| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Short Communications |

From the Department of Neuroimmunology,*
Max-Planck-Institute of Neurobiology, Martinsried, Germany; and the
Department of Pathology,
Experimental
Immunology, University of Zurich, Zurich, Switzerland
| Abstract |
|---|
|
|
|---|
and tetrodotoxin to express major histocompatibility complex class I
were pulsed with a dominant peptide of the lymphochoriomeningitis virus
envelope glycoprotein (GP33) and then confronted with GP33-specific
CD8+ CTLs. Within 3 hours the neurites developed
cytoskeleton breaks with adjacent solitary neuritic spheroids,
as documented by confocal examination of the cytoskeletal marker
ß-tubulin III. At the same time cytoskeleton staining of the neuronal
somata showed no damage. The CTLs selectively attacked neurites and
induced segmental membrane disruption 5 to 30 minutes after the
establishment of peptide-specific CTL-neurite contact, as
directly visualized by live confocal imaging. Thus, major
histocompatibility complex class I/peptide-restricted CD8+
T lymphocytes can induce lesions to neurites, which might be
responsible for axonal damage during neuroinflammatory
diseases.
| Introduction |
|---|
|
|
|---|
(IFN-
)
when concomitantly the neuronal activity was blocked with tetrodotoxin
(TTX).4,5
MHC class I expression should render neurons
susceptible to cytotoxic T lymphocyte attack. However, we found that
neuronal cell bodies, although expressing MHC class I, are protected
against early peptide-specific or alloreactive cytotoxic T lymphocyte
(CTL)- mediated lysis6
and might be killed later solely
via Fas/CD95 mediated apoptosis. Neurons are highly polarized cells7 and in most studies little attention has been paid to the conditions of the axons or dendrites following T lymphocyte cytotoxicity.8-10 Interestingly, while neuronal cell bodies seem to be relatively protected against overt cytotoxicity in most neuroinflammatory processes,11 their neurites are often damaged during viral infections12-15 or central nervous system (CNS) autoimmune diseases.16,17 For example, axonal injury is a common neuropathological feature in the Theilers murine encephalomyelitis virus model.12 In this model the axonal damage was more closely related to the severity of clinical disease than the degree of demyelination.12 Further, axonal damage and neurological deficits were absent in ß2-microgobulin-deficient mice lacking functional MHC class I molecules despite extensive demyelination.12 Damage to neurites with transection of axons and formation of neurite spheroids were also observed in demyelinated, inflammatory multiple sclerosis (MS) lesions.16,17 In MS, neurite damage was associated with the number of CD8+ T lymphocytes infiltrating the lesion.18 Again, damage of neurites appears to be responsible for the persistent neurological deficits seen in these patients.19 Thus, in both viral and autoimmune CNS disease, neurites are selectively and locally damaged during the inflammatory process by a mechanism which still has to be elucidated.
In this study we analyzed the interaction between cytotoxic T lymphocytes and neurites in vitro. By performing live imaging we directly visualized the CTL-neurite interaction and showed that antigen-specific CTLs are directly capable of damaging neurites in a MHC class I/peptide-restricted fashion.
| Materials and Methods |
|---|
|
|
|---|
Hippocampal cell cultures were prepared from embryonic day 16 mice
(C57BL/6; Max-Planck-Institute of Neurobiology and Biochemistry,
Martinsried, Germany) as previously described.4
Dissociated neurons were cultured in Basal Medium Eagle (BME, Gibco,
BRL) with the B27 supplements (Gibco, BRL), glucose (1%
(v/v), Sigma), and fetal calf serum (FCS; 1% w/v; Pan System,
Würzburg, Germany). Recombinant mouse IFN-
(100
U/ml; Laboserv, Giessen, Germany) and TTX (1 µmol/L, Sigma) were
added to the cultures for 72 hours as indicated.
MHC Class I Immunohistochemistry
Hippocampal neuronal cultures were fixed in 4% paraformaldehyde and incubated with rat monoclonal antibody directed against mouse MHC class I (1:100, ER-HR52; Dianova, Hamburg, Germany) followed by secondary fluorochrome Cy3-conjugated goat antibody directed against rat immunoglobulin (IgG) (10 µg/ml; Dianova). Cells were then washed and incubated with mouse monoclonal antibody specific for MAP2 (10 µg/ml; Sigma) and secondary dichlorotriaziny-aminofluorescein (DTAF)-conjugated goat antibody directed against mouse IgG (10 µg/ml; Dianova). For triple labeling, cultures were then incubated with a mouse monoclonal antibody directed against ß-tubulin III (2 µg/ml; Sigma) and Cy5-conjugated goat antibody directed against mouse IgG (10 µg/ml; Dianova). Optical sections along the z-axis were scanned with a confocal laser-scanning microscope (63x oil objective, Leica, Inc., Deerfield, IL). Baseline labeling for MHC class I was revealed with primary purified rat immunoglobulin (10 µg/ml; Dianova) and secondary fluorochrome-conjugated goat antibodies to rat IgG.
Generation of GP33-Specific Cytotoxic T Lymphocytes and Peptide Loading of Target Cells
Spleen cell suspensions were obtained from lymphochoriomeningitis
virus (LCMV) infected C57Bl/6 mice (200 plaque forming units LCMV-WE at
least 3 months previously) and cultured in Iscoves modified
Dulbeccos medium (Gibco, BRL) supplemented with 10% FCS (Pan
System), penicillin-streptomycin, 2-mercaptoethanol, 0.1 ng/ml
mIL-7 (Biosource Int., Camarillo, CA) and 10% IL-2 containing
supernatant. Cultures were restimulated at 10-day intervals with
irradiated RMA-S cells pulsed with peptide GP33 (10 ng/ml, peptide
GP3341, KAVYNFATC, Neosystem S.A., Strasbourg, France). CTL lines
were used for experimentation after three rounds of restimulation, a
time at which the CTLs exhibited a CD8+,
ß T
cell receptor phenotype and were highly specific for the LCMV GP33
peptide, but not LCMV peptide GP276 or NP396, as determined by
cytotoxicity assays.20
CTL cultures were recovered from a
gradient at day 7 after stimulation and then used for killing assays.
Target cells were pulsed with 1 x 10-7
mol/L of the H-2Db-restricted LCMV peptide GP33
or the H-2Db-restricted influenza virus
nucleocapsid peptide NP 366374 (ASNENMETM, Neosystem S.A.).
Cytoskeleton Immunohistochemistry
Hippocampal neuronal cultures were fixed in 4% paraformaldehyde at 3 hours after addition of CTLs and then were incubated with the mouse monoclonal antibody specific for ß-tubulin III (10 µg/ml; Sigma) and secondary fluorochrome DTAF-conjugated goat antibody directed against mouse IgG (10 µg/ml; Dianova). Optical sections along the z-axis were scanned with a confocal laser-scanning microscope (63x oil objective, Leica, Inc.). Frequency of localized lesion sites with adjacent solitary neurite cytoskeleton spheroids were determined from at least three independent experiments. Degenerated neurons with "beaded" neurites sporadically detectable in neuronal cell cultures were excluded from the analysis.
Confocal Imaging of Plasma Membranes
During confocal microscopy, cells were maintained at 37°C in
imaging buffer consisting of 142 mmol/L NaCl, 5.4 mmol/L KCl, 1.8
mmol/L CaCl2, 0.8 mmol/L
MgSO4, 1 mmol/L
NaH2PO4, 5 mmol/L glucose,
25 mmol/L Hepes, 0.1% bovine serum albumin, 1% (v/v) FCS, and 1
µmol/L TTX, adjusted to pH 7.4. CTLs were added to the neuronal
cultures at an effector/target ratio adjusted to 5:1. The fluorescence
plasma membrane dye FM143 (15 µmol/L, Molecular Probes) was applied
to the cells and images were obtained with the confocal laser scanning
microscope (40x oil objective, Leica, Inc.). Laser intensity was
reduced to a minimum to avoid phototoxicity. Optical sections of
selected areas were obtained along the z-axis every 5 minutes.
Percentage of transected neurites at the contact site of CTLs within 1
hour of GP33- or influenza virus peptide-pulsed and pretreated (IFN-
plus TTX) neurons was determined from at least three independent
experiments.
| Results |
|---|
|
|
|---|
In culture, neurons derived from hippocampi of C57BL/6 mice did
not show constitutive expression of MHC class I on their plasma
membrane. However, expression of MHC class I molecules on the cell
membrane is inducible on most neurons via treatment with IFN-
and is
increased by concomitant blockade of neuronal activity with
TTX.6
The MHC class I surface expression induced by
72-hour treatment with IFN-
and TTX was not restricted
to the neuronal somata, but also detected on neurites (Figure 1)
. Triple labeling with antibodies
against MHC class I, ß-tubulin III and microtubule-associated
protein-2 (MAP2) detected MHC class I molecules both on dendrites
stained for the dendritic cytoskeleton protein MAP2 and on axons
positive for the neuronal cytoskeleton protein ß-tubulin III, but
not the dendritic marker protein MAP2 (Figure 1)
. After having
confirmed inducibility of MHC class I on axons and dendrites we
investigated whether T lymphocytes have the potential to induce neurite
damage like that observed in viral and autoimmune inflammatory CNS
disease.
|
To analyze the interaction between cytotoxic T lymphocytes and
neurites we propagated CTLs specific for the dominant peptide of LCMV
envelope glycoprotein (GP33). These CTLs have a CD8,
ßTCR
phenotype and are highly specific for LCMV peptide GP33,6
presented in context of H-2Db. When neurons were
pulsed with peptide GP33 the CTLs rapidly attached to neuronal cell
bodies and neurites. To study structural changes in the neurites
following CTL attack, we fixed the cultures 3 hours after CTL attack
and performed immunocytochemistry for ß-tubulin III. At this time
neuronal cell bodies did not show any cytoskeleton pathology. In
striking contrast, the neurite cytoskeleton was selectively disrupted
at distinct sites (Figure 2A)
. The
neurites showed segmental cytoskeleton damage over a length of 3 to 6
µm. Adjacent to the local lesions, cytoskeleton spheroids of 2 to 3
µm in diameter developed, demonstrating accumulation of cytoskeleton
proteins (Figure 2, B and C)
. In most cases the ß-tubulin III
labeling was completely lost at the lesioned site, indicating
disruption of the cytoskeleton and transection of the neurite. The
number of single cytoskeletal spheroids adjacent to segmental neurite
disruption was determined following CTL attack. On average, localized
neurite lesion sites with adjacent solitary neurite cytoskeleton
spheroids were detected at a frequency of 0.85/neuron in cell cultures
expressing MHC class I and pulsed with peptide GP33 at 3 hours after
CTL attack (Figure 2D)
. These localized cytoskeleton changes were not
detectable in neurons lacking MHC class I expression, or neurons pulsed
with the influenza virus control peptide (Figure 2D)
.
|
To confirm that CTLs can directly cause local transection of
neurites, live interactions between CTLs and neurites were sequentially
recorded using confocal laser scanning microscopy over a 60-minute time
period. Neurons were pretreated with IFN-
(100 U/ml) and TTX (1
µmol/L) to induce MHC class I expression and plasma membranes were
visualized with the fluorescent dye, FM143. Approximately 2 to 5
minutes after contact of the CTLs with neurites presenting peptide
GP33, structural alterations were observed in neurite membranes (Figure 3A)
. First, the neurites showed irregular
labeling with the fluorescence dye at the point of contact, indicating
beginning discontinuity of the membrane. Within 10 to 30 minutes of
contact with the CTL, transection of neurites was detected by complete
disruption of the plasma membrane (Figure 3A)
. Transection of neurites
was directly observed at the region of contact with the CTL. The CTLs
then either detached or remained adhered to one of the neuritic ends.
The separated neuritic ends showed increased membrane dye uptake and
appeared to reseal. Localized membrane damage of neurites at the point
of CTL contact was dependent on the presentation of the LCMV peptide
GP33. In detail, 16 of 34 (47.1% ± 16.6% SEM) individual CTL-neurite
interactions observed in five independent experiments using confocal
microscopy over a 60-minute period resulted in localized transection of
neurites as visualized by disruption of the membrane fluorescence dye
(Figure 3B)
. Membrane damage with transection of neurites was
detectable, on average, 25.3 minutes (±14.9 SD) after establishment of
CTL-neurite contacts. In contrast, the majority of CTLs did not form
stable conjugates with neurites of cultures pulsed with the control
peptide. Most CTLs detached from established CTL-neurite contacts
within 5 to 10 minutes. Only 5 of 51 (9.8% ± 2.6% SEM) of
CTL-neurite interactions caused minor membrane changes in the presence
of the control influenza virus peptide (Figure 3B)
.
|
| Discussion |
|---|
|
|
|---|
Neurite damage could be caused either directly by a local injury or secondary to neuronal cell death. In the present study we monitored live interactions between CTLs and neurites by continuous imaging, thus allowing localization of membrane lesions opposite to the CTL-neuronal contacts. No sign of neurite damage was observed in non-stimulated, non-MHC expressing neurons following attack by CTLs. Neurite damage depended on the induction of appropriate MHC class I molecules on the neuronal membrane, and on the presence of specific antigenic peptides. This observation and the rapid development of membrane lesions within 0.5 hour are consistent with a perforin mediated lysis pathway exerted by CD8+ CTLs.
Interestingly, about 50% of the stable CTL-neurite conjugates showed
complete transection of the membrane. Further, no repair of the
transected neurite was observed during our live imaging experiments.
Thus, it must be hypothesized that a round of "hits" from a single
CTL interaction is sufficient to induce irreversible damage to a
neurite. In principle, damage to neurites might be triggered by soluble
mediators rapidly released in response to recognition of MHC/peptide by
CTLs. However, such characteristic localized damage of neuritis with
spheroid formation has not been observed after tumor necrosis
factor-
or IFN-
treatment (unpublished observation). Further,
damage to neurites was not observed in identical neuronal cultures
challenged with autoreactive CD4+ T cells
(unpublished observations).
This early cytotoxicity of T lymphocytes was restricted to neurites and was undetectable at the neuronal cell bodies, confirming our previous observation that neuronal cell bodies are protected against CTL mediated lysis.6 Further, we did not observe neurite damage in close proximity to the neuronal cell bodies. Distinct susceptibility to rapid CTL-mediated lysis between neuronal soma and neurites might be explained by regional differences of neuronal membranes and underlying cytoplasm. After neuronal polarization, axonal membranes and cytoskeleton become distinct from the rest of the cell.7 In particular, membrane receptors and their molecular links to the cytoskeleton22 may differ in a way that influence neurite/soma susceptibility to CTL-mediated cytoskeleton disruption, as revealed in our experiments. One obvious candidate would be MHC class I. However, expression of MHC class I was not found to be expressed differentially in the cell soma and neurites.
The finding that neurites are selectively damaged, while the cell soma is protected against CTL lysis, was somehow unexpected but might have emerged during evolution to limit the spread of viral and microbial organisms. It has been shown that microbes are transported along axons and dendrites as well as trans-synaptically, which can lead to fast and fulminant spread of infections.23 Transection of infected neurites would efficiently limit transport and spread of microbes, while intact neuronal soma could survive to minimize loss of neurons, which have a very low regenerative capacity.
Our data that CTLs can transect neurites may have implications for understanding neuroinflammatory diseases. While neuronal cell bodies seem to be relatively protected against overt cytotoxicity in most neuroinflammatory processes, their neurites are often damaged during viral infections or CNS autoimmune diseases. For example, this pattern of axonal injury is observed in the Theilers murine encephalomyelitis virus model.12 In this model, the axonal damage was also dependent on MHC class I expression and more closely related to the severity of clinical disease than the degree of demyelination.
In MS, a demyelinating inflammatory disease with putative autoimmune pathogenesis, axonal disruption is a prominent feature of the plaque.16,17 Formation of axonal spheroids and bulbs, as they reflect axonal dissection in the MS lesion, are caused by accumulation of cytoskeleton proteins, either resulting from retracted neurites or interrupted cytoskeletal transport. Very similar segmental cytoskeleton changes of neurites (spheroid and bulb formations) were detected in our culture system after 3 hours, while membrane disruption was already obvious after 0.5 hour after specific CTL attack.
This raises the possibility that autoimmune CTL-mediated mechanisms may contribute to axonal damage commonly seen in MS plaques.17 According to current dogma, MS is initiated and controlled by an autoimmune reaction against brain white matter.24 This immune attack induces focal demyelinated areas, which might enable CTLs to get in contact with neurites. It was assumed that these brain autoimmune T cells assault myelin presenting cells, but spare neurons, which express neither MHC products nor myelin autoantigen. More recent work revealed, however, that neurons are indeed inducible to produce MHC class I molecules, especially in a functionally compromised state.4,5 Furthermore, several myelin proteins have been demonstrated in neurons. They include proteolipid protein25 as well as golli-myelin basic protein.26 Thus, in demyelinated, inflammatory brain lesions, the structural prerequisites for CTL27 attack against MHC class I-induced axons, are given. It is tempting to speculate that the CD8+-enriched immune infiltrates co-localizing with axonal damage, as recently described in certain MS lesions, indeed involve CTL- mediated immune attacks.28
In conclusion, involvement of cytotoxic CD8+ T lymphocytes in damage of neurites during neuroinflammatory diseases should be considered as a possible pathogenic mechanism having important consequences for therapeutic immune intervention.
| Acknowledgements |
|---|
| Footnotes |
|---|
Supported by DFG (SFB 391) and by the Volkswagen-Foundation.
Accepted for publication May 25, 2001.
| References |
|---|
|
|
|---|
and tumor necrosis factor-
. J Exp Med 1997, 185:305-316This article has been cited by other articles:
![]() |
R. Dutta and B. D. Trapp Pathogenesis of axonal and neuronal damage in multiple sclerosis Neurology, May 29, 2007; 68(22_suppl_3): S22 - S31. [Abstract] [Full Text] [PDF] |
||||
![]() |
I. Metz, C. F. Lucchinetti, H. Openshaw, A. Garcia-Merino, H. Lassmann, M. S. Freedman, H. L. Atkins, B. Azzarelli, O. J. Kolar, and W. Bruck Autologous haematopoietic stem cell transplantation fails to stop demyelination and neurodegeneration in multiple sclerosis Brain, May 1, 2007; 130(5): 1254 - 1262. [Abstract] [Full Text] [PDF] |
||||
![]() |
C. Wegner, M. M. Esiri, S. A. Chance, J. Palace, and P. M. Matthews Neocortical neuronal, synaptic, and glial loss in multiple sclerosis. Neurology, September 26, 2006; 67(6): 960 - 967. [Abstract] [Full Text] [PDF] |
||||
![]() |
L. P. Shriver and B. N. Dittel T-Cell-Mediated Disruption of the Neuronal Microtubule Network: Correlation with Early Reversible Axonal Dysfunction in Acute Experimental Autoimmune Encephalomyelitis Am. J. Pathol., September 1, 2006; 169(3): 999 - 1011. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. Brisebois, S. P. Zehntner, J. Estrada, T. Owens, and S. Fournier A Pathogenic Role for CD8+ T Cells in a Spontaneous Model of Demyelinating Disease J. Immunol., August 15, 2006; 177(4): 2403 - 2411. [Abstract] [Full Text] [PDF] |
||||
![]() |
C. W. Ip, A. Kroner, M. Bendszus, C. Leder, I. Kobsar, S. Fischer, H. Wiendl, K.-A. Nave, and R. Martini Immune Cells Contribute to Myelin Degeneration and Axonopathic Changes in Mice Overexpressing Proteolipid Protein in Oligodendrocytes J. Neurosci., August 2, 2006; 26(31): 8206 - 8216. [Abstract] [Full Text] [PDF] |
||||
![]() |
R. Gold, C. Linington, and H. Lassmann Understanding pathogenesis and therapy of multiple sclerosis via animal models: 70 years of merits and culprits in experimental autoimmune encephalomyelitis research Brain, August 1, 2006; 129(8): 1953 - 1971. [Abstract] [Full Text] [PDF] |
||||
![]() |
T. Wang, R. Allie, K. Conant, N. Haughey, J. Turchan-Chelowo, K. Hahn, A. Rosen, J. Steiner, S. Keswani, M. Jones, et al. Granzyme B mediates neurotoxicity through a G-protein-coupled receptor FASEB J, June 1, 2006; 20(8): 1209 - 1211. [Abstract] [Full Text] [PDF] |
||||
![]() |
Y. Zhu, J. Antony, S. Liu, J. A. Martinez, F. Giuliani, D. Zochodne, and C. Power CD8+ lymphocyte-mediated injury of dorsal root ganglion neurons during lentivirus infection: CD154-dependent cell contact neurotoxicity. J. Neurosci., March 29, 2006; 26(13): 3396 - 3403. [Abstract] [Full Text] [PDF] |
||||
![]() |
E Fainardi, R Rizzo, L Melchiorri, M Castellazzi, E Paolino, M R Tola, E Granieri, and O R Baricordi Intrathecal synthesis of soluble HLA-G and HLA-I molecules are reciprocally associated to clinical and MRI activity in patients with multiple sclerosis Multiple Sclerosis, February 1, 2006; 12(1): 2 - 12. [Abstract] [PDF] |
||||
![]() |
I. Tsunoda, L.-Q. Kuang, M. Kobayashi-Warren, and R. S. Fujinami Central Nervous System Pathology Caused by Autoreactive CD8+ T-Cell Clones following Virus Infection J. Virol., December 1, 2005; 79(23): 14640 - 14646. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. A. Friese and L. Fugger Autoreactive CD8+ T cells in multiple sclerosis: a new target for therapy? Brain, August 1, 2005; 128(8): 1747 - 1763. [Abstract] [Full Text] [PDF] |
||||
![]() |
D.-A. Laplaud, C. Ruiz, S. Wiertlewski, S. Brouard, L. Berthelot, M. Guillet, B. Melchior, N. Degauque, G. Edan, P. Brachet, et al. Blood T-cell receptor {beta} chain transcriptome in multiple sclerosis. Characterization of the T cells with altered CDR3 length distribution Brain, May 1, 2004; 127(5): 981 - 995. [Abstract] [Full Text] [PDF] |
||||
![]() |
T. B. Jones, D. P. Ankeny, Z. Guan, V. McGaughy, L. C. Fisher, D. M. Basso, and P. G. Popovich Passive or Active Immunization with Myelin Basic Protein Impairs Neurological Function and Exacerbates Neuropathology after Spinal Cord Injury in Rats J. Neurosci., April 14, 2004; 24(15): 3752 - 3761. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. Rodriguez, L. J. Zoecklein, C. L. Howe, K. D. Pavelko, J. D. Gamez, S. Nakane, and L. M. Papke Gamma Interferon Is Critical for Neuronal Viral Clearance and Protection in a Susceptible Mouse Strain following Early Intracranial Theiler's Murine Encephalomyelitis Virus Infection J. Virol., November 15, 2003; 77(22): 12252 - 12265. [Abstract] [Full Text] [PDF] |
||||
![]() |
M Bradl and R Hohlfeld Molecular pathogenesis of neuroinflammation J. Neurol. Neurosurg. Psychiatry, October 1, 2003; 74(10): 1364 - 1370. [Abstract] [Full Text] [PDF] |
||||
![]() |
F. Giuliani, C. G. Goodyer, J. P. Antel, and V. W. Yong Vulnerability of Human Neurons to T Cell-Mediated Cytotoxicity J. Immunol., July 1, 2003; 171(1): 368 - 379. [Abstract] [Full Text] [PDF] |
||||
![]() |
H Lassmann Axonal injury in multiple sclerosis J. Neurol. Neurosurg. Psychiatry, June 1, 2003; 74(6): 695 - 697. [Full Text] [PDF] |
||||
![]() |
M. Rodriguez A function of myelin is to protect axons from subsequent injury: implications for deficits in multiple sclerosis Brain, April 1, 2003; 126(4): 751 - 752. [Full Text] [PDF] |
||||
![]() |
I. M. Medana and M. M. Esiri Axonal damage: a key predictor of outcome in human CNS diseases Brain, March 1, 2003; 126(3): 515 - 530. [Abstract] [Full Text] [PDF] |
||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |