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Costimulation by B7 modulates specificity of cytotoxic T lymphocytes: a missing link that explains some bystander T cell activation.

Zheng P, Liu Y - J. Exp. Med. (1997)

Bottom Line: However, this hypothesis is not supported by direct evidence since no TCR ligand is known to induce T cell proliferation and differentiation without being recognized by the effector CTL.Our results revealed that this is the case.These data demonstrated that costimulatory molecule B7 modulates antigen specificity of CTLs, and provides a missing link that explains some of the bystander T cell activation.

View Article: PubMed Central - PubMed

Affiliation: Michael Heidelberger Division of Immunology, Department of Pathology, New York University Medical Center 10016, USA.

ABSTRACT
It has been proposed that some bystander T cell activation may in fact be due to T cell antigen receptor (TCR) cross-reactivity that is too low to be detected by the effector cytotoxic T lymphocyte (CTL). However, this hypothesis is not supported by direct evidence since no TCR ligand is known to induce T cell proliferation and differentiation without being recognized by the effector CTL. Here we report that transgenic T cells expressing a T cell receptor to influenza virus A/NT/68 nucleoprotein (NP) 366-374:Db complexes clonally expand and become effector CTLs in response to homologous peptides from either A/PR8/34 (H1N1), A/AA/60 (H2N2), or A/NT/68 (H3N2). However, the effector T cells induced by each of the three peptides kill target cells pulsed with NP peptides from the H3N2 and H2N2 viruses, but not from the H1N1 virus. Thus, NP366-374 from influenza virus H1N1 is the first TCR ligand that can induce T cell proliferation and differentiation without being recognized by CTLs. Since induction of T cell proliferation was mediated by antigen-presenting cells that express costimulatory molecules such as B7, we investigated if cytolysis of H1N1 NP peptide-pulsed targets can be restored by expressing B7-1 on the target cells. Our results revealed that this is the case. These data demonstrated that costimulatory molecule B7 modulates antigen specificity of CTLs, and provides a missing link that explains some of the bystander T cell activation.

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Relative Db-binding  activity of the viral peptides used  for the study as determined by  MHC stabilization assay using  RMA-S cells. RMA-S cells  (105/well) were incubated overnight with varying concentrations of viral peptides in RPMI  medium containing 20% FCS.  The cell surfaces of H-2Db were  determined by flow cytometry  using biotinylated anti-Db mAb  (KH95) and PE-labeled streptavidin. Data presented are mean fluorescences, as measured by flow cytometry. The dotted line indicates expression of Db in the absence of exogenous peptide.
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Figure 2: Relative Db-binding activity of the viral peptides used for the study as determined by MHC stabilization assay using RMA-S cells. RMA-S cells (105/well) were incubated overnight with varying concentrations of viral peptides in RPMI medium containing 20% FCS. The cell surfaces of H-2Db were determined by flow cytometry using biotinylated anti-Db mAb (KH95) and PE-labeled streptavidin. Data presented are mean fluorescences, as measured by flow cytometry. The dotted line indicates expression of Db in the absence of exogenous peptide.

Mentions: The difference in the ability of the three peptides to induce F5 T cell proliferation and sensitize target cell lysis by CTL may be due either to the differential ability of these peptides to bind H-2Db, or to differential recognition of these peptides by the F5 TCR. We performed RMA-S Db-stabilization experiments to differentiate these possibilities. RMA-S cells lack functional TAP(transporter associated with antigen processing)-2 gene, and express empty MHC class I that can be stabilized by adding exogenous peptides (18). MHC stabilization assay has been widely used to measure MHC–peptide interaction on live cells. As shown in Fig. 2, NP peptides from H1N1 and H2N2 viruses are comparable in stabilizing H-2Db, whereas the peptide from H3N2 virus is ∼100-fold less efficient. Thus, the difference between the H3N2 and H2N2 NP peptides at position 8 affects their ability to bind Db, whereas the difference between the H1N1 and two other NP peptides at position 7 affects F5 TCR recognition. This is consistent with the three-dimensional structure of Db:NP peptide complex (19) in which the main chain and part of the side chain of the H1N1 peptide at position 8 are buried in the MHC, and residue E at position 7 is fully accessible to solvent. It is therefore likely that the unique split T cell response to the H1N1 NP peptide is caused by TCR ligand structure rather than ligand density.


Costimulation by B7 modulates specificity of cytotoxic T lymphocytes: a missing link that explains some bystander T cell activation.

Zheng P, Liu Y - J. Exp. Med. (1997)

Relative Db-binding  activity of the viral peptides used  for the study as determined by  MHC stabilization assay using  RMA-S cells. RMA-S cells  (105/well) were incubated overnight with varying concentrations of viral peptides in RPMI  medium containing 20% FCS.  The cell surfaces of H-2Db were  determined by flow cytometry  using biotinylated anti-Db mAb  (KH95) and PE-labeled streptavidin. Data presented are mean fluorescences, as measured by flow cytometry. The dotted line indicates expression of Db in the absence of exogenous peptide.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2199130&req=5

Figure 2: Relative Db-binding activity of the viral peptides used for the study as determined by MHC stabilization assay using RMA-S cells. RMA-S cells (105/well) were incubated overnight with varying concentrations of viral peptides in RPMI medium containing 20% FCS. The cell surfaces of H-2Db were determined by flow cytometry using biotinylated anti-Db mAb (KH95) and PE-labeled streptavidin. Data presented are mean fluorescences, as measured by flow cytometry. The dotted line indicates expression of Db in the absence of exogenous peptide.
Mentions: The difference in the ability of the three peptides to induce F5 T cell proliferation and sensitize target cell lysis by CTL may be due either to the differential ability of these peptides to bind H-2Db, or to differential recognition of these peptides by the F5 TCR. We performed RMA-S Db-stabilization experiments to differentiate these possibilities. RMA-S cells lack functional TAP(transporter associated with antigen processing)-2 gene, and express empty MHC class I that can be stabilized by adding exogenous peptides (18). MHC stabilization assay has been widely used to measure MHC–peptide interaction on live cells. As shown in Fig. 2, NP peptides from H1N1 and H2N2 viruses are comparable in stabilizing H-2Db, whereas the peptide from H3N2 virus is ∼100-fold less efficient. Thus, the difference between the H3N2 and H2N2 NP peptides at position 8 affects their ability to bind Db, whereas the difference between the H1N1 and two other NP peptides at position 7 affects F5 TCR recognition. This is consistent with the three-dimensional structure of Db:NP peptide complex (19) in which the main chain and part of the side chain of the H1N1 peptide at position 8 are buried in the MHC, and residue E at position 7 is fully accessible to solvent. It is therefore likely that the unique split T cell response to the H1N1 NP peptide is caused by TCR ligand structure rather than ligand density.

Bottom Line: However, this hypothesis is not supported by direct evidence since no TCR ligand is known to induce T cell proliferation and differentiation without being recognized by the effector CTL.Our results revealed that this is the case.These data demonstrated that costimulatory molecule B7 modulates antigen specificity of CTLs, and provides a missing link that explains some of the bystander T cell activation.

View Article: PubMed Central - PubMed

Affiliation: Michael Heidelberger Division of Immunology, Department of Pathology, New York University Medical Center 10016, USA.

ABSTRACT
It has been proposed that some bystander T cell activation may in fact be due to T cell antigen receptor (TCR) cross-reactivity that is too low to be detected by the effector cytotoxic T lymphocyte (CTL). However, this hypothesis is not supported by direct evidence since no TCR ligand is known to induce T cell proliferation and differentiation without being recognized by the effector CTL. Here we report that transgenic T cells expressing a T cell receptor to influenza virus A/NT/68 nucleoprotein (NP) 366-374:Db complexes clonally expand and become effector CTLs in response to homologous peptides from either A/PR8/34 (H1N1), A/AA/60 (H2N2), or A/NT/68 (H3N2). However, the effector T cells induced by each of the three peptides kill target cells pulsed with NP peptides from the H3N2 and H2N2 viruses, but not from the H1N1 virus. Thus, NP366-374 from influenza virus H1N1 is the first TCR ligand that can induce T cell proliferation and differentiation without being recognized by CTLs. Since induction of T cell proliferation was mediated by antigen-presenting cells that express costimulatory molecules such as B7, we investigated if cytolysis of H1N1 NP peptide-pulsed targets can be restored by expressing B7-1 on the target cells. Our results revealed that this is the case. These data demonstrated that costimulatory molecule B7 modulates antigen specificity of CTLs, and provides a missing link that explains some of the bystander T cell activation.

Show MeSH
Related in: MedlinePlus