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Requirements for peptide-induced T cell receptor downregulation on naive CD8+ T cells.

Cai Z, Kishimoto H, Brunmark A, Jackson MR, Peterson PA, Sprent J - J. Exp. Med. (1997)

Bottom Line: These stringent requirements did not apply to TCR downregulation.Thus, TCR downregulation seemed to depend solely on TCR/peptide/interaction and did not require either CD8 or B7-1 expression; ICAM-1 potentiated TCR downregulation, but only with limiting doses of peptides.TCR downregulation was most prominent with high affinity peptides and appeared to be neither obligatory nor sufficient for T cell activation.

View Article: PubMed Central - PubMed

Affiliation: Department of Immunology, IMM4, The Scripps Research Institute, La Jolla, California 92037, USA.

ABSTRACT
The requirements for inducing downregulation of alpha/beta T cell receptor (TCR) molecules on naive major histocompatibility complex class I-restricted T cells was investigated with 2C TCR transgenic mice and defined peptides as antigen. Confirming previous results, activation of 2C T cells in response to specific peptides required CD8 expression on the responder cells and was heavily dependent upon costimulation provided by either B7-1 or ICAM-1 on antigen-presenting cells (APC). These stringent requirements did not apply to TCR downregulation. Thus, TCR downregulation seemed to depend solely on TCR/peptide/interaction and did not require either CD8 or B7-1 expression; ICAM-1 potentiated TCR downregulation, but only with limiting doses of peptides. TCR downregulation was most prominent with high affinity peptides and appeared to be neither obligatory nor sufficient for T cell activation. In marked contrast to T cell activation, TCR downregulation was resistant to various metabolic inhibitors. The biological significance of TCR downregulation is unclear, but could be a device for protecting T cells against excessive signaling.

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Influence of 2C  CD8 expression on TCR downregulation and T cell activation.  (A) Proliferative responses of 2C  cells to B10.D2 spleen APCs ±  QL9 peptide. Purified CD8+ or  CD8− 2C cells (5 × 104) were  cultured with B10.D2 spleen  cells (5 × 105) in the absence or  presence of titrated concentrations of QL9 peptides for 3 d.  [3H]thymidine (1 μCi) was  added during the last 8 h of culture. (B) TCR downregulation  on 2C T cells. Purified CD8+ or  CD8− 2C T cells (5 × 105) were  cultured with T-depleted  B10.D2 spleen cells (5 × 106) in  the absence or presence of a titrated concentration of QL9 or  p2Ca peptides for 12 h. The cells  were harvested and stained for  TCR expression with FITCconjugated 1B2 mAb. The expression of TCR on 2C cells was  analyzed on gated Thy-1+ cells.
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Figure 3: Influence of 2C CD8 expression on TCR downregulation and T cell activation. (A) Proliferative responses of 2C cells to B10.D2 spleen APCs ± QL9 peptide. Purified CD8+ or CD8− 2C cells (5 × 104) were cultured with B10.D2 spleen cells (5 × 105) in the absence or presence of titrated concentrations of QL9 peptides for 3 d. [3H]thymidine (1 μCi) was added during the last 8 h of culture. (B) TCR downregulation on 2C T cells. Purified CD8+ or CD8− 2C T cells (5 × 105) were cultured with T-depleted B10.D2 spleen cells (5 × 106) in the absence or presence of a titrated concentration of QL9 or p2Ca peptides for 12 h. The cells were harvested and stained for TCR expression with FITCconjugated 1B2 mAb. The expression of TCR on 2C cells was analyzed on gated Thy-1+ cells.

Mentions: CD8 molecules function by augmenting TCR contact with peptide/MHC class I complexes on APCs and also by promoting intracellular signaling via association with p56lck (28, 29). In the absence of CD8 function, e.g., when anti-CD8 mAb is added to culture, the proliferative response of naive 2C CD8+ cells to B10.D2 spleen without added peptides is undetectable unless the cells are supplemented with exogenous cytokines (19); similar findings apply when the CD8− (CD4−8−) subset of 2C cells are used as responders. With addition of the strong QL9 peptide to B10.D2 spleen cells, however, CD8 function becomes redundant, implying that CD8 function is only required when the avidity of T/APC interaction is low (22). This is illustrated in Fig. 3 A where it can be seen that the clonotype-positive (1B2+) subset of CD8− 2C cells failed to proliferate in response to B10.D2 spleen cells without exogenous peptide but gave high responses to B10.D2 spleen supplemented with QL9 peptide (bottom). CD8+ 2C cells, by contrast, responded strongly to B10.D2 spleen in the absence of added peptide (top). As discussed elsewhere, CD8+ 2C cells behave identically to CD8− 2C cells when supplemented with anti-CD8 mAb (19), implying that the CD8− subset is not innately peculiar.


Requirements for peptide-induced T cell receptor downregulation on naive CD8+ T cells.

Cai Z, Kishimoto H, Brunmark A, Jackson MR, Peterson PA, Sprent J - J. Exp. Med. (1997)

Influence of 2C  CD8 expression on TCR downregulation and T cell activation.  (A) Proliferative responses of 2C  cells to B10.D2 spleen APCs ±  QL9 peptide. Purified CD8+ or  CD8− 2C cells (5 × 104) were  cultured with B10.D2 spleen  cells (5 × 105) in the absence or  presence of titrated concentrations of QL9 peptides for 3 d.  [3H]thymidine (1 μCi) was  added during the last 8 h of culture. (B) TCR downregulation  on 2C T cells. Purified CD8+ or  CD8− 2C T cells (5 × 105) were  cultured with T-depleted  B10.D2 spleen cells (5 × 106) in  the absence or presence of a titrated concentration of QL9 or  p2Ca peptides for 12 h. The cells  were harvested and stained for  TCR expression with FITCconjugated 1B2 mAb. The expression of TCR on 2C cells was  analyzed on gated Thy-1+ cells.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2196147&req=5

Figure 3: Influence of 2C CD8 expression on TCR downregulation and T cell activation. (A) Proliferative responses of 2C cells to B10.D2 spleen APCs ± QL9 peptide. Purified CD8+ or CD8− 2C cells (5 × 104) were cultured with B10.D2 spleen cells (5 × 105) in the absence or presence of titrated concentrations of QL9 peptides for 3 d. [3H]thymidine (1 μCi) was added during the last 8 h of culture. (B) TCR downregulation on 2C T cells. Purified CD8+ or CD8− 2C T cells (5 × 105) were cultured with T-depleted B10.D2 spleen cells (5 × 106) in the absence or presence of a titrated concentration of QL9 or p2Ca peptides for 12 h. The cells were harvested and stained for TCR expression with FITCconjugated 1B2 mAb. The expression of TCR on 2C cells was analyzed on gated Thy-1+ cells.
Mentions: CD8 molecules function by augmenting TCR contact with peptide/MHC class I complexes on APCs and also by promoting intracellular signaling via association with p56lck (28, 29). In the absence of CD8 function, e.g., when anti-CD8 mAb is added to culture, the proliferative response of naive 2C CD8+ cells to B10.D2 spleen without added peptides is undetectable unless the cells are supplemented with exogenous cytokines (19); similar findings apply when the CD8− (CD4−8−) subset of 2C cells are used as responders. With addition of the strong QL9 peptide to B10.D2 spleen cells, however, CD8 function becomes redundant, implying that CD8 function is only required when the avidity of T/APC interaction is low (22). This is illustrated in Fig. 3 A where it can be seen that the clonotype-positive (1B2+) subset of CD8− 2C cells failed to proliferate in response to B10.D2 spleen cells without exogenous peptide but gave high responses to B10.D2 spleen supplemented with QL9 peptide (bottom). CD8+ 2C cells, by contrast, responded strongly to B10.D2 spleen in the absence of added peptide (top). As discussed elsewhere, CD8+ 2C cells behave identically to CD8− 2C cells when supplemented with anti-CD8 mAb (19), implying that the CD8− subset is not innately peculiar.

Bottom Line: These stringent requirements did not apply to TCR downregulation.Thus, TCR downregulation seemed to depend solely on TCR/peptide/interaction and did not require either CD8 or B7-1 expression; ICAM-1 potentiated TCR downregulation, but only with limiting doses of peptides.TCR downregulation was most prominent with high affinity peptides and appeared to be neither obligatory nor sufficient for T cell activation.

View Article: PubMed Central - PubMed

Affiliation: Department of Immunology, IMM4, The Scripps Research Institute, La Jolla, California 92037, USA.

ABSTRACT
The requirements for inducing downregulation of alpha/beta T cell receptor (TCR) molecules on naive major histocompatibility complex class I-restricted T cells was investigated with 2C TCR transgenic mice and defined peptides as antigen. Confirming previous results, activation of 2C T cells in response to specific peptides required CD8 expression on the responder cells and was heavily dependent upon costimulation provided by either B7-1 or ICAM-1 on antigen-presenting cells (APC). These stringent requirements did not apply to TCR downregulation. Thus, TCR downregulation seemed to depend solely on TCR/peptide/interaction and did not require either CD8 or B7-1 expression; ICAM-1 potentiated TCR downregulation, but only with limiting doses of peptides. TCR downregulation was most prominent with high affinity peptides and appeared to be neither obligatory nor sufficient for T cell activation. In marked contrast to T cell activation, TCR downregulation was resistant to various metabolic inhibitors. The biological significance of TCR downregulation is unclear, but could be a device for protecting T cells against excessive signaling.

Show MeSH
Related in: MedlinePlus