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Cathepsin L regulates CD4+ T cell selection independently of its effect on invariant chain: a role in the generation of positively selecting peptide ligands.

Honey K, Nakagawa T, Peters C, Rudensky A - J. Exp. Med. (2002)

Bottom Line: Molecules regulating this peptide presentation play a role in determining the outcome of positive selection.Our data indicate the cathepsin L defect in CD4+ T cell selection is haplotype independent, and thus imply it is independent of invariant chain degradation.This was confirmed by analysis of I-A(b) mice deficient in both cathepsin L and invariant chain.

View Article: PubMed Central - PubMed

Affiliation: Department of Immunology, University of Washington School of Medicine, Seattle, WA 98195, USA.

ABSTRACT
CD4+ T cells are positively selected in the thymus on peptides presented in the context of major histocompatibility complex class II molecules expressed on cortical thymic epithelial cells. Molecules regulating this peptide presentation play a role in determining the outcome of positive selection. Cathepsin L mediates invariant chain processing in cortical thymic epithelial cells, and animals of the I-A(b) haplotype deficient in this enzyme exhibit impaired CD4+ T cell selection. To determine whether the selection defect is due solely to the block in invariant chain cleavage we analyzed cathepsin L-deficient mice expressing the I-A(q) haplotype which has little dependence upon invariant chain processing for peptide presentation. Our data indicate the cathepsin L defect in CD4+ T cell selection is haplotype independent, and thus imply it is independent of invariant chain degradation. This was confirmed by analysis of I-A(b) mice deficient in both cathepsin L and invariant chain. We show that the defect in positive selection in the cathepsin L-/- thymus is specific for CD4+ T cells that can be selected in a wild-type and provide evidence that the repertoire of T cells selected differs from that in wild-type mice, suggesting cortical thymic epithelial cells in cathepsin L knockout mice express an altered peptide repertoire. Thus, we propose a novel role for cathepsin L in regulating positive selection by generating the major histocompatibility complex class II bound peptide ligands presented by cortical thymic epithelial cells.

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Impaired selection of CD4+ but not CD8+ T cell receptor transgenic T cells in cathepsin L–deficient mice. Bone marrow isolated from either CD4+ TCR transgenic (TCli) or CD8+ TCR transgenic (OT-1) mice was transplanted into lethally irradiated catL−/− and BL6 mice. The spleen and thymus of chimeric mice were analyzed by flow cytometry 8 wk after bone marrow transplantation. The percentage of donor T cells was determined by CD4+ Vβ6+ staining for TCli recipients (A) and CD8+ Vβ5+ staining for OT-1 recipients (B). The data shown are representative of three independent experiments with two to three mice per group.
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fig1: Impaired selection of CD4+ but not CD8+ T cell receptor transgenic T cells in cathepsin L–deficient mice. Bone marrow isolated from either CD4+ TCR transgenic (TCli) or CD8+ TCR transgenic (OT-1) mice was transplanted into lethally irradiated catL−/− and BL6 mice. The spleen and thymus of chimeric mice were analyzed by flow cytometry 8 wk after bone marrow transplantation. The percentage of donor T cells was determined by CD4+ Vβ6+ staining for TCli recipients (A) and CD8+ Vβ5+ staining for OT-1 recipients (B). The data shown are representative of three independent experiments with two to three mice per group.

Mentions: We transferred bone marrow from either a MHC class II–restricted TCR transgenic mouse (TCli) or a MHC class I–restricted TCR transgenic mouse (OT-1) into lethally irradiated catL−/− or wild-type mice. The TCR transgenic donors were on a RAG−/− background to prevent endogenous α-chain rearrangement during selection. Chimerism was >92% in all animals analyzed (data not shown). Analysis of splenocytes and thymocytes from TCli bone marrow recipients indicated that selection of the transgenic T cells (CD4+ Vβ6+) was almost completely abrogated in catL deficient recipients (Fig. 1 A). Selection of OT-1 TCR transgenic T cells (CD8+ Vβ5+), however, occurred normally in catL−/− hosts (Fig. 1 B). This observation that transgenic CD4+ T cells cannot be positively selected by the catL-deficient thymic environment while selection of CD8+ T cells is not impaired, indicates that catL is not essential for maintenance of a viable positive selection environment but that its effect is specific for CD4+ T cells. Thus, this result suggests the MHC class II peptide repertoire expressed at the surface of catL−/− cTECs is altered such that it cannot support efficient selection of CD4+ T cells that develop in wild-type mice.


Cathepsin L regulates CD4+ T cell selection independently of its effect on invariant chain: a role in the generation of positively selecting peptide ligands.

Honey K, Nakagawa T, Peters C, Rudensky A - J. Exp. Med. (2002)

Impaired selection of CD4+ but not CD8+ T cell receptor transgenic T cells in cathepsin L–deficient mice. Bone marrow isolated from either CD4+ TCR transgenic (TCli) or CD8+ TCR transgenic (OT-1) mice was transplanted into lethally irradiated catL−/− and BL6 mice. The spleen and thymus of chimeric mice were analyzed by flow cytometry 8 wk after bone marrow transplantation. The percentage of donor T cells was determined by CD4+ Vβ6+ staining for TCli recipients (A) and CD8+ Vβ5+ staining for OT-1 recipients (B). The data shown are representative of three independent experiments with two to three mice per group.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2193748&req=5

fig1: Impaired selection of CD4+ but not CD8+ T cell receptor transgenic T cells in cathepsin L–deficient mice. Bone marrow isolated from either CD4+ TCR transgenic (TCli) or CD8+ TCR transgenic (OT-1) mice was transplanted into lethally irradiated catL−/− and BL6 mice. The spleen and thymus of chimeric mice were analyzed by flow cytometry 8 wk after bone marrow transplantation. The percentage of donor T cells was determined by CD4+ Vβ6+ staining for TCli recipients (A) and CD8+ Vβ5+ staining for OT-1 recipients (B). The data shown are representative of three independent experiments with two to three mice per group.
Mentions: We transferred bone marrow from either a MHC class II–restricted TCR transgenic mouse (TCli) or a MHC class I–restricted TCR transgenic mouse (OT-1) into lethally irradiated catL−/− or wild-type mice. The TCR transgenic donors were on a RAG−/− background to prevent endogenous α-chain rearrangement during selection. Chimerism was >92% in all animals analyzed (data not shown). Analysis of splenocytes and thymocytes from TCli bone marrow recipients indicated that selection of the transgenic T cells (CD4+ Vβ6+) was almost completely abrogated in catL deficient recipients (Fig. 1 A). Selection of OT-1 TCR transgenic T cells (CD8+ Vβ5+), however, occurred normally in catL−/− hosts (Fig. 1 B). This observation that transgenic CD4+ T cells cannot be positively selected by the catL-deficient thymic environment while selection of CD8+ T cells is not impaired, indicates that catL is not essential for maintenance of a viable positive selection environment but that its effect is specific for CD4+ T cells. Thus, this result suggests the MHC class II peptide repertoire expressed at the surface of catL−/− cTECs is altered such that it cannot support efficient selection of CD4+ T cells that develop in wild-type mice.

Bottom Line: Molecules regulating this peptide presentation play a role in determining the outcome of positive selection.Our data indicate the cathepsin L defect in CD4+ T cell selection is haplotype independent, and thus imply it is independent of invariant chain degradation.This was confirmed by analysis of I-A(b) mice deficient in both cathepsin L and invariant chain.

View Article: PubMed Central - PubMed

Affiliation: Department of Immunology, University of Washington School of Medicine, Seattle, WA 98195, USA.

ABSTRACT
CD4+ T cells are positively selected in the thymus on peptides presented in the context of major histocompatibility complex class II molecules expressed on cortical thymic epithelial cells. Molecules regulating this peptide presentation play a role in determining the outcome of positive selection. Cathepsin L mediates invariant chain processing in cortical thymic epithelial cells, and animals of the I-A(b) haplotype deficient in this enzyme exhibit impaired CD4+ T cell selection. To determine whether the selection defect is due solely to the block in invariant chain cleavage we analyzed cathepsin L-deficient mice expressing the I-A(q) haplotype which has little dependence upon invariant chain processing for peptide presentation. Our data indicate the cathepsin L defect in CD4+ T cell selection is haplotype independent, and thus imply it is independent of invariant chain degradation. This was confirmed by analysis of I-A(b) mice deficient in both cathepsin L and invariant chain. We show that the defect in positive selection in the cathepsin L-/- thymus is specific for CD4+ T cells that can be selected in a wild-type and provide evidence that the repertoire of T cells selected differs from that in wild-type mice, suggesting cortical thymic epithelial cells in cathepsin L knockout mice express an altered peptide repertoire. Thus, we propose a novel role for cathepsin L in regulating positive selection by generating the major histocompatibility complex class II bound peptide ligands presented by cortical thymic epithelial cells.

Show MeSH
Related in: MedlinePlus