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The efficiency of CD4 recruitment to ligand-engaged TCR controls the agonist/partial agonist properties of peptide-MHC molecule ligands.

Madrenas J, Chau LA, Smith J, Bluestone JA, Germain RN - J. Exp. Med. (1997)

Bottom Line: Likewise, antibody coligation of CD3 and CD4 results in an agonist-like phosphorylation pattern, whereas bivalent engagement of CD3 alone gives a partial agonist-like pattern.These results demonstrate that the biochemical and functional responses to variant TCR ligands with partial agonist properties can be largely reproduced by inhibiting recruitment of CD4 to a TCR binding a wild-type ligand, consistent with the idea that the relative rates of TCR-ligand disengagement and of association of engaged TCR with CD4 may play a key role in determining the pharmacologic properties of peptide-MHC molecule ligands.Beyond this insight into signaling through the TCR, these results have implications for models of thymocyte selection and the use of anti-coreceptor antibodies in vivo for the establishment ofimmunological tolerance.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology, The University of Western Ontario, London, Canada.

ABSTRACT
One hypothesis seeking to explain the signaling and biological properties of T cell receptor for antigen (TCR) partial agonists and antagonists is the coreceptor density/kinetic model, which proposes that the pharmacologic behavior of a TCR ligand is largely determined by the relative rates of (a) dissociation ofligand from an engaged TCR and (b) recruitment oflck-linked coreceptors to this ligand-engaged receptor. Using several approaches to prevent or reduce the association of CD4 with occupied TCR, we demonstrate that consistent with this hypothesis, the biological and biochemical consequence of limiting this interaction is to convert typical agonists into partial agonist stimuli. Thus, adding anti-CD4 antibody to T cells recognizing a wild-type peptide-MHC class II ligand leads to disproportionate inhibition of interleukin-2 (IL-2) relative to IL-3 production, the same pattern seen using a TCR partial agonist/antagonist. In addition, T cells exposed to wild-type ligand in the presence of anti-CD4 antibodies show a pattern of TCR signaling resembling that seen using partial agonists, with predominant accumulation of the p21 tyrosine-phosphorylated form of TCR-zeta, reduced tyrosine phosphorylation of CD3epsilon, and no detectable phosphorylation of ZAP-70. Similar results are obtained when the wild-type ligand is presented by mutant class II MHC molecules unable to bind CD4. Likewise, antibody coligation of CD3 and CD4 results in an agonist-like phosphorylation pattern, whereas bivalent engagement of CD3 alone gives a partial agonist-like pattern. Finally, in accord with data showing that partial agonists often induce T cell anergy, CD4 blockade during antigen exposure renders cloned T cells unable to produce IL-2 upon restimulation. These results demonstrate that the biochemical and functional responses to variant TCR ligands with partial agonist properties can be largely reproduced by inhibiting recruitment of CD4 to a TCR binding a wild-type ligand, consistent with the idea that the relative rates of TCR-ligand disengagement and of association of engaged TCR with CD4 may play a key role in determining the pharmacologic properties of peptide-MHC molecule ligands. Beyond this insight into signaling through the TCR, these results have implications for models of thymocyte selection and the use of anti-coreceptor antibodies in vivo for the establishment ofimmunological tolerance.

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TK.G4 T cell responses to cognate peptide bound to wildtype MHC class II molecules or to mutant MHC class II molecules unable to bind CD4. (a) Proliferative response of TK.G4 cells stimulated  with Swmyo(102–118) + wild-type I-Ad or Swmyo(102–118) + I-Ad  mutated at the primary CD4 binding site. (b) Tyrosine phosphorylation  analysis of cell lysates (top) and anti-CD3ε (bottom) immunoprecipitates  from TK.G4 cells stimulated under the same conditions.
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Figure 4: TK.G4 T cell responses to cognate peptide bound to wildtype MHC class II molecules or to mutant MHC class II molecules unable to bind CD4. (a) Proliferative response of TK.G4 cells stimulated with Swmyo(102–118) + wild-type I-Ad or Swmyo(102–118) + I-Ad mutated at the primary CD4 binding site. (b) Tyrosine phosphorylation analysis of cell lysates (top) and anti-CD3ε (bottom) immunoprecipitates from TK.G4 cells stimulated under the same conditions.

Mentions: To examine whether the lack of CD4 recruitment to the TCR leads to a partial agonist pattern of response under conditions not involving antibody ligation of CD4, we examined the functional and biochemical responses of a CD4+ T cell clone to its specific peptide presented by either wild-type class II molecules or by class II molecules in which the main CD4 binding site has been mutated (36, 42, 43). TK.G4 is a Th1 clone specific for sperm whale myoglobin fragment 102–118 (SWmyo[102–118]) bound to I-Ad molecules. The proliferative response of TK.G4 to this peptide–MHC class II molecule combination is CD4 dependent as shown by a significant reduction in the magnitude of the response when CD4 cannot bind to the I-Ad molecule present on the APC (Fig. 4 a). Under these conditions involving presentation of antigen by a mutant class II molecule, a pattern of signaling similar to that typical of partial agonist stimulation is observed (Fig. 4 b). This cannot be simply attributed to lower overall signaling from the TCR because pp21 TCR-ζ reaches a higher level under these conditions than when the same clone is stimulated with 10 μM SWmyo(102–118) and wild type I-Ad, yet the latter produces a higher proliferative response and shows substantial pp23 TCR-ζ accumulation not seen with the mutant class II ligand (data not shown).


The efficiency of CD4 recruitment to ligand-engaged TCR controls the agonist/partial agonist properties of peptide-MHC molecule ligands.

Madrenas J, Chau LA, Smith J, Bluestone JA, Germain RN - J. Exp. Med. (1997)

TK.G4 T cell responses to cognate peptide bound to wildtype MHC class II molecules or to mutant MHC class II molecules unable to bind CD4. (a) Proliferative response of TK.G4 cells stimulated  with Swmyo(102–118) + wild-type I-Ad or Swmyo(102–118) + I-Ad  mutated at the primary CD4 binding site. (b) Tyrosine phosphorylation  analysis of cell lysates (top) and anti-CD3ε (bottom) immunoprecipitates  from TK.G4 cells stimulated under the same conditions.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2196122&req=5

Figure 4: TK.G4 T cell responses to cognate peptide bound to wildtype MHC class II molecules or to mutant MHC class II molecules unable to bind CD4. (a) Proliferative response of TK.G4 cells stimulated with Swmyo(102–118) + wild-type I-Ad or Swmyo(102–118) + I-Ad mutated at the primary CD4 binding site. (b) Tyrosine phosphorylation analysis of cell lysates (top) and anti-CD3ε (bottom) immunoprecipitates from TK.G4 cells stimulated under the same conditions.
Mentions: To examine whether the lack of CD4 recruitment to the TCR leads to a partial agonist pattern of response under conditions not involving antibody ligation of CD4, we examined the functional and biochemical responses of a CD4+ T cell clone to its specific peptide presented by either wild-type class II molecules or by class II molecules in which the main CD4 binding site has been mutated (36, 42, 43). TK.G4 is a Th1 clone specific for sperm whale myoglobin fragment 102–118 (SWmyo[102–118]) bound to I-Ad molecules. The proliferative response of TK.G4 to this peptide–MHC class II molecule combination is CD4 dependent as shown by a significant reduction in the magnitude of the response when CD4 cannot bind to the I-Ad molecule present on the APC (Fig. 4 a). Under these conditions involving presentation of antigen by a mutant class II molecule, a pattern of signaling similar to that typical of partial agonist stimulation is observed (Fig. 4 b). This cannot be simply attributed to lower overall signaling from the TCR because pp21 TCR-ζ reaches a higher level under these conditions than when the same clone is stimulated with 10 μM SWmyo(102–118) and wild type I-Ad, yet the latter produces a higher proliferative response and shows substantial pp23 TCR-ζ accumulation not seen with the mutant class II ligand (data not shown).

Bottom Line: Likewise, antibody coligation of CD3 and CD4 results in an agonist-like phosphorylation pattern, whereas bivalent engagement of CD3 alone gives a partial agonist-like pattern.These results demonstrate that the biochemical and functional responses to variant TCR ligands with partial agonist properties can be largely reproduced by inhibiting recruitment of CD4 to a TCR binding a wild-type ligand, consistent with the idea that the relative rates of TCR-ligand disengagement and of association of engaged TCR with CD4 may play a key role in determining the pharmacologic properties of peptide-MHC molecule ligands.Beyond this insight into signaling through the TCR, these results have implications for models of thymocyte selection and the use of anti-coreceptor antibodies in vivo for the establishment ofimmunological tolerance.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology, The University of Western Ontario, London, Canada.

ABSTRACT
One hypothesis seeking to explain the signaling and biological properties of T cell receptor for antigen (TCR) partial agonists and antagonists is the coreceptor density/kinetic model, which proposes that the pharmacologic behavior of a TCR ligand is largely determined by the relative rates of (a) dissociation ofligand from an engaged TCR and (b) recruitment oflck-linked coreceptors to this ligand-engaged receptor. Using several approaches to prevent or reduce the association of CD4 with occupied TCR, we demonstrate that consistent with this hypothesis, the biological and biochemical consequence of limiting this interaction is to convert typical agonists into partial agonist stimuli. Thus, adding anti-CD4 antibody to T cells recognizing a wild-type peptide-MHC class II ligand leads to disproportionate inhibition of interleukin-2 (IL-2) relative to IL-3 production, the same pattern seen using a TCR partial agonist/antagonist. In addition, T cells exposed to wild-type ligand in the presence of anti-CD4 antibodies show a pattern of TCR signaling resembling that seen using partial agonists, with predominant accumulation of the p21 tyrosine-phosphorylated form of TCR-zeta, reduced tyrosine phosphorylation of CD3epsilon, and no detectable phosphorylation of ZAP-70. Similar results are obtained when the wild-type ligand is presented by mutant class II MHC molecules unable to bind CD4. Likewise, antibody coligation of CD3 and CD4 results in an agonist-like phosphorylation pattern, whereas bivalent engagement of CD3 alone gives a partial agonist-like pattern. Finally, in accord with data showing that partial agonists often induce T cell anergy, CD4 blockade during antigen exposure renders cloned T cells unable to produce IL-2 upon restimulation. These results demonstrate that the biochemical and functional responses to variant TCR ligands with partial agonist properties can be largely reproduced by inhibiting recruitment of CD4 to a TCR binding a wild-type ligand, consistent with the idea that the relative rates of TCR-ligand disengagement and of association of engaged TCR with CD4 may play a key role in determining the pharmacologic properties of peptide-MHC molecule ligands. Beyond this insight into signaling through the TCR, these results have implications for models of thymocyte selection and the use of anti-coreceptor antibodies in vivo for the establishment ofimmunological tolerance.

Show MeSH
Related in: MedlinePlus