Limits...
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.

Show MeSH

Related in: MedlinePlus

Anergy induction by stimulation with wild-type ligand in  the presence of anti-CD4 antibody. (a) A.E7 T cells were incubated with  I-Ek-expressing L cells without or with PCC(81–104) (100 nM) and antiCD4 mAb (1:200 dilution of supernatant) for 24 h. T cells were then  isolated and rested for 7 d. At this point, T cells were restimulated with  I-Ek-transfected L cells and PCC(81–104) (1 μM) for 24 h and IL-2 production was measured by ELISA. (b) Effect of variation in the concentration of anti-CD4 mAb in the primary culture on the extent of anergy induction. A. E7 cells were treated as in (a), but using various concentrations  of anti-CD4 antibody (1:200, open squares; 1:2,000, closed diamonds;  1:20,000, half-filled squares; 1:200,000, half-filled diamonds; no antiCD4, closed triangles). After rest, each of these cell populations was restimulated as in (a) and IL-2 in the medium measured after 24 h by  ELISA.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2196122&req=5

Figure 6: Anergy induction by stimulation with wild-type ligand in the presence of anti-CD4 antibody. (a) A.E7 T cells were incubated with I-Ek-expressing L cells without or with PCC(81–104) (100 nM) and antiCD4 mAb (1:200 dilution of supernatant) for 24 h. T cells were then isolated and rested for 7 d. At this point, T cells were restimulated with I-Ek-transfected L cells and PCC(81–104) (1 μM) for 24 h and IL-2 production was measured by ELISA. (b) Effect of variation in the concentration of anti-CD4 mAb in the primary culture on the extent of anergy induction. A. E7 cells were treated as in (a), but using various concentrations of anti-CD4 antibody (1:200, open squares; 1:2,000, closed diamonds; 1:20,000, half-filled squares; 1:200,000, half-filled diamonds; no antiCD4, closed triangles). After rest, each of these cell populations was restimulated as in (a) and IL-2 in the medium measured after 24 h by ELISA.

Mentions: Recently, it has been shown that some partial agonists preferentially induce T cell clonal anergy rather than cytokine secretory activity even when presented by live APC able to provide costimulatory function due to expression of CD80/CD86 (1, 10, 44). The ability of these variant TCR ligands to induce anergy appeared to correlate with their ability to induce an altered pattern of TCR signaling (1). However, our own studies have indicated that the controlling factor in anergy induction is not the pattern of early phosphorylation itself, but the combination of a certain level of TCR signaling in the face of inadequate production of IL-2 due to either agonist exposure without costimulation, or partial agonist exposure even with costimulation (10). The ability of anti-CD4 to selectively inhibit IL-2 production while permitting substantial TCR signaling of the variant pattern suggested that anergy induction might accompany TCR engagement by agonist ligand on costimulatory APC in the face of antiCD4 blockade. This hypothesis would explain published findings showing that coadministration of nondepleting anti-CD4 mAb and antigen can induce a state of antigenspecific tolerance (45, 46). To investigate this possibility, A.E7 cells exposed to PCC(88–104) on I-Ek expressing, ICAM-1+, CD80+ L cells in the presence of anti-CD4 mAb were recovered after 24 h, rested for 7 d, and restimulated by agonist in the absence of anti-CD4. As shown in Fig. 6 A, the presence of anti-CD4 mAbs in the primary challenge of A.E7 T cells with antigenic peptide renders these cells less able to produce IL-2 in a subsequent rechallenge with the same antigenic peptide in the absence of the blocking antibody. The effectiveness of anergy induction by CD4 blockade correlates with the amount of anti-CD4 mAb present in the primary culture (Fig. 6 b). These results further confirm that CD4 blockade mimics the functional effects of TCR partial agonists and also provides a possible explanation for the induction of tolerance using anti-CD4 antibody in vivo.


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)

Anergy induction by stimulation with wild-type ligand in  the presence of anti-CD4 antibody. (a) A.E7 T cells were incubated with  I-Ek-expressing L cells without or with PCC(81–104) (100 nM) and antiCD4 mAb (1:200 dilution of supernatant) for 24 h. T cells were then  isolated and rested for 7 d. At this point, T cells were restimulated with  I-Ek-transfected L cells and PCC(81–104) (1 μM) for 24 h and IL-2 production was measured by ELISA. (b) Effect of variation in the concentration of anti-CD4 mAb in the primary culture on the extent of anergy induction. A. E7 cells were treated as in (a), but using various concentrations  of anti-CD4 antibody (1:200, open squares; 1:2,000, closed diamonds;  1:20,000, half-filled squares; 1:200,000, half-filled diamonds; no antiCD4, closed triangles). After rest, each of these cell populations was restimulated as in (a) and IL-2 in the medium measured after 24 h by  ELISA.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 6: Anergy induction by stimulation with wild-type ligand in the presence of anti-CD4 antibody. (a) A.E7 T cells were incubated with I-Ek-expressing L cells without or with PCC(81–104) (100 nM) and antiCD4 mAb (1:200 dilution of supernatant) for 24 h. T cells were then isolated and rested for 7 d. At this point, T cells were restimulated with I-Ek-transfected L cells and PCC(81–104) (1 μM) for 24 h and IL-2 production was measured by ELISA. (b) Effect of variation in the concentration of anti-CD4 mAb in the primary culture on the extent of anergy induction. A. E7 cells were treated as in (a), but using various concentrations of anti-CD4 antibody (1:200, open squares; 1:2,000, closed diamonds; 1:20,000, half-filled squares; 1:200,000, half-filled diamonds; no antiCD4, closed triangles). After rest, each of these cell populations was restimulated as in (a) and IL-2 in the medium measured after 24 h by ELISA.
Mentions: Recently, it has been shown that some partial agonists preferentially induce T cell clonal anergy rather than cytokine secretory activity even when presented by live APC able to provide costimulatory function due to expression of CD80/CD86 (1, 10, 44). The ability of these variant TCR ligands to induce anergy appeared to correlate with their ability to induce an altered pattern of TCR signaling (1). However, our own studies have indicated that the controlling factor in anergy induction is not the pattern of early phosphorylation itself, but the combination of a certain level of TCR signaling in the face of inadequate production of IL-2 due to either agonist exposure without costimulation, or partial agonist exposure even with costimulation (10). The ability of anti-CD4 to selectively inhibit IL-2 production while permitting substantial TCR signaling of the variant pattern suggested that anergy induction might accompany TCR engagement by agonist ligand on costimulatory APC in the face of antiCD4 blockade. This hypothesis would explain published findings showing that coadministration of nondepleting anti-CD4 mAb and antigen can induce a state of antigenspecific tolerance (45, 46). To investigate this possibility, A.E7 cells exposed to PCC(88–104) on I-Ek expressing, ICAM-1+, CD80+ L cells in the presence of anti-CD4 mAb were recovered after 24 h, rested for 7 d, and restimulated by agonist in the absence of anti-CD4. As shown in Fig. 6 A, the presence of anti-CD4 mAbs in the primary challenge of A.E7 T cells with antigenic peptide renders these cells less able to produce IL-2 in a subsequent rechallenge with the same antigenic peptide in the absence of the blocking antibody. The effectiveness of anergy induction by CD4 blockade correlates with the amount of anti-CD4 mAb present in the primary culture (Fig. 6 b). These results further confirm that CD4 blockade mimics the functional effects of TCR partial agonists and also provides a possible explanation for the induction of tolerance using anti-CD4 antibody in vivo.

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