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Altered hapten ligands antagonize trinitrophenyl-specific cytotoxic T cells and block internalization of hapten-specific receptors.

Preckel T, Grimm R, Martin S, Weltzien HU - J. Exp. Med. (1997)

Bottom Line: Our previous work provided evidence that hapten-specific T cells, in analogy to those specific for nominal peptide antigens, direct their TCR towards hapten-modified, MHC-associated peptides.No signs of anergy or functional receptor inactivation were observed in CTL treated with antagonist-loaded target cells.Based on a serial triggering model of T cell activation, our data favor a model in which antagonists block T cell functions by competitively engaging the specific TCR in unproductive interactions.

View Article: PubMed Central - PubMed

Affiliation: Max-Planck-Institut für Immunbiologie, Stübeweg 51, D-79108 Freiburg, Germany.

ABSTRACT
Low molecular chemicals (haptens) frequently cause T cell-mediated adverse immune reactions. Our previous work provided evidence that hapten-specific T cells, in analogy to those specific for nominal peptide antigens, direct their TCR towards hapten-modified, MHC-associated peptides. We now demonstrate that trinitrophenyl (TNP)-specific, class I MHC-restricted CTL from mice may exhibit exquisite specificity for subtle structural details of these hapten determinants, surpassing even the specificity of immunoglobulins. More importantly, these CTL could be antagonized by ligands altered either in their peptide sequence or in their hapten structure. The system was employed to examine the molecular basis of T cell antagonism. Whereas agonists resulted in a dose-dependent downregulation of TCR in different mouse T cell clones, antagonistic peptides totally failed to do so despite engaging the specific TCR. Moreover, simultaneous presentation of antagonist and agonist on the same antigen presenting cell prevented TCR internalization. No signs of anergy or functional receptor inactivation were observed in CTL treated with antagonist-loaded target cells. Based on a serial triggering model of T cell activation, our data favor a model in which antagonists block T cell functions by competitively engaging the specific TCR in unproductive interactions.

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Cold target inhibition of TNP-specific lysis by clone E8. Hot  RMA targets (labeled with Na251CrO4) were pulsed during labeling with  1 μM agonist O7TNP. Unlabeled (cold) targets were either untreated or  pulsed for 2.5 h with 200 μM of the indicated peptides. Targets were  mixed at a cold/hot ratio of 60:1 (5,000 hot targets per round-bottom  microtiter well), and CTL (clone E8) were added at an effector/hot target  ratio of 3:1. Chromium release was determined as described in Materials  and Methods. Lysis inhibition was calculated from maximal lysis in the  presence of untreated cold targets (52% specific lysis, corresponding to 0%  inhibition). Background lysis of hot targets in the absence of peptides or  cold targets was below 2%. Data represent mean of triplicates with SD indicated.
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Figure 6: Cold target inhibition of TNP-specific lysis by clone E8. Hot RMA targets (labeled with Na251CrO4) were pulsed during labeling with 1 μM agonist O7TNP. Unlabeled (cold) targets were either untreated or pulsed for 2.5 h with 200 μM of the indicated peptides. Targets were mixed at a cold/hot ratio of 60:1 (5,000 hot targets per round-bottom microtiter well), and CTL (clone E8) were added at an effector/hot target ratio of 3:1. Chromium release was determined as described in Materials and Methods. Lysis inhibition was calculated from maximal lysis in the presence of untreated cold targets (52% specific lysis, corresponding to 0% inhibition). Background lysis of hot targets in the absence of peptides or cold targets was below 2%. Data represent mean of triplicates with SD indicated.

Mentions: To test for a possible engagement of TCR with antagonistic peptide–Kb complexes we employed cold target competition assays. Nonradioactive (cold) RMA targets loaded with various peptides were mixed with 51Cr-labeled (hot), 07TNP-pulsed targets and subjected to lysis by clone E8. As seen in Fig. 6, cold targets presenting either the agonist 07TNP or the antagonist 07DNP resulted in comparative inhibition of lysis. In contrast, targets pulsed with the irrelevant peptide 07(N4R) were indistinguishable from RMA cells without added peptide. Hence, the antagonistic epitope clearly interacts with the antagonized TCR. However, this epitope not only fails to initiate the relevant TCR signals for lysis and proliferation, but it even blocks their induction by TCR–antigen contacts with the correct determinants presented on the same cell.


Altered hapten ligands antagonize trinitrophenyl-specific cytotoxic T cells and block internalization of hapten-specific receptors.

Preckel T, Grimm R, Martin S, Weltzien HU - J. Exp. Med. (1997)

Cold target inhibition of TNP-specific lysis by clone E8. Hot  RMA targets (labeled with Na251CrO4) were pulsed during labeling with  1 μM agonist O7TNP. Unlabeled (cold) targets were either untreated or  pulsed for 2.5 h with 200 μM of the indicated peptides. Targets were  mixed at a cold/hot ratio of 60:1 (5,000 hot targets per round-bottom  microtiter well), and CTL (clone E8) were added at an effector/hot target  ratio of 3:1. Chromium release was determined as described in Materials  and Methods. Lysis inhibition was calculated from maximal lysis in the  presence of untreated cold targets (52% specific lysis, corresponding to 0%  inhibition). Background lysis of hot targets in the absence of peptides or  cold targets was below 2%. Data represent mean of triplicates with SD indicated.
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Related In: Results  -  Collection

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Figure 6: Cold target inhibition of TNP-specific lysis by clone E8. Hot RMA targets (labeled with Na251CrO4) were pulsed during labeling with 1 μM agonist O7TNP. Unlabeled (cold) targets were either untreated or pulsed for 2.5 h with 200 μM of the indicated peptides. Targets were mixed at a cold/hot ratio of 60:1 (5,000 hot targets per round-bottom microtiter well), and CTL (clone E8) were added at an effector/hot target ratio of 3:1. Chromium release was determined as described in Materials and Methods. Lysis inhibition was calculated from maximal lysis in the presence of untreated cold targets (52% specific lysis, corresponding to 0% inhibition). Background lysis of hot targets in the absence of peptides or cold targets was below 2%. Data represent mean of triplicates with SD indicated.
Mentions: To test for a possible engagement of TCR with antagonistic peptide–Kb complexes we employed cold target competition assays. Nonradioactive (cold) RMA targets loaded with various peptides were mixed with 51Cr-labeled (hot), 07TNP-pulsed targets and subjected to lysis by clone E8. As seen in Fig. 6, cold targets presenting either the agonist 07TNP or the antagonist 07DNP resulted in comparative inhibition of lysis. In contrast, targets pulsed with the irrelevant peptide 07(N4R) were indistinguishable from RMA cells without added peptide. Hence, the antagonistic epitope clearly interacts with the antagonized TCR. However, this epitope not only fails to initiate the relevant TCR signals for lysis and proliferation, but it even blocks their induction by TCR–antigen contacts with the correct determinants presented on the same cell.

Bottom Line: Our previous work provided evidence that hapten-specific T cells, in analogy to those specific for nominal peptide antigens, direct their TCR towards hapten-modified, MHC-associated peptides.No signs of anergy or functional receptor inactivation were observed in CTL treated with antagonist-loaded target cells.Based on a serial triggering model of T cell activation, our data favor a model in which antagonists block T cell functions by competitively engaging the specific TCR in unproductive interactions.

View Article: PubMed Central - PubMed

Affiliation: Max-Planck-Institut für Immunbiologie, Stübeweg 51, D-79108 Freiburg, Germany.

ABSTRACT
Low molecular chemicals (haptens) frequently cause T cell-mediated adverse immune reactions. Our previous work provided evidence that hapten-specific T cells, in analogy to those specific for nominal peptide antigens, direct their TCR towards hapten-modified, MHC-associated peptides. We now demonstrate that trinitrophenyl (TNP)-specific, class I MHC-restricted CTL from mice may exhibit exquisite specificity for subtle structural details of these hapten determinants, surpassing even the specificity of immunoglobulins. More importantly, these CTL could be antagonized by ligands altered either in their peptide sequence or in their hapten structure. The system was employed to examine the molecular basis of T cell antagonism. Whereas agonists resulted in a dose-dependent downregulation of TCR in different mouse T cell clones, antagonistic peptides totally failed to do so despite engaging the specific TCR. Moreover, simultaneous presentation of antagonist and agonist on the same antigen presenting cell prevented TCR internalization. No signs of anergy or functional receptor inactivation were observed in CTL treated with antagonist-loaded target cells. Based on a serial triggering model of T cell activation, our data favor a model in which antagonists block T cell functions by competitively engaging the specific TCR in unproductive interactions.

Show MeSH
Related in: MedlinePlus