Limits...
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.

Show MeSH
Effects of CCD on TCR downregulation and T cell activation. Purified CD8+ 2C cells (5 × 105) were cultured with 1 × 106 Drosophila  APCs (top, Ld.B7 cells and bottom Ld.ICAM cells) in the presence of a titrated dose of QL9 peptide for 12 h. CCD was added at the beginning of the culture at a final concentration of 4 μg/ml. The cells were harvested and stained for FITC-conjugated anti-CD25, FITC-conjugated anti-CD69, or FITCconjugated 1B2 (TCR) mAbs. The cells were analyzed on a FACScan and the data show the mean fluorescence intensity (MFI) on gated CD8+ 2C cells  stained with each mAb. The data in A and B are from different experiments.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2196147&req=5

Figure 6: Effects of CCD on TCR downregulation and T cell activation. Purified CD8+ 2C cells (5 × 105) were cultured with 1 × 106 Drosophila APCs (top, Ld.B7 cells and bottom Ld.ICAM cells) in the presence of a titrated dose of QL9 peptide for 12 h. CCD was added at the beginning of the culture at a final concentration of 4 μg/ml. The cells were harvested and stained for FITC-conjugated anti-CD25, FITC-conjugated anti-CD69, or FITCconjugated 1B2 (TCR) mAbs. The cells were analyzed on a FACScan and the data show the mean fluorescence intensity (MFI) on gated CD8+ 2C cells stained with each mAb. The data in A and B are from different experiments.

Mentions: The effects of adding CCD to 2C cells cultured with Ld.B7 versus Ld.ICAM Drosophila APCs plus graded concentrations of QL9 peptide are shown in Fig. 6 A. In the case of TCR expression, CCD had only a very mild effect in reducing TCR downregulation. This effect was seen in several different experiments and tended to be slightly more pronounced for Ld.ICAM than Ld.B7 APCs (see also Fig. 6 B, right). For CD25 (IL-2Rα) and CD69 expression, however, the results were much more dramatic (Fig. 6 B). Thus, with Ld.ICAM APCs, addition of CCD profoundly reduced upregulation of CD25 and CD69 expression, especially at low concentrations of peptide. With Ld.B7 APCs, by contrast, CCD failed to impair CD25 or CD69 upregulation; indeed, the upregulation of these markers was slightly increased in the presence of CCD. The implications of these findings will be discussed later.


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)

Effects of CCD on TCR downregulation and T cell activation. Purified CD8+ 2C cells (5 × 105) were cultured with 1 × 106 Drosophila  APCs (top, Ld.B7 cells and bottom Ld.ICAM cells) in the presence of a titrated dose of QL9 peptide for 12 h. CCD was added at the beginning of the culture at a final concentration of 4 μg/ml. The cells were harvested and stained for FITC-conjugated anti-CD25, FITC-conjugated anti-CD69, or FITCconjugated 1B2 (TCR) mAbs. The cells were analyzed on a FACScan and the data show the mean fluorescence intensity (MFI) on gated CD8+ 2C cells  stained with each mAb. The data in A and B are from different experiments.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2196147&req=5

Figure 6: Effects of CCD on TCR downregulation and T cell activation. Purified CD8+ 2C cells (5 × 105) were cultured with 1 × 106 Drosophila APCs (top, Ld.B7 cells and bottom Ld.ICAM cells) in the presence of a titrated dose of QL9 peptide for 12 h. CCD was added at the beginning of the culture at a final concentration of 4 μg/ml. The cells were harvested and stained for FITC-conjugated anti-CD25, FITC-conjugated anti-CD69, or FITCconjugated 1B2 (TCR) mAbs. The cells were analyzed on a FACScan and the data show the mean fluorescence intensity (MFI) on gated CD8+ 2C cells stained with each mAb. The data in A and B are from different experiments.
Mentions: The effects of adding CCD to 2C cells cultured with Ld.B7 versus Ld.ICAM Drosophila APCs plus graded concentrations of QL9 peptide are shown in Fig. 6 A. In the case of TCR expression, CCD had only a very mild effect in reducing TCR downregulation. This effect was seen in several different experiments and tended to be slightly more pronounced for Ld.ICAM than Ld.B7 APCs (see also Fig. 6 B, right). For CD25 (IL-2Rα) and CD69 expression, however, the results were much more dramatic (Fig. 6 B). Thus, with Ld.ICAM APCs, addition of CCD profoundly reduced upregulation of CD25 and CD69 expression, especially at low concentrations of peptide. With Ld.B7 APCs, by contrast, CCD failed to impair CD25 or CD69 upregulation; indeed, the upregulation of these markers was slightly increased in the presence of CCD. The implications of these findings will be discussed later.

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