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Departments of
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Immunology and
Molecular Biology and Biochemistry, Mayo Clinic, Rochester, MN 55905; and
hkl Research, Inc., Rochester, MN 55902
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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To address the issue of TCR degeneracy, we investigated MHC/peptide complexes found to be antigenic for the 2C T cell. The alloreactive 2C T cell recognizes Ld and Kbm3 murine class I molecules as alloantigens (12, 13), and the respective allopeptides, p2Ca and dEV-8, have been identified (5, 14). In addition, a third peptide, SIYR-8, has been identified from a degenerate synthetic peptide library, which is antigenic for the 2C T cell in the context of the Kb class I molecule (15). The addition of this third peptide to the set of peptide Ags strongly recognized by 2C is interesting because experiments with 2C TCR transgenic mice have revealed that the Kb class I molecule is necessary for positively selecting the 2C TCR (16). As 2C can bind a set of different MHC/peptide targets, we were interested in the specificities exhibited toward various combinations of peptide with the three MHC molecules. We found a degenerate recognition by 2C of all three peptides when presented in the context of the self-restricting element, Kb.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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T2 cells were transfected with Kb/Ld and Kbm3/Ld, respectively, using constructs described previously (17). T2 cells were provided by Dr. L. Sherman (The Scripps Institute, La Jolla, CA), T2Ld cells were supplied by Dr. P. Cresswell (Yale University, New Haven, CT), and RMA-S cells were provided by Dr. T. Hansen (Washington University, St. Louis, MO). T2 transfectants were maintained in 500 µg/ml G418.
Peptides
Peptides were synthesized using solid phase chemistry as
described previously with F-moc-protected L amino acids (18). Each
synthetic peptide was purified to a single homogeneous peak by reverse
phase HPLC (see Table I
for peptide
sequences).
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CTLs used in this study were either lines established from 2C transgenic mice (16) or the original 2C CTL clone (12) provided by D. M. Kranz (University of Illinois, Urbana, IL). Briefly, splenocytes from the transgenic mice or the 2C clone (DK) were stimulated weekly with lethally irradiated BALB/c stimulators in the presence of rat Con A supernatant and rIL-2. A standard 5-h 51Cr release assay with 3 x 103 targets/well was employed. When peptide was added, targets were incubated with synthetic peptides for 0.5 to 1 h before the addition of effector cells. In the case of experiments using SIYR-8, targets were extensively washed before the addition of effector cells to avoid presentation of SIYR-8 by T cells. The percent specific lysis was calculated as follows: [(experimental lysis - spontaneous lysis)/(maximum release - spontaneous lysis)] x 100.
Flow cytometric analysis by conformational sensitive Abs
T2-Kb/Ld cells (5–7 x
105) were incubated with 10 µM of the indicated peptide
at 37°C for 3 h. Cells were then washed and incubated with mAbs
in culture supernatant, except 100.3 and 5F1.2-14, which were ascites.
The mAb 28-14-8S (American Type Culture Collection, Rockville, MD) is
specific for the 
3 domain of the chimeric
Kb/Ld molecule and served as an indicator of
surface expression that was independent of peptide changes in the
1-2 regions. The mAbs used were K10.56 (19), 28-13-3 (American
Type Culture Collection), 100.3 (provided by K. Hogquist, University of
Minnesota, St. Paul, MN), and 5F1.2-14 (provided by P. Wettstein, Mayo
Clinic, Rochester, MN). Detection of Abs was performed with FITC-goat
anti-mouse IgG (Biosource International, Camarillo, CA). Flow
cytometry was performed on a FACScan (Becton Dickinson, Mountain View,
CA), and mean channel fluorescence
(MCF)4 values were obtained.
Correction of mean channel differences was calculated as follows:
corrected mean channel difference = MCF peptide-pulsed mAb -
MCF-unpulsed mAb + MCF peptide-pulsed 28-14-8 - MCF-unpulsed
28-14-8. The corrected value represents the change in conformation
after changes in levels of surface expression have been taken into
consideration.
RMA-S stabilization
RMA-S cells (2 x 105) were incubated at 26°C with the indicated concentrations of peptide for 7 h and then moved to 37°C for 3 h. Cells were then washed and stained for Kb expression with the primary Ab B8-24-3 (American Type Culture Collection) and an FITC-conjugated goat anti-mouse Fab' secondary Ab (Biosource International, Camarillo, CA).
Molecular modeling
Starting atomic coordinates for molecular modeling were obtained from three MHC class I H-2Kb structures in the Brookhaven Protein Data Bank with identification codes 1VAA (10), 1VAB (10), and 1VAC (11). The 1VAA structure complexed with an eight-residue vesicular stomatitis virus peptide (Kb:VSV-8) was mutated using the program O (20) to generate starting coordinates for both the H-2Kbm3+peptide structures (Kb:dEV-8, Kb:p2Ca, Kb:SIYR-8) and the H-2Kbm3+peptide structures (Kbm3:dEV-8, Kbm3:p2Ca, Kbm3:SIYR-8). In all cases, the most frequently occurring side chain rotamer in the O database (21) was selected as the starting side chain conformation for the mutated residues.
The starting coordinates for each system were then used in the program
X-PLOR 3.1 (22) for energy minimization and molecular dynamics.
Coordinates were modified in X-PLOR to remove residues 181 to 274 of
the A chain (3 domain), ß2m, and all
crystallographically defined water molecules not within 3 Å of
residues 1 to 180 (1 and 2 domains). The resulting system was
centered in a box of 60 Å x 40 Å x 60 Å with P1 symmetry. Polar
hydrogens were then added to the protein and peptide consistent with
the use of standard crystallographic force-field parameters (23) as
implemented within the X-PLOR program. To completely solvate the
system, additional water molecules were systematically added by
translation of a pre-equilibrated smaller box of 125 water molecules to
fill the simulation box excluding a region within 3 Å of the protein
surface. The final systems contained approximately 11,400 atoms,
including about 3,200 water molecules (9,600 atoms).
The X-PLOR-modified coordinates were subjected to 150 cycles of
Powell energy minimization followed by a molecular dynamics step and a
final 150 cycles of energy minimization. Molecular dynamics was
conducted using a simulated annealing protocol with an integration time
of 0.2 ps (400 0.5-fs steps) at each of 18 temperature steps of
-100°K between a starting temperature of 2000°K and a final
temperature of 300°K. All energy minimization and molecular dynamics
steps were conducted within X-PLOR using coordinate-based shake
constraints for protein and peptide hydrogens and parameter-based shake
constraints for water molecules (22). Additional mild harmonic
restraints were imposed on the A chain to compensate for removal of the
3 and ß2m domains, and, more importantly, to provide
realistic restraints to molecular motion consistent with the known
crystal structures. Averaged rmsd values for A chain residues were
calculated a priori using X-PLOR for pairwise least squares
superpositions of the three H-2Kb structures in the PDB
(1VAA, 1VAB, and 1VAC). The average rmsd was 0.181 Å for A chain
backbone atoms and 0.552 Å for A chain side chain atoms for these
three structures. For each simulation, a harmonic restraint coefficient
for a given A chain residue was set to the average backbone rmsd
(0.181) divided by the rmsd for backbone atoms of that residue, and
similarly to the average rmsd (0.552) divided by the rmsd for side
chain atoms of the residue. Examination of the molecular dynamics
trajectories showed that such restraints allowed more motion in protein
loops than in regions of well-defined secondary structure. Each
simulation required approximately 14 h of computational time on a
Silicon Graphics Indigo-2 R4400 (150 MHz) machine (Silicon Graphics,
Mountainview, CA).
Final coordinate sets obtained after simulated annealing and energy
minimization were compared using X-PLOR by least squares minimization
of protein backbone atom (N, CA, C, O) distances for residues 1 to 180
of the 1 and 2 domains. Peptide atoms and mutated residues
(positions 77 and 89) were not included in least squares
calculations.
After least squares superposition of paired coordinate sets, atomic displacements were calculated using a UNIX command file script devised for that purpose and then mapped to a molecular surface rendered with the program GRASP (24). Molecular surface displacement of superposed structures was calculated and displayed using GRASP. Atom-by-atom solvent-accessible surface areas were calculated in GRASP using a probe radius of 1.4 Å; difference calculations were made using a UNIX command file script and then displayed using GRASP. Electrostatic potential maps were calculated and displayed using GRASP, assuming a salt concentration of 0.1 M.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Recently, several antigenic peptides have been defined for the
alloreactive 2C TCR (see Table I
). To evaluate the level of degeneracy
of 2C recognition, we tested the panel of peptides in the context of
two class I molecules that are alloantigens for the 2C TCR and also in
the context of the self-restriction element for 2C, Kb
(see Table II and Fig. 1). As previously known, the
Ld allopeptide, p2Ca, was antigenic when presented to 2C
cells by Ld or Kb (9, 14, 25), but not by
Kbm3 (26). In the present analysis the Kbm3
allopeptide dEV-8 was recognized in the context of both Kb
and Kbm3, but not Ld. The peptide SIYR-8, which
has defined antigenicity when presented by the Kb molecule
(15), was not seen by 2C in our study when presented by
Ld-bearing cells (Table II), but was recognized when
presented by Kbm3 (Table III). Thus, the 2C TCR recognition of
peptide Ags was specific in the context of the alloantigens
Ld, but degenerate in the recognition of all three peptides
when presented by the self-restricting element, Kb. Other
peptides, such as mLBP, OVA-8, and a library of unrelated peptides
derived from known Kb binding peptides (27), were not
recognized by 2C, even when presented at a 5-µM concentration by
TAP-deficient APC. This (data not shown) indicates that there is a high
level of peptide specificity in 2C recognition of Kb.
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We next chose to compare the binding efficiency of each peptide
for the Kb molecule using an RMA-S stabilization assay
(Fig. 2). The antigenic SIYR-8 stabilized
the surface expression of Kb as efficiently as the strong
Kb-restricted peptide Ag OVA-8. The two more weakly
antigenic peptides, p2Ca and dEV-8, were less efficient at stabilizing
Kb in this assay. The nonantigenic peptide, mLBP,
stabilized Kb intermediately. Significantly, all peptides
were capable of binding and stabilizing Kb, a finding
consistent with ability of 2C to recognize three of the peptides when
presented by Kb. The inability of 2C cells to lyse targets
bearing the mLBP or OVA peptides is not due to the inability of the
peptides to bind the Ag-presenting molecule. The increased peptide
concentrations required for recognition of dEV-8 and p2Ca in
Kb appears to be related at least in part to lower peptide
binding affinities. However, judging from the similar quantities of
endogenous dEV-8 recoverable from immunoaffinity-purified
Kb and Kbm3 isolated from cells (26), the
quantitative differences in recognition of Kb:dEV-8 and
Kbm3:dEV-8 are not directly related to differences in
peptide:MHC binding.
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The differences in fine specificity in the recognition by 2C of
the peptides presented in the context of Kb or
Kbm3 led us to compare the surfaces of the MHC/peptide
complexes with conformation-sensitive Abs. These Abs bind
Kb differentially depending on the structure of the
peptides bound or as a consequence of amino acid substitutions on the
floor of the class I peptide binding site (28, 29). Consequently, Ab
can be used as a measurement of surface structure when a particular
peptide is bound. The Ab binding measurements were normalized by
subtracting the increase in surface epitope expression induced by
peptide addition, as determined by mAb 28-14-8, from the values
determined for binding of specific, conformationally dependent Abs. An
example of the fluorescence shift is illustrated in Figure 3. Only one Ab, 28-13-3, did not bind
Kbm3 as efficiently as it bound Kb when no
peptide was added (Table IV). Two
inferences can be made from these data. The first comes from directly
comparing the conformation-sensitive Ab binding across the panel of
peptides. Comparisons that revealed increases or decreases within 50
channels were judged to be similar. When bound to the Kb
molecule, dEV-8 and SIYR-8 induced conformations that were recognized
similarly by three of the four Abs (K10.56, 28-13-3, and 100.3). Only
5F1.2.14 was able to distinguish between the two bound peptides.
Peptide p2Ca, compared with SIYR-8 or dEV-8, had similar binding
profiles for two of the four Abs (K10.56 and 28-13-3). Both 5F1.2.14
and 100.3 differentially bound the p2Ca-Kb complex relative
to dEV8-Kb or SIYR-8-Kb. This suggests that the
structure of p2Ca in Kb is less similar to dEV-8 than is
the structure of SIYR-8. When looking at the effects of the binding of
other peptides on Ab epitopes expressed by Kb and
Kbm3, it was evident that there was a wide range of
conformational changes induced by the peptides, and that some peptides
had very dramatic influences on the conformational structure of the
class I molecules. For example, OVA altered the structures of three of
the four Abs substantially in the case of Kb and of all
four Abs in the case of Kbm3.
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further illustrates that the epitope profiles of
Kb and Kbm3 vary differentially as a
consequence of binding to a broader set of five peptides. This is
evident upon comparison of the relative magnitude and direction of
change in Ab binding when each of the five peptides is bound to
Kb or Kbm3 (compare the boldface values in
Table IV). No peptide generated the same profile when bound to
Kb and Kbm3. This leads to the conclusion that
a major consequence of the amino acid substitution at position 77 in
Kbm3 is to change the pattern of conformations of the
Ab-accessible surface in a peptide-dependent manner. The implication of
this finding is that the peptides may induce similar structural changes
at the molecular surface that influence TCR recognition. As all five
peptides induce different epitope profiles, it is reasonable to
consider the possibility that such differences are widespread among
both self and non-self peptides bound and presented to T cells by
Kb and Kbm3. However, it is important to point
out that these structural differences observed using mAbs do not
necessarily correlate with the binding patterns of specific TCR as 2C
recognizes SIYR-8 efficiently in the context of both Kb and
Kbm3 (more differences in Ab binding) and differentially
when dEV-8 is presented by both molecules (fewer mAb binding
differences). Similarly, the extensive Ab epitope differences (four of
four mAbs in Table IV) observed in the comparison of Kb-OVA
and Kbm3-OVA are reflected by the differential recognition
T cell lines to recognize OVA-pulsed Kbm3 target cells
(30). Molecular models of peptides
Because the primary sequences of these peptides do not provide direct information about the tertiary structure of the peptides when they are complexed with Kb, and no crystal structure of Kb is available with the three peptides of interest, we generated a model of each peptide in the Kb groove using a published crystal structures for the Kb:VSV-8 peptide complex (10) as a reference structure. The amino acid residues for the VSV peptide from the Kb:VSV-8 crystal structure were replaced with the corresponding residues of the three peptides, dEV-8, SIYR-8, and p2Ca. The modified structures were then subjected to energy minimization and molecular dynamics. The interactions with ß2m were not included in the simulation. However, restraints on the movement of atoms in the Kb heavy chain were introduced to simulate the contribution of ß2m and other unknown determinants of class I structure. We reasoned that important restraints would be reflected in conserved similarities between known structures of Kb as the molecule is bound to different peptides. Three such structures have been solved (10, 11). Imposed movement restraints for each atom were inversely proportional to the least squares rmsd deviation values calculated from the three sets of coordinates for the Kb crystals (see Materials and Methods). Similar models could not be conducted of Ld, as no structural coordinates have been reported.
The dEV-8 and SIYR-8 peptides exhibit similar predicted conformations in the Kb class I molecule
The predicted conformations of the dEV-8 and SIYR-8 peptides, both
antigenic in the context of Kb, are surprisingly
similar (Fig. 4A). The
positions of the peptide backbone atoms are nearly identical (rmsd
= 0.534 Å, compared with an rmsd of 0.657 Å for the unmodified
Kb:VSV-8 structure subjected to the same manipulations).
The aromatic side chain residues at P3, P5, and P6 have very similar,
overlapping conformations within the binding groove. Even the
positively charged side chain at P4 (Lys, dEV-8; Arg, SIYR-8) is
pointing up out of the groove in a similar manner. The remaining side
chains at P1, P2, P7, and P8 also have very similar conformations when
considering the differences between the residues. After comparing these
two peptides modeled into the Kb molecule, it is not
difficult to appreciate the fact that they are both seen similarly by
the 2C TCR and our panel of mAbs. Nonetheless, some of the modest
differences between the two peptides and interacting heavy chain
regions must contribute to the significant quantitative differences in
the ability of the 2C T cell to respond to the two different peptides
when bound to Kb.
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In contrast to the similarity of conformation of dEV-8 and SIYR-8,
is the dissimilarity of the p2Ca conformation (Fig. 4B). When p2Ca was modeled into the Kb
molecule, the positional changes in the peptide backbone atoms were
greater (rmsd = 0.798 Å). The first point to note is that p2Ca
does not have an aromatic residue positioned in pocket C. (Note the
proline ring at the center of p2Ca in place of the tyrosine ring that
projects down into pocket C.) This position is commonly a strong anchor
position for the Kb molecule (31). Another dramatic
difference between p2Ca and dEV-8 or SIYR-8 is the lack of Tyr at P3.
P3 is a proposed secondary anchor position that interacts with pocket D
(32). Despite these major differences, some minor similarities can be
observed between p2Ca conformation and the conformation of the other
two 2C antigenic peptides. As illustrated in Figure 4B, the
most obvious similarity is the aromatic residue at P6, which is in a
similar orientation to that seen for the analogous amino acid in
SIYR-8. The other shared feature, although not as striking, is the
amino acid residue at P4. This residue in both peptides is pointing
directly out of the groove in a position that would interact with the
TCR. Even though the PheP4 of p2Ca does not have the
similar charge or shape of dEV-8 (LysP4) or SIYR-8
(ArgP4), it does have the similar planar structure as the
ArgP4 in SIYR-8. Aside from these minimal similarities and
those at the N-terminus and C-terminus, the p2Ca peptide conformation
is very distinct from the SIYR-8 and dEV-8 conformations. Nonetheless,
the 2C T cell responds to Kb-expressing cells loaded with
p2Ca approximately as well as to cells loaded with dEV-8 (Fig. 1).
Structure of peptides when bound to Kbm3
We next sought to appreciate the structural significance of the
amino acid replacement at amino acids 77 (Asp to Ser) and 89 (Lys to
Ala) in the Kbm3 molecule as they interact with the
three peptides. To accomplish this, we remodeled the peptide/heavy
chain structures after introducing the bm3 amino acid replacements at
positions 77 and 89 in the class I heavy chain. The first insight
emanating from the analysis is that the amino acid replacement in the
heavy chain has little direct influence on the surface of the class I
molecule. As shown in the molecular surfaces of Figure 5, there is little perturbation in the
positions of surface atoms (Fig. 5A), overall surface
structure (Fig. 5B), or accessible surface (Fig. 5C) in the immediate vicinity of amino acid 77. There
is, however, some modification of surface electrostatic potential that
results from the substitution of the Asp at position 77 (Fig. 5D). This is mostly confined to the peptide binding
groove beneath the bound peptide, a finding that is consistent with the
differential binding of mAb 28-13-3 with peptide-deficient
Kb and Kbm3 molecules expressed on transfected
T2 cells (Table IV). This absence of significant surface perturbation
in the presence of bound peptide is consistent with our previously
reported finding that amino acid position 77 does not influence Ab
epitopes expressed on the surface of normal (TAP-proficient) cells
(17). The implication is that the consequences of the substitution are
indirect, mediated by interactions with bound peptide. Such indirect
conformation changes can only be visualized by Ab staining when a large
number of cell surface molecules are bound to a single peptide species,
as seen in the case of peptide-pulsed TAP-deficient T2 cells.
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A). The backbone
atoms of the peptide as well as the orientation of the side chains are
very similar to those seen when the peptide is bound to Kb.
The major difference appears to be the orientation of the aromatic ring
of the Tyr residue at position 6. This structural similarity is
reflected in the similar mAb binding patterns shown in Table IV. In
contrast, the Kbm3 Asp to Ser substitutions have a more
pronounced influence on the structure of the dEV-8 and p2Ca peptides
(Fig. 6, B and C). These increased
differences observed in the models are consistent with the differences
seen using Abs to probe the molecular surface of the molecules (Table IV). In the case of both dEV-8 and p2Ca bound to Kbm3, the
positions of the peptide backbone atoms are displaced significantly for
residues 6, 7, and 8, changing the positions of each of the associated
side chains.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Several interesting points can be drawn from this study. One of the most intriguing is the fact that the 2C TCR can recognize three different peptides in the context of the self-restricting element Kb, albeit with differing levels of efficiency. The peptide SIYR-8 was recognized strongly (15) (our unpublished observations), while dEV-8 and p2Ca were recognized only when presented at high concentration on TAP-deficient cells. It is not clear at this time whether the ability of the 2C TCR to recognize this set of three peptides is fortuitous, or whether the fact that the 2C TCR undergoes positive selection in the context of Kb is related to this reactivity pattern. In support of the latter view, 2C recognition of Ld and Kbm3 did not exhibit the broad range of reactivity.
Molecular modeling revealed surprisingly similar structures in the case of two of the peptides, dEV-8 and SIYR-8, when they are presented by Kb. This view is consistent with the cross-reactivity of the two antigenic structures. However, the structure of the third peptide, p2Ca, appears to be very dissimilar when modeled into the Kb peptide binding site. The conclusion that 2C recognizes distinct structures was reached similarly in a recent study that modeled Kb-SIYR-8 and Ld-p2Ca for comparison of their TCR interactive surfaces (35).
Recently, several laboratories have shown that T cells can recognize minimally homologous peptides in the same class II molecule (6, 7). The distinction between our work and these earlier studies is that they found degeneracy of T cell recognition on only one specific class II molecule, and peptides were identified by substitution analysis and/or subsequent database searches. Here, we have shown that two nonhomologous, endogenous peptides are recognized similarly by the same TCR. When either of the two allopeptides, p2Ca and dEV-8, are added to T2-Kb cells, the 2C T cells are induced to lyse the target cells. While this is true for Kb, the addition of p2Ca to Kbm3 or dEV-8 to Ld does not permit lysis of those targets. The fact that the structures of these two peptides presented in the context of Kb appears to be very different raises the possibility that the class I heavy chain itself may play an important role in the selection of receptors during development of the repertoire. In line with this view, we have recently demonstrated positive selection of 2C in the context of class I molecules expressed in the thymus of TAP-1-mice (manuscript in preparation).
Another point that emerges from these studies is that a single residue
change on the class I molecule can alter substantially the recognition
by a T cell. Kbm3 differs from the Kb molecule
by only two amino acids at positions 77 and 89, (Asp
Ser and
LysAla, respectively). Amino acid position 89 is located on a loop
and is not important for the recognition of Kbm3 by T
cells, including 2C (36). Therefore, position 77 is solely responsible
for the differential recognition of Kb and
Kbm3. While SIYR-8 is highly antigenic when presented by
either Kb or Kbm3, significant differences are
observed in the ability of Kb and Kbm3 to
present dEV-8 and p2Ca. A broader implication of these findings is that
peptides that bind structurally related, but distinct, class I
molecules induce different conformations, as visualized using mAb or
molecular modeling. All five peptides analyzed conformed to this rule.
This has far-reaching implications in regard to the positive selection
of the T cell repertoire that is mediated by the presentation of self
peptide in the thymus. A single amino acid substitution in an MHC
molecule could thereby influence a substantial portion of the
developing T cell repertoire, as the nature of TCR interactions with
these altered conformations could result in fine specificity
differences exemplified by dEV8 and p2Ca presentation by Kb
and Kbm3.
Two of the peptides analyzed in this study, p2Ca and dEV-8, are from endogenous sources and have the potential of playing a role in selection of the 2C TCR. While we observe strong recognition in the context of high density presentation of these peptides by TAP-deficient target cells, normal cells expressing these peptides are not highly antigenic. The apparent low affinity/avidity of these complexes for the 2C TCR is consistent with the selection model that proposes that moderate affinity/avidity situations allow positive selection (2, 36). Therefore, as suggested previously (5, 14, 25), p2Ca and/or dEV-8 may play a role in selecting the 2C TCR. However, despite extensive efforts to assess the role of either peptide in positive selection of 2C thymocytes using fetal thymic organ culture, we have not been able to demonstrate such a relationship. Another group has suggested that many different peptides, including p2Ca, QL-9, and OVA-8, promote positive selection of 2C in FTOC, while other Kb binding peptides do not (37). These results are consistent with the possibility that another, yet undefined peptide or set of endogenous peptides is responsible for the selection of the 2C TCR. However, conclusions along this line should be viewed cautiously because the in vitro FTOC system may not provide the conditions necessary for the appropriate development of every transgenic TCR-bearing cell. The development of in vivo techniques may supply the necessary approach to tackle this question.
The ability of a T cell to interact with a variety of ligands may be beneficial to the effective immune response. We have shown that the 2C TCR has the capability of associating with three different peptides in the context of its restriction element, Kb. While this degeneracy exists for recognition of peptides in Kb, this same peptide degeneracy is not observed for the two alloantigens that 2C also recognizes. The most interesting feature of the recognition on Kb is that dEV-8 and SIYR-8 (identified independently) are structurally similar, while p2Ca has little in common with the former two peptides, either structurally or conformationally. This system illustrates a connectivity between self and antigenic peptides, and it will be interesting to see whether this is a general principle in T cell recognition.
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Acknowledgments |
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Footnotes |
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2 Current address: Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109-1024.
3 Address correspondence and reprint requests to Dr. Larry R. Pease, Department of Immunology, Mayo Clinic/Foundation, 200 First St. SW, Rochester, MN 55905.
4 Abbreviations used in this paper: MCF, mean channel fluorescence; rmsd, root-mean-square displacement; mLBP, mouse LPS binding protein; VSV-8, eight-residue vesicular stomatitis virus peptide.
Received for publication February 19, 1997. Accepted for publication July 22, 1997.
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References |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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ß T cell receptor structure at 2.5 Å and its orientation in the TCR-MHC complex. Science 274:209.This article has been cited by other articles:
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  Q. Leng, Q. Ge, T. Nguyen, H. N. Eisen, and J. Chen Stage-dependent reactivity of thymocytes to self-peptide-MHC complexes PNAS, March 20, 2007; 104(12): 5038 - 5043. [Abstract] [Full Text] [PDF]
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 X.-Z. Yu, M. H. Albert, and C. Anasetti Alloantigen Affinity and CD4 Help Determine Severity of Graft-versus-Host Disease Mediated by CD8 Donor T Cells J. Immunol., March 15, 2006; 176(6): 3383 - 3390. [Abstract] [Full Text] [PDF]
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N. J. Felix, A. Suri, J. J. Walters, S. Horvath, M. L. Gross, and P. M. Allen I-Ep-Bound Self-Peptides: Identification, Characterization, and Role in Alloreactivity J. Immunol., January 15, 2006; 176(2): 1062 - 1071. [Abstract] [Full Text] [PDF]
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A. M. E. Whitelegg, L. E. M. Oosten, S. Jordan, M. Kester, A. G. S. van Halteren, J. A. Madrigal, E. Goulmy, and L. D. Barber Investigation of Peptide Involvement in T Cell Allorecognition Using Recombinant HLA Class I Multimers J. Immunol., August 1, 2005; 175(3): 1706 - 1714. [Abstract] [Full Text] [PDF]
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M. G. Rudolph, L. Q. Shen, S. A. Lamontagne, J. G. Luz, J. R. Delaney, Q. Ge, B. K. Cho, D. Palliser, C. A. McKinley, J. Chen, et al. A Peptide That Antagonizes TCR-Mediated Reactions with Both Syngeneic and Allogeneic Agonists: Functional and Structural Aspects J. Immunol., March 1, 2004; 172(5): 2994 - 3002. [Abstract] [Full Text] [PDF]
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Y. Y. L. Yu, N. Netuschil, L. Lybarger, J. M. Connolly, and T. H. Hansen Cutting Edge: Single-Chain Trimers of MHC Class I Molecules Form Stable Structures That Potently Stimulate Antigen-Specific T Cells and B Cells J. Immunol., April 1, 2002; 168(7): 3145 - 3149. [Abstract] [Full Text] [PDF]
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T. M. C. Hornell, S. M. Martin, N. B. Myers, and J. M. Connolly Peptide Length Variants p2Ca and QL9 Present Distinct Conformations to Ld-Specific T Cells J. Immunol., October 15, 2001; 167(8): 4207 - 4214. [Abstract] [Full Text] [PDF]
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M. M. Maurice, D. S. Gould, J. Carroll, Y. Vugmeyster, and H. L. Ploegh Positive selection of an MHC class-I restricted TCR in the absence of classical MHC class I molecules PNAS, June 7, 2001; (2001) 141143298. [Abstract] [Full Text] [PDF]
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 N. J. Felix, W. J. Brickey, R. Griffiths, J. Zhang, L. Van Kaer, T. Coffman, and J. P.-Y. Ting H2-DM{alpha}-/- Mice Show the Importance of Major Histocompatibility Complex-bound Peptide in Cardiac Allograft Rejection J. Exp. Med., June 26, 2000; 192(1): 31 - 40. [Abstract] [Full Text] [PDF]
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R. Obst, N. Netuschil, K. Klopfer, S. Stevanovi, and H.-G. Rammensee The Role of Peptides in T Cell Alloreactivity Is Determined by Self-Major Histocompatibility Complex Molecules J. Exp. Med., March 6, 2000; 191(5): 805 - 812. [Abstract] [Full Text] [PDF]
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S. T. Kuhns, M. D. Tallquist, A. J. Johnson, Y. Mendez-Fernandez, and L. R. Pease T cell receptor interactions with class I heavy-chain influence T cell selection PNAS, January 18, 2000; 97(2): 756 - 760. [Abstract] [Full Text] [PDF]
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M. Garcia-Peydro, A. Paradela, J. R. Lamas, and J. A. Lopez de Castro Peptide Presentation to an Alloreactive CTL Clone Is Modulated Through Multiple Mechanisms Involving Polymorphic and Conserved Residues in HLA-B27 J. Immunol., December 1, 1999; 163(11): 6060 - 6064. [Abstract] [Full Text] [PDF]
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T. M. C. Hornell, J. C. Solheim, N. B. Myers, W. E. Gillanders, G. K. Balendiran, T. H. Hansen, and J. M. Connolly Alloreactive and Syngeneic CTL Are Comparably Dependent on Interaction with MHC Class I {alpha}-Helical Residues J. Immunol., September 15, 1999; 163(6): 3217 - 3225. [Abstract] [Full Text] [PDF]
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R. Zhao, D. J. Loftus, E. Appella, and E. J. Collins Structural Evidence of T Cell Xeno-reactivity in the Absence of Molecular Mimicry J. Exp. Med., January 18, 1999; 189(2): 359 - 370. [Abstract] [Full Text] [PDF]
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 K. C. Garcia, M. Degano, L. R. Pease, M. Huang, P. A. Peterson, L. Teyton, and I. A. Wilson Structural Basis of Plasticity in T Cell Receptor Recognition of a Self Peptide-MHC Antigen Science, February 20, 1998; 279(5354): 1166 - 1172. [Abstract] [Full Text]
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M. M. Maurice, D. S. Gould, J. Carroll, Y. Vugmeyster, and H. L. Ploegh Positive selection of an MHC class-I restricted TCR in the absence of classical MHC class I molecules PNAS, June 19, 2001; 98(13): 7437 - 7442. [Abstract] [Full Text] [PDF]
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J. G. Luz, M. Huang, K. C. Garcia, M. G. Rudolph, V. Apostolopoulos, L. Teyton, and I. A. Wilson Structural Comparison of Allogeneic and Syngeneic T Cell Receptor-Peptide-Major Histocompatibility Complex Complexes: A Buried Alloreactive Mutation Subtly Alters Peptide Presentation Substantially Increasing V{beta} Interactions J. Exp. Med., May 6, 2002; 195(9): 1175 - 1186. [Abstract] [Full Text] [PDF]
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