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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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Altered survival and proliferation of early thymocyte precursors in the  absence of γc. (A) Abnormal BrdU incorporation in γc− thymocytes. Mice received a  single pulse of BrdU before killing. Indicated thymocyte subsets were sorted, and  percentages of cells incorporating BrdU  were analyzed. (B) Annexin V staining of  γc+ or γc− thymocyte subsets. Cells were  stained for TN cells (see Fig. 1), CD25, and  Annexin V. Propidium iodide–negative  CD25− and CD25+ TN cells were electronically gated, and percentages of Annexin V–positive cells were calculated  (mean ± SD) from four mice of each genotype. (C) Intracellular Bcl-2 staining of DN  thymocyte precursors was performed; γc−  thymocytes demonstrated severely reduced  Bcl-2 levels (thick lines). Thin lines, isotype  control staining.
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Figure 2: Altered survival and proliferation of early thymocyte precursors in the absence of γc. (A) Abnormal BrdU incorporation in γc− thymocytes. Mice received a single pulse of BrdU before killing. Indicated thymocyte subsets were sorted, and percentages of cells incorporating BrdU were analyzed. (B) Annexin V staining of γc+ or γc− thymocyte subsets. Cells were stained for TN cells (see Fig. 1), CD25, and Annexin V. Propidium iodide–negative CD25− and CD25+ TN cells were electronically gated, and percentages of Annexin V–positive cells were calculated (mean ± SD) from four mice of each genotype. (C) Intracellular Bcl-2 staining of DN thymocyte precursors was performed; γc− thymocytes demonstrated severely reduced Bcl-2 levels (thick lines). Thin lines, isotype control staining.

Mentions: The block in thymocyte maturation seen in γc− thymi could result from abnormal differentiation, reduced cell survival, and/or proliferative defects. The ability of γc− thymocyte precursors to incorporate the analogue BrdU was used as a measure of intrathymic proliferation. The number of cells in S phase of the cell cycle was analyzed after a single injection of BrdU (Fig. 2 A). Only a fraction of the immature thymocytes are labeled under these conditions, and it is clear that T cell precursors in γc− mice show defects in proliferation, as both CD44+CD25− and CD44+CD25+ cells have markedly reduced BrdU incorporation relative to their γc+ counterparts (the CD44−CD25+ and CD44−CD25− subsets were not analyzed in γc− thymi due to their extremely small absolute numbers; these subsets were normally labeled in γc+ controls [data not shown]). DP cells from γc− mice were similarly affected.


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)

Altered survival and proliferation of early thymocyte precursors in the  absence of γc. (A) Abnormal BrdU incorporation in γc− thymocytes. Mice received a  single pulse of BrdU before killing. Indicated thymocyte subsets were sorted, and  percentages of cells incorporating BrdU  were analyzed. (B) Annexin V staining of  γc+ or γc− thymocyte subsets. Cells were  stained for TN cells (see Fig. 1), CD25, and  Annexin V. Propidium iodide–negative  CD25− and CD25+ TN cells were electronically gated, and percentages of Annexin V–positive cells were calculated  (mean ± SD) from four mice of each genotype. (C) Intracellular Bcl-2 staining of DN  thymocyte precursors was performed; γc−  thymocytes demonstrated severely reduced  Bcl-2 levels (thick lines). Thin lines, isotype  control staining.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2192922&req=5

Figure 2: Altered survival and proliferation of early thymocyte precursors in the absence of γc. (A) Abnormal BrdU incorporation in γc− thymocytes. Mice received a single pulse of BrdU before killing. Indicated thymocyte subsets were sorted, and percentages of cells incorporating BrdU were analyzed. (B) Annexin V staining of γc+ or γc− thymocyte subsets. Cells were stained for TN cells (see Fig. 1), CD25, and Annexin V. Propidium iodide–negative CD25− and CD25+ TN cells were electronically gated, and percentages of Annexin V–positive cells were calculated (mean ± SD) from four mice of each genotype. (C) Intracellular Bcl-2 staining of DN thymocyte precursors was performed; γc− thymocytes demonstrated severely reduced Bcl-2 levels (thick lines). Thin lines, isotype control staining.
Mentions: The block in thymocyte maturation seen in γc− thymi could result from abnormal differentiation, reduced cell survival, and/or proliferative defects. The ability of γc− thymocyte precursors to incorporate the analogue BrdU was used as a measure of intrathymic proliferation. The number of cells in S phase of the cell cycle was analyzed after a single injection of BrdU (Fig. 2 A). Only a fraction of the immature thymocytes are labeled under these conditions, and it is clear that T cell precursors in γc− mice show defects in proliferation, as both CD44+CD25− and CD44+CD25+ cells have markedly reduced BrdU incorporation relative to their γc+ counterparts (the CD44−CD25+ and CD44−CD25− subsets were not analyzed in γc− thymi due to their extremely small absolute numbers; these subsets were normally labeled in γc+ controls [data not shown]). DP cells from γc− mice were similarly affected.

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