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Critical points of tumor necrosis factor action in central nervous system autoimmune inflammation defined by gene targeting.

Körner H, Riminton DS, Strickland DH, Lemckert FA, Pollard JD, Sedgwick JD - J. Exp. Med. (1997)

Bottom Line: In this way a single gene effect was studied.These results are consistent with the TNF dependence of processes controlling initial leukocyte movement within the CNS.Nevertheless, potent alternative mechanisms exist to mediate all other phases of EAE.

View Article: PubMed Central - PubMed

Affiliation: Centenary Institute of Cancer Medicine and Cell Biology, Royal Prince Alfred Hospital, Sydney, New South Wales, 2050 Australia.

ABSTRACT
Tumor necrosis factor (TNF)-dependent sites of action in the generation of autoimmune inflammation have been defined by targeted disruption of TNF in the C57BL/6 mouse strain. C57BL/6 mice are susceptible to an inflammatory, demyelinating form of experimental autoimmune encephalomyelitis (EAE) induced by the 35-55 peptide of myelin oligodendrocyte glycoprotein. Direct targeting of a strain in which EAE was inducible was necessary, as the location of the TNF gene renders segregation of the mutated allele from the original major histocompatibility complex by backcrossing virtually impossible. In this way a single gene effect was studied. We show here that TNF is obligatory for normal initiation of the neurological deficit, as demonstrated by a significant (6 d) delay in disease in its absence relative to wild-type (WT) mice. During this delay, comparable numbers of leukocytes were isolated from the perfused central nervous system (CNS) of WT and TNF-/- mice. However, in the TNF-/- mice, immunohistological analysis of CNS tissue indicated that leukocytes failed to form the typical mature perivascular cuffs observed in WT mice at this same time point. Severe EAE, including paralysis and widespread CNS perivascular inflammation, eventually developed without TNF. TNF-/- and WT mice recovered from the acute illness at the same time, such that the overall disease course in TNF-/- mice was only 60% of the course in control mice. Primary demyelination occurred in both WT and TNF-/- mice, although it was of variable magnitude. These results are consistent with the TNF dependence of processes controlling initial leukocyte movement within the CNS. Nevertheless, potent alternative mechanisms exist to mediate all other phases of EAE.

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Peak disease inflammation and demyelination. (A)  Leukocyte infiltration and formation of perivascular cuffs. Sections  were derived from spinal cord of  animals harvested at day 19 (WT)  and day 23 (TNF−/−) and stained  for CD45. CD45+ filamentous  processes within the CNS parenchyma (arrows) indicate activated  microglia. Comparable infiltration was found at all levels of the  spinal cord, brain stem, and cerebellum. Bar = 60 μm. (B) Primary demyelination in WT and  TNF−/− mice. Sections were derived from spinal cord of mice  harvested at day 35 (WT) and  day 40 (TNF−/−). Tissues from  WT and TNF−/− mice show a  region of comparable perivenous  (v) demyelination and gliosis beneath the meningeal surface (m).  Arrows indicate naked (demyelinated) axons. In these mice, a  similar histological picture was  obtained at all levels of the spinal  cord. Bar = 12 μm.
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Figure 3: Peak disease inflammation and demyelination. (A) Leukocyte infiltration and formation of perivascular cuffs. Sections were derived from spinal cord of animals harvested at day 19 (WT) and day 23 (TNF−/−) and stained for CD45. CD45+ filamentous processes within the CNS parenchyma (arrows) indicate activated microglia. Comparable infiltration was found at all levels of the spinal cord, brain stem, and cerebellum. Bar = 60 μm. (B) Primary demyelination in WT and TNF−/− mice. Sections were derived from spinal cord of mice harvested at day 35 (WT) and day 40 (TNF−/−). Tissues from WT and TNF−/− mice show a region of comparable perivenous (v) demyelination and gliosis beneath the meningeal surface (m). Arrows indicate naked (demyelinated) axons. In these mice, a similar histological picture was obtained at all levels of the spinal cord. Bar = 12 μm.

Mentions: At the peak of the disease there was extensive inflammation in the CNS of both WT and TNF−/− mice (Fig. 3 A), characterized by perivascular and submeningeal infiltrates of CD45+ cells and microglial activation (Fig. 3 A, arrows). Serial section staining revealed a predominance of macrophages and CD4+ T cells (data not shown). A general feature of the immunopathology in TNF−/− mice was a more limited expansion of cells from the perivascular cuff into the parenchyma. Primary demyelination, involving loss of myelin from otherwise viable axons, is a hallmark of the human disease multiple sclerosis, for which EAE serves as an experimental model (2). Primary demyelination was a relatively late event, detected in WT and TNF−/− mice from ∼30 d after MOG peptide/CFA immunization and most clearly apparent after the bulk of inflammatory cells had dissipated (Fig. 3 B, day 35). Naked axons of otherwise normal appearance were seen, consistent with the specificity of the immune insult (Fig. 3 B, arrows). A degree of variability in magnitude of demyelination was observed in TNF−/− mice with from one of five mice examined exhibiting few if any demyelinated axons (data not shown), to the one mouse illustrated here (Fig. 3 B, day 40) with a level of demyelination indistinguishable from WT mice. A more extensive comparison of WT and TNF−/− mice is currently underway to determine whether the levels of demyelination in mice lacking TNF are reduced overall. Nevertheless, TNF is not an obligatory mediator in the demyelinating process.


Critical points of tumor necrosis factor action in central nervous system autoimmune inflammation defined by gene targeting.

Körner H, Riminton DS, Strickland DH, Lemckert FA, Pollard JD, Sedgwick JD - J. Exp. Med. (1997)

Peak disease inflammation and demyelination. (A)  Leukocyte infiltration and formation of perivascular cuffs. Sections  were derived from spinal cord of  animals harvested at day 19 (WT)  and day 23 (TNF−/−) and stained  for CD45. CD45+ filamentous  processes within the CNS parenchyma (arrows) indicate activated  microglia. Comparable infiltration was found at all levels of the  spinal cord, brain stem, and cerebellum. Bar = 60 μm. (B) Primary demyelination in WT and  TNF−/− mice. Sections were derived from spinal cord of mice  harvested at day 35 (WT) and  day 40 (TNF−/−). Tissues from  WT and TNF−/− mice show a  region of comparable perivenous  (v) demyelination and gliosis beneath the meningeal surface (m).  Arrows indicate naked (demyelinated) axons. In these mice, a  similar histological picture was  obtained at all levels of the spinal  cord. Bar = 12 μm.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2199118&req=5

Figure 3: Peak disease inflammation and demyelination. (A) Leukocyte infiltration and formation of perivascular cuffs. Sections were derived from spinal cord of animals harvested at day 19 (WT) and day 23 (TNF−/−) and stained for CD45. CD45+ filamentous processes within the CNS parenchyma (arrows) indicate activated microglia. Comparable infiltration was found at all levels of the spinal cord, brain stem, and cerebellum. Bar = 60 μm. (B) Primary demyelination in WT and TNF−/− mice. Sections were derived from spinal cord of mice harvested at day 35 (WT) and day 40 (TNF−/−). Tissues from WT and TNF−/− mice show a region of comparable perivenous (v) demyelination and gliosis beneath the meningeal surface (m). Arrows indicate naked (demyelinated) axons. In these mice, a similar histological picture was obtained at all levels of the spinal cord. Bar = 12 μm.
Mentions: At the peak of the disease there was extensive inflammation in the CNS of both WT and TNF−/− mice (Fig. 3 A), characterized by perivascular and submeningeal infiltrates of CD45+ cells and microglial activation (Fig. 3 A, arrows). Serial section staining revealed a predominance of macrophages and CD4+ T cells (data not shown). A general feature of the immunopathology in TNF−/− mice was a more limited expansion of cells from the perivascular cuff into the parenchyma. Primary demyelination, involving loss of myelin from otherwise viable axons, is a hallmark of the human disease multiple sclerosis, for which EAE serves as an experimental model (2). Primary demyelination was a relatively late event, detected in WT and TNF−/− mice from ∼30 d after MOG peptide/CFA immunization and most clearly apparent after the bulk of inflammatory cells had dissipated (Fig. 3 B, day 35). Naked axons of otherwise normal appearance were seen, consistent with the specificity of the immune insult (Fig. 3 B, arrows). A degree of variability in magnitude of demyelination was observed in TNF−/− mice with from one of five mice examined exhibiting few if any demyelinated axons (data not shown), to the one mouse illustrated here (Fig. 3 B, day 40) with a level of demyelination indistinguishable from WT mice. A more extensive comparison of WT and TNF−/− mice is currently underway to determine whether the levels of demyelination in mice lacking TNF are reduced overall. Nevertheless, TNF is not an obligatory mediator in the demyelinating process.

Bottom Line: In this way a single gene effect was studied.These results are consistent with the TNF dependence of processes controlling initial leukocyte movement within the CNS.Nevertheless, potent alternative mechanisms exist to mediate all other phases of EAE.

View Article: PubMed Central - PubMed

Affiliation: Centenary Institute of Cancer Medicine and Cell Biology, Royal Prince Alfred Hospital, Sydney, New South Wales, 2050 Australia.

ABSTRACT
Tumor necrosis factor (TNF)-dependent sites of action in the generation of autoimmune inflammation have been defined by targeted disruption of TNF in the C57BL/6 mouse strain. C57BL/6 mice are susceptible to an inflammatory, demyelinating form of experimental autoimmune encephalomyelitis (EAE) induced by the 35-55 peptide of myelin oligodendrocyte glycoprotein. Direct targeting of a strain in which EAE was inducible was necessary, as the location of the TNF gene renders segregation of the mutated allele from the original major histocompatibility complex by backcrossing virtually impossible. In this way a single gene effect was studied. We show here that TNF is obligatory for normal initiation of the neurological deficit, as demonstrated by a significant (6 d) delay in disease in its absence relative to wild-type (WT) mice. During this delay, comparable numbers of leukocytes were isolated from the perfused central nervous system (CNS) of WT and TNF-/- mice. However, in the TNF-/- mice, immunohistological analysis of CNS tissue indicated that leukocytes failed to form the typical mature perivascular cuffs observed in WT mice at this same time point. Severe EAE, including paralysis and widespread CNS perivascular inflammation, eventually developed without TNF. TNF-/- and WT mice recovered from the acute illness at the same time, such that the overall disease course in TNF-/- mice was only 60% of the course in control mice. Primary demyelination occurred in both WT and TNF-/- mice, although it was of variable magnitude. These results are consistent with the TNF dependence of processes controlling initial leukocyte movement within the CNS. Nevertheless, potent alternative mechanisms exist to mediate all other phases of EAE.

Show MeSH
Related in: MedlinePlus