microscopy. About half of all the apoptotic cells within the spinal cord were labelled by these antibodies. It is possible that some of the unlabelled apoptotic cells were also T lymphocytes but that others were glial cells such as oligodendrocytes. One possible interpretation of this T-cell apoptosis is that it represents activation-induced cell death, which has recently been shown to provide a mechanism of clonal elimination of mature as well as immature autoreactive T cells. Another possible interpretation is that it is a result of corticosterone released during the course of EAE. The apoptotic elimination of target-antigen-specific lymphocytes within the target organ in this autoimmune disease may contribute to the subsidence of inflammation and, if ongoing, to the development of tolerance.

Animals↗
PubMed1992

Neuropathological findings in chronic relapsing experimental allergic neuritis induced in the Lewis rat by inoculation with intradural root myelin and treatment with low dose cyclosporin A.

Experimental allergic neuritis (EAN) was induced in Lewis rats by inoculation with bovine intradural root myelin and adjuvants. Rats treated with subcutaneous cyclosporin A (CsA) (4 mg/kg on 3 days per week from the day of inoculation until day 29) developed a chronic relapsing course. Tissues from the spinal cord, nerve roots, dorsal root ganglia and sciatic nerve of CsA-treated rats sampled during relapses and remissions were studied by light and electron microscopy. Control rats that were not treated with CsA were studied during or after episodes of acute EAN. Both control and CsA-treated animals studied in the first episode of EAN had evidence of inflammation and primary demyelination of the nerve roots and dorsal root ganglia. In control and CsA-treated animals that had recovered from the first episode there was evidence of remyelination. In CsA-treated animals in the second episode there was severe inflammation and demyelination and remyelination of the nerve roots and dorsal root ganglia, and in addition there was significant demyelination and remyelination in the spinal nerves and sciatic nerves and dorsal columns of the spinal cord, particularly in later stages of disease. In later episodes there was less inflammation, but there was continuing demyelination and onion bulbs were present. In animals sampled after recovery from chronic relapsing EAN onion bulbs were present. Occasional small onion bulbs were also observed in control animals that were inoculated with higher doses of myelin. Plasma cells were present in the inflammatory lesions of later episodes. Mast cells were also observed at different stages of the disease. We conclude that the CsA form of chronic relapsing EAN has clinical and pathological similarities with the human disease, chronic inflammatory demyelinating polyradiculoneuropathy.

Anesthesia↗
PubMed1992

Spasticity and white matter abnormalities in adult phenylketonuria.

A 19 year old male with phenylketonuria (PKU) developed a spastic paparesis 8 months after stopping his restricted phenylalanine diet. CT and MRI showed abnormalities of the deep cerebral white matter, and visual evoked response latencies were prolonged. The spasticity gradually improved over several months after resuming the PKU diet. A repeat MRI scan was unchanged. His brother also had PKU and ceased dietary restrictions, but his only neurological abnormality was a slight increase in the deep tendon reflexes of the lower limbs. CT and MRI of his brain was normal. DNA analysis showed that both brothers were homozygous for the same PKU mutation. These patients demonstrate that reversible neurological signs may develop in patients with classic PKU after ceasing dietary restrictions and that these may be associated with abnormalities seen on neuro-imaging.

Adult↗