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*
Institut National de la Santé et de la Recherche Médicale, Unité 437, "Immunointervention dans les Allo et Xénotransplantations" and Institut de Transplantation et de Recherche en Transplantation, Centre Hospitalier Universitaire Hotel Dieu, Nantes, France;
Etablissement de Transfusion Sanguine, Nantes, France;
Harvard Medical School, Beth Israel, Deaconess Medical Center, Boston, MA 02215;
§
Service dAnatomopathologie, Centre Hospitalier Universitaire Hotel Dieu, Nantes, France; and
¶
Service de Virologie, Institut de Biologie, Nantes, France
| Abstract |
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| Introduction |
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Acute rejection is histologically characterized by an intense and destructive leukocytic inflammation of graft tissues with a predominant Th1 cell type in the graft infiltrate (9). Alloreactive T cells involved in acute allograft rejection predominantly recognize donor MHC Ags on donor APC ("direct" pathway). In contrast, recognition of donor determinants presented by recipient APC ("indirect" pathway) is more likely to be involved in long-term rejected grafts (see Ref. 10 for review). Alloreactive T lymphocytes derived from acutely rejected human kidney allografts were shown (by amplification of the Vß transcripts (11, 12) and Southern blot-based studies (13)) to exhibit some restricted repertoire. In addition, a bias in TCR fragment usage, in all cases involving Vß8, was detected in 14 of 19 cases of kidney transplant recipients when using mAbs against different Vß families (14). However, these studies were performed following in vitro culture and after stimulation (11, 13) and therefore may not reflect the in vivo situation. In addition, biopsy material of limited size, which has provided a better understanding of cellular transplant immunity (15), may favor clonal expansion (16). Because the occurrence of acute rejection episodes is highly predictive of chronic rejection, alloreactive T cells could represent the common immunological link between these two pathological entities. This is also suggested by the role of T cells in graft neointima formation in CR (17).
Diversity of the TCR (18)
ß is generated by random
combination of V, (D), J, and C region segments, nibbling of junctional
V, (D), and J regions, addition of nontemplate nucleotides, germlime
polymorphism between individuals, and pairing of one
-chain with one
ß-chain (19). The complementary determining region 3
(CDR3), the hypervariable region that carries most of the fine
specificity of Ag recognition by T cells, varies in length due to the
addition or removal of nucleotides at the VD and DJ junctions by
nucleotide transferases during the recombination process. Therefore,
analysis of CDR3 lengths and sequences would indirectly reflect the
selection of the T cell repertoire usage by alloreactive T cells
involved in CR and may bring new and important information concerning
the mechanism of this poorly understood process to light
(20). In this paper, we report on an analysis of T cell
infiltration and, for the first time, on the variations of Vß T cell
repertoire usage at the CDR3 level in transplantectomy pieces from 18
human kidney-graft recipients with a clinical history and histological
lesions of long-term CR with or without superimposed histologically
acute lesions. Our findings show that a highly altered T cell response
is involved in CR with superimposed acute lesions and suggest the
presence of a restricted set of Ags.
| Materials and Methods |
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We analyzed a population of 18 kidney recipients who underwent
transplantation between 1983 and 1996 and who were transplantectomized
due to a chronic graft dysfunction, all with characteristic
histological lesions of CR (Table I
). The
mean graft survival was 69.8 ± 38.8 mo (range, 6126). The time
interval between graft loss (initiation of chronic dialysis) and
transplantectomy was 243 ± 248 days (range, 0750). Fourteen
patients received a first kidney graft, twice combined with a pancreas.
The mean recipient age at grafting was 39.1 ± 17.5 years (range,
866). Eleven recipients (66%), vs 14 donors (78%), were male. The
initial disease was a glomerulonephritis in nine patients, three had
urological malformations, one a vascular disease, and five were not
histologically characterized before grafting. Twelve patients had no
"historical" anti-T panel-reactive Abs (PRA) before grafting,
five patients had anti-T PRA between 4 and 58%, and only one was
hyperimmunized, with a PRA level above 75%. Sixteen patients received
an induction therapy consisting of anti-thymocyte globulins or
anti-lymphocyte globulins (Pasteur-Mérieux et Vaccins, Lyon,
France), one received an anti-IL-2 receptor mAb (21),
and one received HLA-derived peptide (Allotrap; Sangstat Medical
Corporation, Menlo Park, CA) (22). Ten patients (55%)
presented at least one early acute rejection episode, three presented
two episodes, and one presented four episodes. All were CMV
seronegative before grafting. During the follow up, six patients (33%)
were treated for an overt CMV disease. CMV infection was detected in
peripheral blood leukocytes 13 mo after grafting, either by CMV
antigenemia assay (n = 4) or by amplification of
CMV-DNA (n = 2) depending on the length of the survey.
At transplantectomy, patients had been free of immunosuppressive
therapy for 12 ± 9 mo, except for four who received cyclosporin A
(n = 1), cyclosporin A and azathioprine
(n = 1), prograf (n = 1), or steroids
(n = 1). Histologically, according to the Banff
classification (3), CR lesions were observed in all
patients (grades II, III), associated with significant superimposed
acute lesions in 14 of them (types I, II, III) (Table I
). None of the
18 patients had a recurrent disease on the transplant. PBMC, collected
at the day of but before grafting from five recipients, were also
available and used for the analysis of the ß-chain repertoire.
Finally, TCR ß-chain repertoires were also studied using resting PBMC
from healthy volunteers. PBMC were isolated by density gradient
(Eurobio, Les Ullis, France), according to standard
procedures.
|
Transplantectomy pieces from long-term rejected kidney
allografts were immediately snap-frozen in liquid nitrogen, embedded in
OCT compound (Tissue Tek; Miles Laboratories, Elkhardt, IN), and stored
at -80°C until used for immunohistology. Immunoperoxydase staining
of 5-µM sections of frozen tissue was performed as follows: sections
were cut, fixed in acetone, and labeled using a three-step indirect
immunoperoxydase technique (23). Primary Abs were the
following mouse IgG anti-human mAbs: anti-CD3 (Dako, Trappes,
France), anti-CD11b, anti-CD16, anti-CD19, anti-HLA-DR,
anti-RIL-2, and anti-TCR PAN
/
(Immunotech, Marseille,
France). All of these Abs were used at the dilution recommended by the
manufacturer. The mouse mAb directed against human TCR
- and
-chain determinants was pretested on human lymph nodes as a positive
control to predetermine the optimal dilution. The nonspecific staining
was taken into account by omission of the first Ab. The secondary Ab
used was a biotin-conjugated anti-mouse IgG (Vector Laboratories,
Burlingame, CA). Finally, tissue sections were incubated with HRP
streptavidin (Vector Laboratories) and developed with "intense
purple" (VIP kit; Vector Laboratories).
The area of each immunoperoxydase-labeled tissue section that was infiltrated by cells was determined by quantitative morphometric analysis (24, 25). Briefly, positively stained cells in the interstitium of each section were counted by morphometric analysis using a point counting method with a 121-intersection squared grid in the eyepiece of the microscope. Results were expressed as the percentage of area infiltrate of each graft section occupied by cells of a particular antigenic specificity (±SD). The percentage of area infiltrate was calculated as follows: [(number of positive cells under grid intersections) ÷ (total number of grid intersections = 121)] x 100. The graft sections were examined at a magnification of x400. The accuracy of the technique is proportional to the number of points counted. Thus, to maintain a SD of <10%, 15 fields were counted for each labeled section of high density and 40 fields for sections with low density (<10%). Point counting was scored by two observers.
RNA extraction and cDNA synthesis
Total RNA from kidney transplantectomies was isolated by the guanidium isothiocyanate procedure and purified on a cesium chloride gradient (26). Total RNA from PBMC was extracted by the Chomczynski and Sacchi method (27). Before retrotranscription, RNA samples were systematically treated with DNase (Promega, Charbonniéres, France). Ten micrograms of RNA were reverse-transcribed into cDNA using 14 µg/ml of oligo(dT)12- 18, 10 mM DTT, 0.5 mM of each dNTP, 40 U RNAsin (Promega), and 200 U M-MLV reverse transcriptase in 5x first-strand buffer (Life Technologies, Gaithersburg, MD). The cDNA synthesis reaction was brought to a final reaction volume of 100 µl.
TCR ß-chain CDR3 fragment size determination and sequencing
PCR amplification and elongation reactions for analysis of the CDR3 lengths. Aliquots of the cDNA synthesis reaction (2 µl) were amplified in 50-µl reactions with 1 of the 20 Vß human family-specific primers and a Cß primer recognizing both Cß1 and Cß2 regions (28, 29). The Vß10, 20, 21, and 24 families were not represented because no transcripts were available. The PCR amplification conditions were as previously described (30). Aliquots (2 µl) of the 20 unlabeled Vß-Cß PCR products were then subjected to elongation with either Cß or 13 Jß fluorophore-labeled specific primers using the same PCR conditions as previously described (30). The elongation reaction products were then heat-denatured and loaded onto a 6% acrylamide, 8 M urea gel and run on an ABI 373A DNA sequencer (Applied Biosystems, Foster City, CA) for size and fluorescence intensity determination.
TCR Vß chain transcript sequencing. When common and dominant Vß-Jß expansions were found, the Vß transcripts were then reamplified for 35 cycles with one of the 13 unlabeled Jß primers (0.5 µM) using the same PCR conditions as described above. Amplification products (2 µl) were then ligated into the PCR topo vector of the Topo Ta Cloning Kit (Invitrogen, Carlsbad, CA) in accordance with the manufacturers instructions. The ligation product was transfected into Top10F' competent cells (Invitrogen). Twenty white growing colonies (containing individual clones) were randomly selected. Plasmid DNA was then recovered by the alkaline lysis method and digested with EcoRI to confirm insertion of clones. Forty microliters of plasmid DNA were purified, and 5 µg of the preparation were lyophilized and sequenced using standard methods (Appligene, Illkirch, France).
Analysis of TCR repertoire alterations
Several approaches were used. The Immunoscope software (28) was used to obtain a semiquantitative analysis of the ß-chain of the TCR repertoire at the CDR3 level. The distribution profile of CDR3 lengths in base pairs for each Vß family was represented, typically with 711 peaks each separated by 3 nt. Each peak corresponds to a TCR transcript with a given CDR3 length that may contain multiple sequences. The number of TCR transcripts with a specific CDR3 length is proportional to the area under each peak. An increase in the height and area of a size peak usually signals an oligoclonal or monoclonal expansion in the polyclonal T cell background. An oligoclonal expansion with the same dominant CDR3 length shared by several individuals is defined as common. When only one sequence is found for the same CDR3 length, the peak signals a monoclonal expansion, which is defined as "public" if reproducibly found in several samples.
The Reperturb software (25, 31) was used to further identify and quantify the alterations in CDR3 length distributions of each Vß family and in each sample. Briefly, each CDR3 profile obtained using the Immunoscope software was translated into a probability distribution using the fraction of the area under the profile for each CDR3 length, as described in detail elsewhere (25, 31). A control profile, representing the unaltered Gaussian repertoire, was established for each Vß family by calculating the average probability distribution for the corresponding Vß in PBMC of three healthy volunteers. The average of these distributions, for each Vß family separately, was then used as a control distribution for analysis of the other samples. The alterations in each Vß family were defined as the sum of the absolute values of difference for all CDR3 lengths in that profile. The sum of the alterations in the 20 Vß families studied in a sample gives the alterations in the entire Vß TCR repertoire in this sample. Differences between controls and patients were statistically assessed using the Students t test, significance being established at p < 0.05.
Relative quantification of Vß transcripts
Principle. The ABI PRISM 7700 Sequence Detection Application program (Applied Biosystems) is used to detect and measure fluorescence emitted during PCR amplification of a given target sequence in a 96-well reaction plate. This detection is conducted in real-time because data is collected during each PCR cycle. Fluorescence is emitted following binding of the dye labeler, SYBR Green, to double-stranded DNA (32). Thus, the level of fluorescence is directly proportional to the level of PCR product. Samples are measured as well as a standard prepared using a dilution range of the same target sequence, from which a standard curve is derived. Using this standard curve, the quantity of the target sequence in samples is calculated. Normalization of the levels of the target sequence is then conducted using a reference house-keeping gene. In this case, the levels of each Vß family were measured separately and were normalized against the level of Cß, which is a reference gene for T cells (33).
Oligonucleotides and standard construction.
To prepare each Vß standard curve, the respective Vß primer (Vß1,
5, 8, 13, 14, 16, 18, 19, 23) was used in the forward position together
with the Cßr primer in the reverse position (Table II
and Fig. 1
). To prepare the Cß standard curve,
the Cßf and Cßr primers were used in the forward and reverse
positions, respectively (Table II
and Fig. 1
). The target sequence was
amplified in cDNA derived from a healthy volunteer using forward (one
Vß or Cßf) and reverse (Cßr) oligonucleotides, which were
electrophoresed and purified using a gel extraction kit (QIAquick Gel
Extraction Kit; Qiagen, Germany). For each Vß family and Cß, the
standard concentration was derived from its absorbance value at 260 nm,
and the number of copies per ml was then calculated using the m.w. of
the cDNA. Subsequent dilutions of each Vß and Cß standard DNA were
performed to obtain 107,
106, 105,
104, 103, and
102 copies per well to establish a range of
concentration similar to that of the target in the biological
samples.
|
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Detection of virus genome
PCR assays were used to detect the presence of DNA of the HSV (34), human herpes virus 6 (HHV6) (35), EBV (36), CMV (37), and human papillomavirus (38) in long-term rejected kidney allografts. EBV lytic-phase Zebra mRNA in the grafts was also analyzed by reverse transcription and PCR amplification (39).
| Results |
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ß+ T lymphocytes are, together with monocytes and
macrophages, the predominant cell type in long-term rejected kidney
allografts
Subtypes of inflammatory cells in the area infiltrate, including T
lymphocytes, were quantified in 18 long-term rejected kidney human
allografts with CR, either associated (n = 14) or not
associated (n = 4) with superimposed acute lesions at
Banff scoring. Chronically rejected kidneys with superimposed
histologically acute lesions displayed an area
infiltrate represented by 35 ± 10% of T lymphocytes
(CD3+), 17 ± 10% of monocytes-macrophages
(CD11b+), 20 ± 10% of B lymphocytes
(CD19+), and 1.8 ± 0.6% of NK cells
(CD16+), as quantitatively assessed by the point
counting method (Fig. 2
). Chronically
rejected kidneys with restricted CR lesions showed an area infiltrate
composed of 30 ± 7% T lymphocytes, 35 ± 9%
monocytes-macrophages, 20 ± 9% B lymphocytes, and 1 ±
0.4% NK cells (Fig. 2
). However, despite a roughly similar number of
mononucleated cells (i.e., T/B lymphocytes plus monocytes/macrophages)
infiltrating kidneys with CR or CR with acute lesions on frozen
sections (immunochemistry), only Banff scoring discriminates the
"active infiltrate," particularly tubulitis, restricted to kidneys
with superimposed acute lesions.
|

T lymphocyte expansion has been reported in
some acutely rejected human kidney allografts (40) and in
PBMC of CMV-infected patients (41), we also examined the
presence of this T lymphocyte subtype in the grafts. Less than 0.1% of
T lymphocytes were stained by anti-PAN
/
TCR (Fig. 2
-chain
activation marker was expressed in only a few cells (8 ± 6% and
9 ± 5%, respectively). Highly altered Vß-Cß repertoire in chronically rejected human kidney allografts with superimposed histologically acute lesions
The length of the CDR3 region in each Vß family, in patients and
healthy volunteers, was amplified using specific primers for the Cß
and 20 Vß human families. The degree of alteration in the T cell
repertoire was further studied using the Immunoscope and Reperturb
softwares. Fig. 3
shows the Immunoscope
analysis of the CDR3 size distribution of 20 Vß families in the
transplant of a representative patient (patient CI), as compared with
PBMC from patient CI before grafting, as well as from a healthy
individual. The comparative analysis of CDR3 size for each Vß family
in pregraft PBMC showed a Gaussian distribution pattern (711 peaks),
similar to the healthy volunteer profile and characteristic of a
resting population. In contrast, the Vß patterns in the graft of the
same patient displayed numerous oligoclonal or monoclonal T cell
expansions in terms of CDR3 length (Fig. 3
).
|
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|
Oligoclonal expansions were present in several patients and
involved 11 Vß families. First, two common and dominant
rearrangements were found for the Vß1 (180, 183 bp), Vß5 (159, 162
bp), and Vß23 (272, 278 bp) families and were found in 5 (28%), 6
(33%) and 6 (33%) of 18 patients, respectively. Immunoscope profiles
for these three Vß families and for one representative patient are
shown in Fig. 6
A. Other
oligoclonal expansions with one dominant size rearrangement were also
shared by several patients and involved Vß8 (271 bp, patients VJ, BC,
LJM, MP, MC, CC, GM), Vß11 (140 bp, patients TS, BA, DF, PE, CI),
Vß13 (327 bp, patients VJ, BC, LJM, LB, MP), Vß14 (258 bp, patients
MC, CK, GM), Vß15 (174 bp, patients TS, VJ, BC, CI, BR, MR), Vß16
(136 bp, patients TS, BR), Vß18 (200 bp, patients CK, MP, BR), and
Vß19 (153 bp, patients PE, BR). Representative profiles are shown in
Fig. 6
B. These common rearrangements were predominantly
found in patients with CR associated with superimposed acute lesions.
Nevertheless, no correlation was found between these oligoclonal
responses and degree of HLA compatibilities, donor/recipient HLA
specificities, history of CMV disease, presence of viral genome in the
graft (see later), sex matching, time between graft loss and
nephrectomy, or number of acute rejection episodes.
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|
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Because oligoclonal Vß-Cß or Vß-Jß expansions could be
correlated to viral infections (31, 42, 43), we also
examined, by PCR amplification, the presence of CMV, HSV, HHV6, human
papillomavirus, and EBV genome in long-term rejected kidneys. Some
viral DNA was detected in the grafts, involving CMV (patient VJ), HSV
(patient PE), HHV6 (patients MR, LB, TS), and EBV (patients MR, CC, VJ,
LB, CI, PE, BC, MC, DD). Only one kidney (patient BC) presented EBV
lytic-phase mRNA. However, no significant correlation
(
2 test) could be found between the presence
of a Vß-Cß or a Vß-Jß common and oligoclonal expansion and the
presence of a viral genome in the grafts.
Vß transcripts of altered patterns accumulated in CR with superimposed histologically acute lesions
Because the level of expression of a given mRNA species could be
even more important than its qualitative Immunoscope profile and gives
further information on the magnitude of the selective pressure on the
Vß repertoire, we quantified by PCR (SYBR Green methodology, see
Materials and Methods) the accumulation of the altered Vß
transcripts in the grafts, with primers devoted to nine Vß families.
Vß/Cß transcript ratios were found to be variously increased in the
grafts as compared with the ratios observed in the PBMC of healthy
volunteers, except for the Vß13 family (Table IV
). The average quantity of Vß8/Cß
transcripts in the grafts from patients VJ, BC, LB, and MP who
presented a Vß8-Jß1.4 oligoclonal expansion was five times higher
than other patients without this rearrangement (Table IV
). However,
transcripts of some common expansions such as Vß8 (see patient MP in
Table IV
and his corresponding Immunoscope profile in Fig. 7
A) were 120 times higher than in pregraft PBMC or in
healthy volunteers.
|
| Discussion |
|---|
|
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ß+ T
cells infiltrating long-term rejected kidney allografts exhibit a
strongly altered TCR Vß usage particularly when CR is associated with
superimposed histologically acute lesions. Moreover, besides vigorously
skewed "private"-type TCR biases, common and oligoclonal Vß-Cß
rearrangements were also frequently observed. In contrast, transplants
presenting a restricted CR at histological Banff grading displayed a
resting-type Gaussian TCR profile that, together with the absence of an
"active" infiltrate (i.e., tubulitis) in this CR-restricted
pattern, does not suggest a major involvement of T cells in this
specific process. Our data suggest that a few antigenic determinants
only may stimulate the immune system of recipients of long-term kidney
grafts. The analysis and understanding of the T cell repertoire alterations involved in local or systemic responses has been crucial in several clinical situations including alloimmunity, tumor immunity, autoimmune, and infectious diseases. For instance, oligoclonal T cell expansions at the CDR3 level have been reported in melanoma tumors (30), in skin lesions of acute graft-vs-host disease (44) and in synovial lesions from patients with rheumatoid arthritis (28). However, despite most of these studies not using the Reperturb approach to quantify and compare the average global TCR alterations, their magnitude, as assessed by the number of affected Vß families and of common oligoclonal expansions (i.e., shared by several patients) for a given Vß-Cß (or Vß-Jß) rearrangement, was much less remarkable. Only one report on TCR alterations during AIDS progression, using the same method of assessment of total alterations of nine Vß families, showed a comparably strongly altered pattern, but without a common profile being shared between patients (31), a frequent characteristic in our study of long-term rejected grafts.
Restricted or altered Vß repertoires of T lymphocytes infiltrating kidney allografts during acute and chronic rejection have been already described in humans but with semiquantitative PCR or by Southern blot methods that do not discriminate CDR3 biases within each of the Vß families (11, 12, 13, 45). Barth et al. have shown that the TCR repertoire in biopsies of acutely or chronically rejected kidney allografts was restricted to one to three dominant Vß families, without public expansions (12). However, in these reports of overrepresentation of some Vß families, the fact that the tissue samples used were biopsies casts a doubt on their relevance in representing the actual global alterations in a graft. Indeed, focal T cell clonal expansion may be selected by the use of very small tissue samples, likely not representative of the total immune response occurring in a graft (11, 13, 16, 46). In addition, most of these studies were performed on alloreactive T cell lines derived from grown graft-biopsy infiltrating cells (11, 13, 46). Despite the fact that one cannot exclude that the in vitro step allows the most relevant alloreactive cells to emerge from the heterogenous infiltrate, it is highly likely that a selection operates during the culture, generating biases per se, and that again, the overall observed pattern may not reflect the in vivo situation. Other artifactual biases can be further amplified by the use of polyclonal stimuli in the culture, promoting uncommitted cells. Moreover, Hall and collaborators have shown that alloreactive clones derived from rejected kidney grafts presented an altered TCR repertoire that was positively correlated with the length of time cells were maintained in culture (11). In contrast, in our study, we directly amplified transcripts of Vß families from large pieces of surgically removed grafts (without a culture step) to reflect as much as possible the in vivo situation.
Interestingly, the TCR Vß repertoire of kidneys that underwent slow functional degradation with histological lesions fitting with the definition of CR only (i.e., without superimposed acute lesions) presented a Gaussian pattern of Vß family CDR3 lengths, which usually reflects uncommitted T lymphocytes at the resting stage, can also be observed in the context of a strong polyclonal activation (25). However, despite a roughly similar number of mononucleated cells found in kidneys with restricted CR and in CR with superimposed acute lesions, the absence of "active" localization of T cell infiltrate (i.e., tubulitis) in restricted CR patterns does not favor such an alternative. Rather, our data strongly suggest that T cells may not be involved in this restricted CR process and that other nonimmunological factors (initial nephron load, blood pressure, hyperlipemia, drug related chronic toxicity) may operate in this situation (2). The superimposed histologically acute lesions associated with CR bring some semantic complexities to the interpretation of our findings because the pattern could be more related to late acute rejection rather than to restricted CR. However, it is noteworthy that most of these kidneys were removed several years after grafting (11 of 14 after 4 years) and that such a profile is likely to be restricted to the indirect pathway of allorecognition (47) and not to direct recognition of donor MHC motives. Therefore, the superimposed histologically acute lesions are likely to reflect an emphasized indirect recognition process that would not have the possibility to emerge when a normal immunosuppressive regimen was still being administered. In this context, such transplants might be characteristic of the processes operating in long-term kidneys and would allow an interesting basis for characterization of the relevant Ags involved, which for now remain elusive.
Allorecognition occurring through the indirect (or cross-priming) pathway can proceed from a variety of peptides from donor MHC, graft tissues, or microorganisms. However, no correlations between oligoclonal alterations and donor sex, donor or recipient MHC alleles, or MHC incompatibilities were noted. Could donor T cells have contributed to this pattern (i.e., altered Vß repertoire)? Thus far, there is no direct evidence available in the literature. However, donor cell chimerism has been detected years after kidney transplantation (48) at levels as low as 1:100,000 donor to recipient cells by PCR sequence-specific primers (SSP) using the Y chromosome as a target. In the present study, no circulating donor cells could be detected by PCR-SSP performed on HLA-DR targets in four patients for whom PBL harvested at the time of the experiment were available (patients CS, LJM, VJ, and DD, data not shown). Based on this finding, it is likely that the altered Vß repertoire observed in this study was due to recipient T cells alone.
Nonrestricted public CDR3 sequences found in the common Vß8-Jß1.4
alteration in several recipients does not preclude the possibility that
the corresponding Vß chains do not interact with identical
determinants. Indeed, the cross-reactive nature of TCR recognition is
now a well-accepted concept (49, 50), and situations where
TCR with similar CDR3 sequences interact with different peptides or,
alternatively, where Vß-chains of different CDR3 sequences interact
with a single determinant are increasingly reported (51, 52). Furthermore, identical Vß TCR sequences shared by T
lymphocytes infiltrating the graft of several animals, even in a
congeneic combination, were the exception (53, 54) and
were almost restricted to a single donor-specific transfusion-induced
tolerance (55). However, the above-mentioned high
cross-reactive nature of the TCR makes any interpretation at this stage
difficult, and one cannot exclude the fact that positively selected
clones with the observed Vß alterations could also recognize viruses
known to frequently infect long-term graft recipients. Highly altered
Vß repertoires with oligoclonal Vß expansions have also been
described in the peripheral blood of patients infected by HIV
(31), of healthy individuals infected by EBV
(42), and in patients with chronic infection with
hepatitis B virus (43). Because CMV infections are
frequent after transplantation (8), oligoclonal and common
TCR expansions could also have been directed against CMV-derived
peptides. However, 
TCR clones have only been found to be
expanded during CMV infection (41), and 
-positive T
cells represented a tiny minority (<1%) of infiltrating cells in our
patients. Furthermore, we were unable to identify TCR-
ß
alterations mimicking the common and oligoclonal patterns found in the
grafts studied when peripheral TCR repertoires in four patients were
analyzed, with the same method, following an unambiguous overt CMV
disease. Finally, neither the clinical CMV infections nor the finding
of viral genome (CMV, HSV, HHV6, human papillomavirus, and EBV)
correlated with a Vß-Cß or a Vß-Jß oligoclonal expansion found
in the kidneys could sustain, at this stage, a rationale for the
hypothesis of viral-driven TCR alterations. Furthermore, none of the
published characteristics or sequences of virus-driven TCR alteration
reported in humans (42) were noted in the altered Vß
transcripts derived from the rejected grafts studied.
Nevertheless, it is noteworthy that the most altered family (with common Vß-Jß rearrangement) was found to be the Vß8 family. An increased Vß8 usage has been reported not only in an autoimmune disease with a potentially viral etiology (56), or following superantigen stimulation (57), but also in peripheral T lymphocytes of kidney graft recipients (14). However, no analysis of Vß CDR3 lengths or of association with specific Jß was performed in the referred studies. Furthermore, our study not only showed an altered Vß8 family profile, but also provided a quantitative indication of the strong accumulation of Vß8 mRNA (increased up to 120-fold), further suggesting a positive selection of the corresponding clones.
Finally, an elegant demonstration that in an experimental model of heart allotransplantation the presence of the chronically rejected grafts could elicit an autoimmune process by peptide molecular mimicry between donor MHC and parenchymatous motives (cardiomyosin) has been recently proposed in mice (58). In addition, the autoreactive responses, triggered by the graft, were, in turn, instrumental in worsening the CR process (58). Furthermore, chronic inflammatory lesions induce a local tissue stress response that may trigger additional T cell activation. Such T cell might react through stress protein-related mechanisms (59). Whether the strong skewed common Vß-Jß TCR repertoire we observed in long-term rejected kidneys is related to such a process also remains to be tested.
|
| Acknowledgments |
|---|
| Footnotes |
|---|
2 Address correspondence and reprint requests to Dr. Jean-Paul Soulillou. Institut National de la Santé et de la Recherche Médicale, Unité 437, 30 Boulevard Jean Monnet, 44093 Nantes Cedex 01, France. E-mail address: ![]()
3 Abbreviations used in this paper: CR, chronic rejection; CDR3, complementary determining region 3; HHV6, human herpes virus 6; PRA, panel-reactive Ab. ![]()
Received for publication August 27, 1999. Accepted for publication November 11, 1999.
| References |
|---|
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n
, M. Kessler, G. C. Faure. 1999. Increased usage of TCR Vß8 in kidney transplant recipients with aberrant immune reconstitution and clinical complications. Transplantation 67:1441.[Medline]
1-w29/Vß1-w24) for the study of human T cell receptor variable V gene segment usage by PCR. Eur. J. Immunol. 22:1261.[Medline]
/
antigen receptor in human renal allografts. Hum. Immunol. 36:11.[Medline]
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