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Department of Neuropathology, Tokyo Metropolitan Institute for Neuroscience, Tokyo, Japan
| Abstract |
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| Introduction |
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We have recently applied CDR3 spectratyping for the analysis of oligoclonality of TCR of T cells which are responsible for the development of experimental autoimmune encephalomyelitis (EAE), an animal model for MS (6). In rat acute EAE, several groups including us reported that T cells bearing Vß8.2 TCR, which is frequently used by in vitro-established encephalitogenic T cell clones (7, 8), appear in the CNS parenchyma, especially at the early stage of the disease, and that a large number of these Vß8.2 TCR clones possess a common motif in their CDR3 region (9, 10, 11, 12). Based on these findings, we recently screened 22 spectratypes (Vß120) derived from T cells isolated from spinal cord lesions by CDR3 spectratyping and found that Vß8.2 spectratype with the shortest CDR3 is clonally expanded throughout the course of acute EAE (6). Furthermore, the EAE-specific nucleotide sequence is highly preserved in the CDR3 region. These results indicate that CDR3 spectratyping and subsequent sequencing of the CDR3 region of spectratype-derived TCR clones can be applicable for the detailed analysis of TCR of MS patients, the character of which is much more complicated than that of animal models as mentioned above.
In the present study, we performed CDR3 spectratyping analysis using spinal cord T cells and PBL isolated from rats with chronic relapsing EAE. Special attention was paid to the following points. First, is the EAE-specific spectratype pattern recognized in acute MBP-induced EAE also found in chronic relapsing EAE induced with spinal cord homogenate? Second, do changes in EAE-specific spectratype pattern occur in the course of chronic relapsing EAE? Consequently, it was found that EAE-specific spectratype pattern seen in acute EAE was also detectable in chronic relapsing EAE throughout the disease, suggesting that an encephalitogen in spinal cord homogenate is the same as that used for acute EAE induction. Thus, the determination of CDR3 size by spectratyping has been shown to be a powerful tool with which to analyze the T cell repertoire of T cell-mediated autoimmune diseases. Analysis of MS patients by CDR3 spectratyping may provide useful information about the nature of MS-associated T cells.
| Materials and Methods |
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Lewis rats were purchased from Seiwa (Fukuoka, Japan) and used at 812 wk of age. Chronic relapsing EAE was induced by immunization of rats with 200 µl of guinea pig spinal cord homogenate in CFA (Mycobacterium tuberculosis H37Ra, 5 mg/ml) as described previously (13) with a few modifications. One gram of spinal cord tissue was homogenized in 1 ml of PBS, and the suspension was emulsified with an equal volume of CFA. Starting from the day of immunization, rats were given i.p. injections of cyclosporin A (Sandoz, Tokyo, Japan) at a dose of 4 mg/kg three times a week until day 21 postimmunization (PI). Acute EAE was induced by immunization with guinea pig MBP as described previously (14). Each rat was injected in the hind footpads on both sides with an emulsion containing 100 µg of guinea pig MBP in CFA. The clinical severity of EAE was divided into four stages (grade 1, floppy tail; grade 2, mild paraparesis; grade 3, severe paraparesis; grade 4, tetraparesis or moribund condition) (15). In this study, tissue sampling was performed at the early (day 1012 PI), peak (day 1315 PI), and recovery (day 2123 PI) stages of acute EAE and at the first attack (day 1417 PI), remission (day 2023 PI), second attack (day 2527 PI), and full recovery stage (day 3437 PI) of chronic relapsing EAE. Under ether anesthesia, blood was aspirated via cardiac puncture, and the whole spinal cord was removed. PBL and spinal cord T cells were then isolated by proteolytic enzyme treatment and the density gradient method as described previously (16).
Immunohistochemical staining
A single immunoperoxidase staining was performed using mAbs against TCR Vß8.2 (R78), Vß8.5 (B73), and Vß10 (G101) (17) as described previously (14). Briefly, frozen sections of the spinal cord were air-dried and fixed in ether for 10 min. After incubation with normal horse serum, sections were allowed to react with mAb, biotinylated horse anti-mouse IgG (Vector, Burlingame, CA), and horseradish peroxidase (HRP)-labeled Vectstain Elite ABC Kit (Vector). HRP binding sites were detected in 0.005% diaminobenzidine and 0.01% hydrogen peroxide.
cDNA synthesis and PCR amplification
RNA was extracted from PBL and spinal cord T cells using RNAzol
B (Biotecx Laboratories, Houston, TX). cDNA was then synthesized by
reverse transcription with SuperScript Preamplification System (Life
Technologies, Gaithersburg, MD) and amplified in a thermal cycler
(Perkin-Elmer, Norwalk, CT) using primer pairs for TCR. Cycling
conditions for PCR and nested PCR were as follows: 95°C for 10 min
for denaturation and hot start, 55°C for 1 min for annealing, and
72°C for 1 min for extension followed by 40 cycles of 95°C for 1
min, 55°C for 1 min, and 72°C for 1 min. Primers for Vß120 were
the same as those used in the previous study (9). Two types of Cß
primers, Cß outer (5'-TGTTTGTCTGCGATCTCTGC-3') and Cß inner
(5'-TCTGCTTCTGATGGCTCA-3'), were used in this study. Primers for V
which were the same as those used in the previous study (18) and two
types of C
, C
outer (5'-AGGGTGATGTTATCAGACTGG-3') and C
inner (5'-GGATCTTTCAGCTGGTACACA-3'), were used for TCR
-chain
analysis. C
and Cß primers were labeled with Cy-5 or rhodamine or
remained unlabeled.
CDR3 spectratyping
CDR3 spectratyping was performed as described previously (19)
with a few modifications. Three individual rats were examined at each
time point. cDNA was amplified with V
- or Vß-specific and
rhodamine-labeled V
or Cß outer primers, and undiluted or diluted
PCR products were added to an equal volume of formamide/dye loading
buffer and heated at 94°C for 2 min. Two microliters of the samples
were applied to a 6% acrylamide sequencing gel. Gels were run at 30 W
for 3 h 30 min at 50°C. Then, the fluorescence-labeled DNA
profile on the gel was directly recorded using FMBIO fluorescence image
analyzer (Hitachi, Yokohama, Japan). Spectratypes revealed by this
analysis usually consisted of five to seven bands. We designated each
band as I, II, or III in order of molecular size; e.g., the band
representing the smallest Vß8.2 PCR products was Vß8.2 band I.
Sequencing of PCR products
cDNA in PCR products or isolated from bands (in most cases, band I) on the acrylamide gel was reamplified with Vß and unlabeled Cß inner primers. Then, PCR products were ligated into pT-Adv vector and cloned using the AdvanTAge PCR Cloning Kit (Clontech Laboratories, Palo Alto, CA) according to the manufacturers instructions. The plasmid DNA was then sequenced using Cy5-labeled Cß inner primer and Autoread Sequencing Kit on a ALFexpress DNA sequencer (Pharmacia Biotech, Tokyo, Japan). CDR3 length is defined as a region starting from an amino acid residue after the CASS sequence of most Vß segments and ending before the GXG box in the Jß region as described previously (20).
| Results |
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In MBP-induced acute EAE, Vß8.2+ T cells are the
predominant population in spinal cord T cells throughout the course of
the disease (9). We wished to know whether Vß8.2 predominance is
observed in chronic relapsing EAE induced by immunization with spinal
cord homogenate. For this purpose, spinal cord sections taken from rats
at various stages of EAE were immunohistochemically stained using
currently available Vß-specific mAbs, and the proportion of
Vß8.2+, Vß8.5+, and Vß10+ T
cells was determined by counting stained cells. As shown in Fig. 1
, Vß8.2+ T cells were the
largest population among three phenotypes at all the stages examined.
It is of interest to note that although the number of
Vß8.5+ and Vß10+ T cells roughly paralleled
the clinical course, that of Vß8.2+ T cells remained
relatively unchanged during the remission, second attack and recovery
stage after a steep decline after the first attack (Fig. 1
).
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For comparison, CDR3 spectratyping analysis was performed using T
cells isolated from the spinal cord of a rat with MBP-induced acute
EAE. A typical spectratype pattern is shown in Fig. 2
. As reported previously (6) and
confirmed here, oligoclonal expansion of Vß8.2 and Vß17 TCR with
the shortest CDR3 (band I) (arrow and arrowhead in Fig. 2
, respectively) was obvious at this stage. However, only Vß8.2 showed
persistent expansion throughout the course of acute EAE (data not
shown). Using spinal cord T cells isolated from rats during chronic
relapsing EAE, CDR3 spectratyping was performed and the spectratype
pattern was compared with that obtained in acute EAE (Fig. 3
, AD). It is
clearly demonstrated that Vß8.2 band I was markedly expanded during
the first attack (arrow in Fig. 3
A). In addition, there was
oligoclonal expansion of Vß12 band I (open arrow in Fig. 3
A). Expansion of Vß8.2 band I persisted during the
remission phase, while that of Vß12 band I was not recognized at this
stage (Fig. 3
B). In Fig. 3
B, there was
oligoclonal expansion of Vß19 band I (arrowhead), but this finding
was observed only in one of three rats examined. The spectratype
pattern at the second attack was similar to that at the first attack in
which both Vß8.2 and Vß12 band I was clonaly expanded (arrow and
open arrow in Fig. 3
C). Vß8.2, but not Vß12, band I
expansion was still noticed at the full recovery stage (Fig. 3
D).
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-chain repertoire at the first and second
attacks of the disease. As shown in Fig. 4
6 and
V
23 was observed at the first attack (arrows). A similar finding was
obtained at the second attack (data not shown).
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We then extracted cDNA from Vß8.2 and Vß12 band I which showed
oligoclonal expansion, amplified it by nested PCR, then cloned and
determined the nucleotide sequences of the CDR3 region of each clone
(Tables I and
II). During the first attack, the most
frequently found sequence in Vß8.2 band I was DSSYEQYF (58.3%)
(Table I
) which is reported to be the representative sequence of
in vitro-established MBP-specific encephalitogenic T cell clone (7).
The percentage of this sequence in Vß8.2 band I at the remission
increased to 75% (Table I
). Interestingly, the predominance of the
DSSYEQYF sequence remained unchanged during the second attack and
became more marked at the full recovery stage (Table I
). We also
sequenced the CDR3 region of clones derived from Vß12 band I (Table II
) during the first and second attacks. Quite unexpectedly, the
predicted amino acid sequence of the CDR3 region of the most frequently
found Vß12 clones was identical to that of Vß8.2 clones, i.e.,
DSSYEQYF. However, the predominant Vß12 clone isolated at the first
attack is not the same as that found at the second attack because the
nucleotide sequence of these clones was different (Table II
).
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We also examined the spectratype pattern of TCR of PBL (Fig. 5
). Since the CNS lacks the lymphatic
system, precursor cells may enter the CNS via the blood stream. CDR3
size spectratyping was performed at the first attack, remission, second
attack, and full recovery stages using PBL. Unlike spinal cord T cells,
oligoclonal expansion was marked only in Vß8.2 TCR (data not shown).
As shown in Fig. 5
, Vß8.2 band I expansion was observed during the
first and second attacks in PBL as seen in the spinal cord. However,
this EAE-specific spectratype pattern was not visible in PBL at the
remission and full recovery stage.
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| Discussion |
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We first determined the number of T cells bearing different Vß
phenotypes using currently available Vß-specific mAbs (Fig. 1
). As
previously demonstrated by us (9) and others (10), Vß8.2+
T cells infiltrate the CNS at the early stage of MBP-induced acute EAE
and become a predominant population. If Vß8.2 predominance is not
observed in the spinal cord of rats with chronic relapsing EAE induced
by immunization with spinal cord homogenate, then encephalitogenic Ags
other than MBP would be involved. However, this was not the case. As
clearly shown in this study, Vß8.2+ T cells are the
predominant population throughout the course of chronic relapsing EAE,
suggesting that Ag involved in chronic EAE is similar to that in acute
EAE.
CDR3 spectratyping analysis revealed that EAE-specific spectratype pattern, i.e., oligoclonal expansion of Vß8.2 with the shortest CDR3 (band I), was found in the spinal cord throughout the course of chronic relapsing EAE and that it was essentially the same as that of acute monophasic EAE (6). Furthermore, determination of nucleotide and amino acid sequences showed that the CDR3 region of the majority of clones constituting Vß8.2 band I was the same as that of MBP-specific encephalitogenic T cell clones (7, 8) and remained unchanged as the disease progressed. The most straightforward explanation for these findings is that in chronic relapsing EAE of this type, encephalitogenic Ag is not switched from one to another and is similar to that of acute EAE, possibly MBP. Another characteristic finding was oligoclonal expansion of Vß12 band I of spinal cord T cells. Vß12 band I expansion was observed in the spinal cord, and not in PBL, only at the active stage of the disease (during the first and second attacks). Furthermore, the most frequently found CDR3 amino acid sequence was identical to that of Vß8.2. Although the exact function of T cells bearing this spectratype remained to be elucidated, we consider at the moment that they act as additional effector cells which are activated during active stages of chronic relapsing EAE. The possibility that they are regulatory T cells seems to be less likely because Vß12 band I expansion was not observed at the recovery stage. Collectively, these findings suggest that upon immunization with CNS homogenate including heterogeneous Ags, T cells recognize the major component of encephalitogens, expand and develop EAE lesions.
We have also examined TCR
-chain by CDR3 spectratyping. Our
previous studies regarding the V
repertoire in acute EAE revealed
that V
1 and V
2 expansion was observed at preclinical and early
stages, whereas that of V
23 was detected mainly at the clinical
stages (G. Kim, K. Kohyama, N. Tamuma, and Y. Matsumoto, unpublished
data). Thus, the use of V
-chain by spinal cord T cells is not
strict compared with that of Vß-chain. In the present study, we found
that V
6 and V
23 showed oligoclonal expansion at the first and
second attacks of chronic relapsing EAE. Therefore, preferential usage
of V
23 by spinal cord T cells is the same finding in both acute and
chronic relapsing EAE although V
6 expansion was not observed in
acute EAE. These V
s are thought to pair with Vß8.2 or Vß12,
which expanded oligoclonally in chronic relapsing EAE. However, it is
also possible that multiple chains are expressed on a single cell as
reported previously (21, 22). Very recently, Wang et al. (23)
reported very interesting findings with regard to the role of
TCR
- and ß-chains in Ag specificity. Using mice carrying single
V
-chain (a TCR
-chain transgenic mouse in a TCR
-deficient
background), they found that a specific amino acid residue of ß-chain
plays a critical role in determining the specificity of TCR-Ag
interactions. The fact that different TCR Vßs possess highly
preserved sequences in the CDR3 region suggest that polyclonally
activated T cells in the CNS recognize the same or structurally similar
Ags during the course of the disease.
Analysis of PBL by CDR3 spectratyping also revealed an interesting
finding with regard to relapse of EAE. As clearly shown in Fig. 5
, Vß8.2 band I expansion in PBL was observed at the first and second
attacks, but not at the remission and full recovery stage. In addition,
the majority of TCR clones comprising this band possessed EAE-specific
sequence in their CDR3 region (our unpublished data). These findings
imply that encephalitogenic T cells are activated in the lymphoid organ
and supplied via the blood stream to the CNS only during the clinical
phase of the disease. Recently, it was demonstrated that myelin protein
expression is increased in lymph node at a later stage of chronic
relapsing EAE resulting in reactivation of encephalitogenic T cells
(24). This event may correspond to reexpansion of Vß8.2 band I in
PBL.
In the present study, we analyzed a complete set of TCR ß-chain family of spinal cord T cells and PBL of Lewis rats with chronic relapsing EAE by CDR3 spectratyping and then determined the nucleotide sequences of the spectratype-derived CDR3 of interest. We show here that EAE-specific spectratype pattern in the spinal cord remains unchanged throughout the course of the disease, thus strongly suggesting that encephalitogenic epitope recognized by T cells is not changed during the course. When considering TCR-based immunospecific therapy for MS patients, CDR3 spectratyping analysis is indispensable to obtain important information.
| Acknowledgments |
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| Footnotes |
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2 Address correspondence and reprint requests to Dr. Yoh Matsumoto, Department of Neuropathology, Tokyo Metropolitan Institute for Neuroscience, Musashidai 2-6 Fuchu, Tokyo 183-8526, Japan. E-mail address: ![]()
3 Abbreviations used in this paper: MS, multiple sclerosis; CNS, central nervous system; MBP, myelin basic protein; CDR3, complementarity-determining region 3; EAE, experimental autoimmune encephalomyelitis. ![]()
Received for publication March 24, 1998. Accepted for publication August 28, 1998.
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chains on the surface of T cells in T cell receptor transgenic mice. J. Exp. Med. 178:1807.
chains: dual receptor T cells. Science 262:422.This article has been cited by other articles:
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