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The common cytokine receptor gamma chain and the pre-T cell receptor provide independent but critically overlapping signals in early alpha/beta T cell development.

Di Santo JP, Aifantis I, Rosmaraki E, Garcia C, Feinberg J, Fehling HJ, Fischer A, von Boehmer H, Rocha B - J. Exp. Med. (1999)

Bottom Line: Interleukin (IL)-7 interactions with its cognate receptor complex (IL-7Ralpha coupled to the common cytokine receptor gamma chain, gammac) play a dominant role in early thymopoiesis.We demonstrate that gammac-dependent cytokines do not appear to be required for normal pre-TCR function, and that the rate-limiting step in alpha/beta T cell development in gammac- mice does not involve TCR-beta chain rearrangements, but rather results from poor maintenance of early thymocytes.Thus, a series of overlapping signals derived from cytokine and T cell receptors guide the process of alpha/beta thymocyte development.

View Article: PubMed Central - PubMed

Affiliation: Institut National de la Santé et de la Recherche Médicale (INSERM) U429, Hôpital Necker-Enfants Malades, F-75743 Paris, France. disanto@nexker.fr

ABSTRACT
Intracellular signals emanating from cytokine and antigen receptors are integrated during the process of intrathymic development. Still, the relative contributions of cytokine receptor signaling to pre-T cell receptor (TCR) and TCR-mediated differentiation remain undefined. Interleukin (IL)-7 interactions with its cognate receptor complex (IL-7Ralpha coupled to the common cytokine receptor gamma chain, gammac) play a dominant role in early thymopoiesis. However, alpha/beta T cell development in IL-7-, IL-7Ralpha-, and gammac-deficient mice is only partially compromised, suggesting that additional pathways can rescue alpha/beta T lineage cells in these mice. We have investigated the potential interdependence of gammac- and pre-TCR-dependent pathways during intrathymic alpha/beta T cell differentiation. We demonstrate that gammac-dependent cytokines do not appear to be required for normal pre-TCR function, and that the rate-limiting step in alpha/beta T cell development in gammac- mice does not involve TCR-beta chain rearrangements, but rather results from poor maintenance of early thymocytes. Moreover, mice double mutant for both gammac and pre-Talpha show vastly reduced thymic cellularity and a complete arrest of thymocyte differentiation at the CD44(+)CD25(+) cell stage. These observations demonstrate that the pre-TCR provides the gammac-independent signal which allows alpha/beta T cell development in gammac- mice. Thus, a series of overlapping signals derived from cytokine and T cell receptors guide the process of alpha/beta thymocyte development.

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Intracellular expression of pTα and TCR-β chain in  CD25+ thymocyte precursors.  Thymocytes from γc+ or γc−  mice were surface stained for TN  cells (see Fig. 1), CD44, and  CD25, fixed, and permeabilized  with saponin before detection of  intracellular (IC) TCR-β or pTα  chains. Gated CD44+CD25+ and  CD44−CD25+ thymocyte subsets are boxed. Negative controls  (dotted lines) are staining of thymocytes from RAG-2–deficient  (for TCR-β) or pTα-deficient  (for pTα) mice.
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Figure 5: Intracellular expression of pTα and TCR-β chain in CD25+ thymocyte precursors. Thymocytes from γc+ or γc− mice were surface stained for TN cells (see Fig. 1), CD44, and CD25, fixed, and permeabilized with saponin before detection of intracellular (IC) TCR-β or pTα chains. Gated CD44+CD25+ and CD44−CD25+ thymocyte subsets are boxed. Negative controls (dotted lines) are staining of thymocytes from RAG-2–deficient (for TCR-β) or pTα-deficient (for pTα) mice.

Mentions: It would follow from these results that a pre-TCR can form at the CD44+CD25+ stage. Although several studies have reported the rearrangement status of early thymocyte subsets (40, 46, 49), no studies to date have examined pre-TCR protein expression in these cells. Using reagents specific for the TCR-β (29) and a newly developed antibody against the pTα chain (30), we characterized intracellular pre-TCR components in early thymocytes from γc+ and γc− mice (Fig. 5). At the CD44+CD25+ stage, thymocytes demonstrate uniform intracellular staining for pTα chains, whereas the level of pTα expression increases slightly as the cells mature to become CD44−CD25+. A small fraction of CD44+CD25+ cells (3.0 ± 1%; n = 4) also stain intracellularly for TCR-β protein; this fraction increases to ∼20% as these cells downregulate CD44 expression (Fig. 5). TCR-β and pTα protein expression on a per cell basis was not qualitatively or quantitatively altered in γc− thymocytes (Fig. 5). These data conclusively demonstrate that a pre-TCR can form during the CD44+CD25+ to CD44−CD25+ transition, a point at which intrathymic precursors express IL-7Rα/γc (41). These results suggest that γc and pre-TCR signals are independent and overlapping for intrathymic development.


The common cytokine receptor gamma chain and the pre-T cell receptor provide independent but critically overlapping signals in early alpha/beta T cell development.

Di Santo JP, Aifantis I, Rosmaraki E, Garcia C, Feinberg J, Fehling HJ, Fischer A, von Boehmer H, Rocha B - J. Exp. Med. (1999)

Intracellular expression of pTα and TCR-β chain in  CD25+ thymocyte precursors.  Thymocytes from γc+ or γc−  mice were surface stained for TN  cells (see Fig. 1), CD44, and  CD25, fixed, and permeabilized  with saponin before detection of  intracellular (IC) TCR-β or pTα  chains. Gated CD44+CD25+ and  CD44−CD25+ thymocyte subsets are boxed. Negative controls  (dotted lines) are staining of thymocytes from RAG-2–deficient  (for TCR-β) or pTα-deficient  (for pTα) mice.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2192922&req=5

Figure 5: Intracellular expression of pTα and TCR-β chain in CD25+ thymocyte precursors. Thymocytes from γc+ or γc− mice were surface stained for TN cells (see Fig. 1), CD44, and CD25, fixed, and permeabilized with saponin before detection of intracellular (IC) TCR-β or pTα chains. Gated CD44+CD25+ and CD44−CD25+ thymocyte subsets are boxed. Negative controls (dotted lines) are staining of thymocytes from RAG-2–deficient (for TCR-β) or pTα-deficient (for pTα) mice.
Mentions: It would follow from these results that a pre-TCR can form at the CD44+CD25+ stage. Although several studies have reported the rearrangement status of early thymocyte subsets (40, 46, 49), no studies to date have examined pre-TCR protein expression in these cells. Using reagents specific for the TCR-β (29) and a newly developed antibody against the pTα chain (30), we characterized intracellular pre-TCR components in early thymocytes from γc+ and γc− mice (Fig. 5). At the CD44+CD25+ stage, thymocytes demonstrate uniform intracellular staining for pTα chains, whereas the level of pTα expression increases slightly as the cells mature to become CD44−CD25+. A small fraction of CD44+CD25+ cells (3.0 ± 1%; n = 4) also stain intracellularly for TCR-β protein; this fraction increases to ∼20% as these cells downregulate CD44 expression (Fig. 5). TCR-β and pTα protein expression on a per cell basis was not qualitatively or quantitatively altered in γc− thymocytes (Fig. 5). These data conclusively demonstrate that a pre-TCR can form during the CD44+CD25+ to CD44−CD25+ transition, a point at which intrathymic precursors express IL-7Rα/γc (41). These results suggest that γc and pre-TCR signals are independent and overlapping for intrathymic development.

Bottom Line: Interleukin (IL)-7 interactions with its cognate receptor complex (IL-7Ralpha coupled to the common cytokine receptor gamma chain, gammac) play a dominant role in early thymopoiesis.We demonstrate that gammac-dependent cytokines do not appear to be required for normal pre-TCR function, and that the rate-limiting step in alpha/beta T cell development in gammac- mice does not involve TCR-beta chain rearrangements, but rather results from poor maintenance of early thymocytes.Thus, a series of overlapping signals derived from cytokine and T cell receptors guide the process of alpha/beta thymocyte development.

View Article: PubMed Central - PubMed

Affiliation: Institut National de la Santé et de la Recherche Médicale (INSERM) U429, Hôpital Necker-Enfants Malades, F-75743 Paris, France. disanto@nexker.fr

ABSTRACT
Intracellular signals emanating from cytokine and antigen receptors are integrated during the process of intrathymic development. Still, the relative contributions of cytokine receptor signaling to pre-T cell receptor (TCR) and TCR-mediated differentiation remain undefined. Interleukin (IL)-7 interactions with its cognate receptor complex (IL-7Ralpha coupled to the common cytokine receptor gamma chain, gammac) play a dominant role in early thymopoiesis. However, alpha/beta T cell development in IL-7-, IL-7Ralpha-, and gammac-deficient mice is only partially compromised, suggesting that additional pathways can rescue alpha/beta T lineage cells in these mice. We have investigated the potential interdependence of gammac- and pre-TCR-dependent pathways during intrathymic alpha/beta T cell differentiation. We demonstrate that gammac-dependent cytokines do not appear to be required for normal pre-TCR function, and that the rate-limiting step in alpha/beta T cell development in gammac- mice does not involve TCR-beta chain rearrangements, but rather results from poor maintenance of early thymocytes. Moreover, mice double mutant for both gammac and pre-Talpha show vastly reduced thymic cellularity and a complete arrest of thymocyte differentiation at the CD44(+)CD25(+) cell stage. These observations demonstrate that the pre-TCR provides the gammac-independent signal which allows alpha/beta T cell development in gammac- mice. Thus, a series of overlapping signals derived from cytokine and T cell receptors guide the process of alpha/beta thymocyte development.

Show MeSH
Related in: MedlinePlus