Limits...
Quantitative impact of thymic clonal deletion on the T cell repertoire.

van Meerwijk JP, Marguerat S, Lees RK, Germain RN, Fowlkes BJ, MacDonald HR - J. Exp. Med. (1997)

Bottom Line: Interactions between major histocompatibility complex (MHC) molecules expressed on stromal cells and antigen-specific receptors on T cells shape the repertoire of mature T lymphocytes emerging from the thymus.The quantitative impact of negative selection on the potentially available repertoire is currently unknown.To address this issue, we have constructed radiation bone marrow chimeras in which MHC molecules are present on radioresistant thymic epithelial cells (to allow positive selection) but absent from radiosensitive hematopoietic elements responsible for negative selection.

View Article: PubMed Central - PubMed

Affiliation: Ludwig Institute for Cancer Research, University of Lausanne, Epalinges, Switzerland.

ABSTRACT
Interactions between major histocompatibility complex (MHC) molecules expressed on stromal cells and antigen-specific receptors on T cells shape the repertoire of mature T lymphocytes emerging from the thymus. Some thymocytes with appropriate receptors are stimulated to undergo differentiation to the fully mature state (positive selection), whereas others with strongly autoreactive receptors are triggered to undergo programmed cell death before completing this differentiation process (negative selection). The quantitative impact of negative selection on the potentially available repertoire is currently unknown. To address this issue, we have constructed radiation bone marrow chimeras in which MHC molecules are present on radioresistant thymic epithelial cells (to allow positive selection) but absent from radiosensitive hematopoietic elements responsible for negative selection. In such chimeras, the number of mature thymocytes was increased by twofold as compared with appropriate control chimeras This increase in steady-state numbers of mature thymocytes was not related to proliferation, increased retention, or recirculation and was accompanied by a similar two- to threefold increase in the de novo rate of generation of mature cells. Taken together, our data indicate that half to two-thirds of the thymocytes able to undergo positive selection die before full maturation due to negative selection.

Show MeSH

Related in: MedlinePlus

Increased CD4SP (CD4+CD8−TCRhigh) thymocytes in chimeras lacking MHC class II expression on hematopoietic elements.  Groups of sex- and age-matched chimeras were analyzed on the same day  6–8 wk after engraftment. Flow cytometry was performed using antiTCR, anti-CD4, and anti-CD8 antibodies. In each experiment, the ratio  of CD4SP cells in the indicated groups was calculated. Error bars indicate  SD. The increased ratio of CD4SP cells in MHC II°→ MHC I° versus  MHC II+→ MHC I° chimeras is statistically significant as assessed by the  Student's t test (P <0.0001), whereas the ratio of CD4SP thymocytes in  MHC I°→ MHC I° versus MHC I+→ MHC I° chimeras is not significantly increased (P = 0.02).
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2196036&req=5

Figure 2: Increased CD4SP (CD4+CD8−TCRhigh) thymocytes in chimeras lacking MHC class II expression on hematopoietic elements. Groups of sex- and age-matched chimeras were analyzed on the same day 6–8 wk after engraftment. Flow cytometry was performed using antiTCR, anti-CD4, and anti-CD8 antibodies. In each experiment, the ratio of CD4SP cells in the indicated groups was calculated. Error bars indicate SD. The increased ratio of CD4SP cells in MHC II°→ MHC I° versus MHC II+→ MHC I° chimeras is statistically significant as assessed by the Student's t test (P <0.0001), whereas the ratio of CD4SP thymocytes in MHC I°→ MHC I° versus MHC I+→ MHC I° chimeras is not significantly increased (P = 0.02).

Mentions: Single-cell suspensions of thymocytes were incubated on ice with saturating concentrations of the following antibodies: Fig. 1, anti-CD8–FITC, anti-TCR–PE (PharMingen, San Diego, CA), and anti-CD4–Red613 (GIBCO BRL, Gaithersburg, MD); Figs. 2 and 4, anti-TCR–FITC (H57-597), anti-CD4–PE (Boehringer-Mannheim, Mannheim, Federal Republic of Germany), and anti-CD8–Red613 (GIBCO BRL, Gaithersburg, MD). The samples were analyzed on a FACScan® using LYSYS II software (Becton Dickinson, Mountain View, CA).


Quantitative impact of thymic clonal deletion on the T cell repertoire.

van Meerwijk JP, Marguerat S, Lees RK, Germain RN, Fowlkes BJ, MacDonald HR - J. Exp. Med. (1997)

Increased CD4SP (CD4+CD8−TCRhigh) thymocytes in chimeras lacking MHC class II expression on hematopoietic elements.  Groups of sex- and age-matched chimeras were analyzed on the same day  6–8 wk after engraftment. Flow cytometry was performed using antiTCR, anti-CD4, and anti-CD8 antibodies. In each experiment, the ratio  of CD4SP cells in the indicated groups was calculated. Error bars indicate  SD. The increased ratio of CD4SP cells in MHC II°→ MHC I° versus  MHC II+→ MHC I° chimeras is statistically significant as assessed by the  Student's t test (P <0.0001), whereas the ratio of CD4SP thymocytes in  MHC I°→ MHC I° versus MHC I+→ MHC I° chimeras is not significantly increased (P = 0.02).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2196036&req=5

Figure 2: Increased CD4SP (CD4+CD8−TCRhigh) thymocytes in chimeras lacking MHC class II expression on hematopoietic elements. Groups of sex- and age-matched chimeras were analyzed on the same day 6–8 wk after engraftment. Flow cytometry was performed using antiTCR, anti-CD4, and anti-CD8 antibodies. In each experiment, the ratio of CD4SP cells in the indicated groups was calculated. Error bars indicate SD. The increased ratio of CD4SP cells in MHC II°→ MHC I° versus MHC II+→ MHC I° chimeras is statistically significant as assessed by the Student's t test (P <0.0001), whereas the ratio of CD4SP thymocytes in MHC I°→ MHC I° versus MHC I+→ MHC I° chimeras is not significantly increased (P = 0.02).
Mentions: Single-cell suspensions of thymocytes were incubated on ice with saturating concentrations of the following antibodies: Fig. 1, anti-CD8–FITC, anti-TCR–PE (PharMingen, San Diego, CA), and anti-CD4–Red613 (GIBCO BRL, Gaithersburg, MD); Figs. 2 and 4, anti-TCR–FITC (H57-597), anti-CD4–PE (Boehringer-Mannheim, Mannheim, Federal Republic of Germany), and anti-CD8–Red613 (GIBCO BRL, Gaithersburg, MD). The samples were analyzed on a FACScan® using LYSYS II software (Becton Dickinson, Mountain View, CA).

Bottom Line: Interactions between major histocompatibility complex (MHC) molecules expressed on stromal cells and antigen-specific receptors on T cells shape the repertoire of mature T lymphocytes emerging from the thymus.The quantitative impact of negative selection on the potentially available repertoire is currently unknown.To address this issue, we have constructed radiation bone marrow chimeras in which MHC molecules are present on radioresistant thymic epithelial cells (to allow positive selection) but absent from radiosensitive hematopoietic elements responsible for negative selection.

View Article: PubMed Central - PubMed

Affiliation: Ludwig Institute for Cancer Research, University of Lausanne, Epalinges, Switzerland.

ABSTRACT
Interactions between major histocompatibility complex (MHC) molecules expressed on stromal cells and antigen-specific receptors on T cells shape the repertoire of mature T lymphocytes emerging from the thymus. Some thymocytes with appropriate receptors are stimulated to undergo differentiation to the fully mature state (positive selection), whereas others with strongly autoreactive receptors are triggered to undergo programmed cell death before completing this differentiation process (negative selection). The quantitative impact of negative selection on the potentially available repertoire is currently unknown. To address this issue, we have constructed radiation bone marrow chimeras in which MHC molecules are present on radioresistant thymic epithelial cells (to allow positive selection) but absent from radiosensitive hematopoietic elements responsible for negative selection. In such chimeras, the number of mature thymocytes was increased by twofold as compared with appropriate control chimeras This increase in steady-state numbers of mature thymocytes was not related to proliferation, increased retention, or recirculation and was accompanied by a similar two- to threefold increase in the de novo rate of generation of mature cells. Taken together, our data indicate that half to two-thirds of the thymocytes able to undergo positive selection die before full maturation due to negative selection.

Show MeSH
Related in: MedlinePlus