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The common cytokine receptor gamma chain plays an essential role in regulating lymphoid homeostasis.

Nakajima H, Shores EW, Noguchi M, Leonard WJ - J. Exp. Med. (1997)

Bottom Line: Although the manner in which these diverse events are coordinated is incompletely understood, cytokines are known to play major roles.Whereas IL-7 is essential for lymphoid development, IL-2 and IL-4 are vital for lymphocyte proliferation.However, because the CD4+ T cells accumulate, it is clear that the rate of proliferation exceeds the rate of cell death.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Molecular Immunology, National Heart, Lung, and Blood Institute, Bethesda, Maryland 20892, USA.

ABSTRACT
In the immune system, there is a careful regulation not only of lymphoid development and proliferation, but also of the fate of activated and proliferating cells. Although the manner in which these diverse events are coordinated is incompletely understood, cytokines are known to play major roles. Whereas IL-7 is essential for lymphoid development, IL-2 and IL-4 are vital for lymphocyte proliferation. The receptors for each of these cytokines contain the common cytokine receptor gamma chain (gammac), and it was previously shown that gammac-deficient mice exhibit severely compromised development and responsiveness to IL-2, IL-4, and IL-7. Nevertheless, these mice exhibit an age-dependent accumulation of splenic CD4+ T cells, the majority of which have a phenotype typical of memory/activated cells. When gammac-deficient mice were mated to DO11.10 T cell receptor (TCR) transgenic mice, only the T cells bearing endogenous TCRs had this phenotype, suggesting that its acquisition was TCR dependent. Not only do the CD4+ T cells from gammac-deficient mice exhibit an activated phenotype and greatly enhanced incorporation of bromodeoxyuridine but, consistent with the lack of gammac-dependent survival signals, they also exhibit an augmented rate of apoptosis. However, because the CD4+ T cells accumulate, it is clear that the rate of proliferation exceeds the rate of cell death. Thus, surprisingly, although gammac-independent signals are sufficient to mediate expansion of CD4+ T cells in these mice, gammac-dependent signals are required to regulate the fate of activated CD4+ T cells, underscoring the importance of gammac-dependent signals in controlling lymphoid homeo-stasis.

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Augmented cell death and diminished Bcl-2 expression in  γc-deficient CD4+ T cells. (A) Spontaneous cell death in vitro. Purified  splenic CD4+ T cells from 6-wk-old mice were cultured in RPMI medium containing 10% charcoal-treated fetal bovine serum (Cocalico Biological, Inc.) for 8–48 h, harvested, and cell survival determined by staining with 5 μg/ml of PI, followed by analysis using a FACSort®. Data for  each mouse were analyzed in duplicate. Shown are the means ± SD of  three mice in each group. At time 0, approximately 98% of cells from  wild-type and 93% of cells from γc-deficient mice were PI negative. (B)  Annexin V binding to CD4+ T cells. Splenocytes from 6-wk-old mice  were stained with anti-CD4 Cy-Chrome and then with annexin V FITC.  Annexin V binding (log scale) is shown for CD4+ PI− cells. (C) Bcl-2 expression in splenic CD4+ T cells was analyzed approximately as previously described (14). The histograms show profiles for staining with anti-Bcl-2  (closed histograms) and control IgG (open histograms) in wild-type and γc-deficient mice (log scale).
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Figure 2: Augmented cell death and diminished Bcl-2 expression in γc-deficient CD4+ T cells. (A) Spontaneous cell death in vitro. Purified splenic CD4+ T cells from 6-wk-old mice were cultured in RPMI medium containing 10% charcoal-treated fetal bovine serum (Cocalico Biological, Inc.) for 8–48 h, harvested, and cell survival determined by staining with 5 μg/ml of PI, followed by analysis using a FACSort®. Data for each mouse were analyzed in duplicate. Shown are the means ± SD of three mice in each group. At time 0, approximately 98% of cells from wild-type and 93% of cells from γc-deficient mice were PI negative. (B) Annexin V binding to CD4+ T cells. Splenocytes from 6-wk-old mice were stained with anti-CD4 Cy-Chrome and then with annexin V FITC. Annexin V binding (log scale) is shown for CD4+ PI− cells. (C) Bcl-2 expression in splenic CD4+ T cells was analyzed approximately as previously described (14). The histograms show profiles for staining with anti-Bcl-2 (closed histograms) and control IgG (open histograms) in wild-type and γc-deficient mice (log scale).

Mentions: Based on the BrdU uptake studies, the γc-deficient mice had an apparent replication rate much greater than wildtype mice (21.43%/d for γc-deficient mice and 6.32%/d for wild-type mice; see Materials and Methods). Such an increased rate for the γc-deficient mice should have yielded a much greater accumulation of cells than actually seen (Fig. 1 A), suggesting that CD4+ T cells from the γc-deficient mice had an increased rate of cell death (see Materials and Methods). Indeed, when cultured without stimulation, purified splenic CD4+ T cells from γc-deficient mice exhibited a higher level of death than cells from wild-type mice, with the greatest difference occurring in the first 8 h (Fig. 2 A). Increased apoptosis was confirmed both by TUNEL analysis (data not shown) and by staining with annexin V (Fig. 2 B), which allows the detection of apoptotic cells at an early stage because of its selective affinity for phospholipids, especially phosphatidylserine (PS), which is exposed on the cell surface in apoptotic cells, while normally PS is restricted to the inner cell membrane (20–22). The rapid increase in death seen at 8 h in γc-deficient mice (Fig. 2 A) presumably is accounted for by the large number of cells that stained with annexin V at time 0 (Fig. 2 B), suggesting that splenic CD4+ T cells of γc-deficient mice may be primed to die by apoptosis in vivo. Bcl-2 levels correlate with the survival of lymphoid cells (23, 24) and are induced by γc-dependent cytokines that protect against apoptosis (25–28). Therefore, it was interesting that γc-deficient splenic CD4+ T cells expressed very low levels of Bcl-2 (Fig. 2 C) (including both CD62Lhigh and CD62Llow subpopulations; data not shown), suggesting that γc is required for maintaining the normal levels of Bcl-2 expression in both activated and naive peripheral CD4+ T cells.


The common cytokine receptor gamma chain plays an essential role in regulating lymphoid homeostasis.

Nakajima H, Shores EW, Noguchi M, Leonard WJ - J. Exp. Med. (1997)

Augmented cell death and diminished Bcl-2 expression in  γc-deficient CD4+ T cells. (A) Spontaneous cell death in vitro. Purified  splenic CD4+ T cells from 6-wk-old mice were cultured in RPMI medium containing 10% charcoal-treated fetal bovine serum (Cocalico Biological, Inc.) for 8–48 h, harvested, and cell survival determined by staining with 5 μg/ml of PI, followed by analysis using a FACSort®. Data for  each mouse were analyzed in duplicate. Shown are the means ± SD of  three mice in each group. At time 0, approximately 98% of cells from  wild-type and 93% of cells from γc-deficient mice were PI negative. (B)  Annexin V binding to CD4+ T cells. Splenocytes from 6-wk-old mice  were stained with anti-CD4 Cy-Chrome and then with annexin V FITC.  Annexin V binding (log scale) is shown for CD4+ PI− cells. (C) Bcl-2 expression in splenic CD4+ T cells was analyzed approximately as previously described (14). The histograms show profiles for staining with anti-Bcl-2  (closed histograms) and control IgG (open histograms) in wild-type and γc-deficient mice (log scale).
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Figure 2: Augmented cell death and diminished Bcl-2 expression in γc-deficient CD4+ T cells. (A) Spontaneous cell death in vitro. Purified splenic CD4+ T cells from 6-wk-old mice were cultured in RPMI medium containing 10% charcoal-treated fetal bovine serum (Cocalico Biological, Inc.) for 8–48 h, harvested, and cell survival determined by staining with 5 μg/ml of PI, followed by analysis using a FACSort®. Data for each mouse were analyzed in duplicate. Shown are the means ± SD of three mice in each group. At time 0, approximately 98% of cells from wild-type and 93% of cells from γc-deficient mice were PI negative. (B) Annexin V binding to CD4+ T cells. Splenocytes from 6-wk-old mice were stained with anti-CD4 Cy-Chrome and then with annexin V FITC. Annexin V binding (log scale) is shown for CD4+ PI− cells. (C) Bcl-2 expression in splenic CD4+ T cells was analyzed approximately as previously described (14). The histograms show profiles for staining with anti-Bcl-2 (closed histograms) and control IgG (open histograms) in wild-type and γc-deficient mice (log scale).
Mentions: Based on the BrdU uptake studies, the γc-deficient mice had an apparent replication rate much greater than wildtype mice (21.43%/d for γc-deficient mice and 6.32%/d for wild-type mice; see Materials and Methods). Such an increased rate for the γc-deficient mice should have yielded a much greater accumulation of cells than actually seen (Fig. 1 A), suggesting that CD4+ T cells from the γc-deficient mice had an increased rate of cell death (see Materials and Methods). Indeed, when cultured without stimulation, purified splenic CD4+ T cells from γc-deficient mice exhibited a higher level of death than cells from wild-type mice, with the greatest difference occurring in the first 8 h (Fig. 2 A). Increased apoptosis was confirmed both by TUNEL analysis (data not shown) and by staining with annexin V (Fig. 2 B), which allows the detection of apoptotic cells at an early stage because of its selective affinity for phospholipids, especially phosphatidylserine (PS), which is exposed on the cell surface in apoptotic cells, while normally PS is restricted to the inner cell membrane (20–22). The rapid increase in death seen at 8 h in γc-deficient mice (Fig. 2 A) presumably is accounted for by the large number of cells that stained with annexin V at time 0 (Fig. 2 B), suggesting that splenic CD4+ T cells of γc-deficient mice may be primed to die by apoptosis in vivo. Bcl-2 levels correlate with the survival of lymphoid cells (23, 24) and are induced by γc-dependent cytokines that protect against apoptosis (25–28). Therefore, it was interesting that γc-deficient splenic CD4+ T cells expressed very low levels of Bcl-2 (Fig. 2 C) (including both CD62Lhigh and CD62Llow subpopulations; data not shown), suggesting that γc is required for maintaining the normal levels of Bcl-2 expression in both activated and naive peripheral CD4+ T cells.

Bottom Line: Although the manner in which these diverse events are coordinated is incompletely understood, cytokines are known to play major roles.Whereas IL-7 is essential for lymphoid development, IL-2 and IL-4 are vital for lymphocyte proliferation.However, because the CD4+ T cells accumulate, it is clear that the rate of proliferation exceeds the rate of cell death.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Molecular Immunology, National Heart, Lung, and Blood Institute, Bethesda, Maryland 20892, USA.

ABSTRACT
In the immune system, there is a careful regulation not only of lymphoid development and proliferation, but also of the fate of activated and proliferating cells. Although the manner in which these diverse events are coordinated is incompletely understood, cytokines are known to play major roles. Whereas IL-7 is essential for lymphoid development, IL-2 and IL-4 are vital for lymphocyte proliferation. The receptors for each of these cytokines contain the common cytokine receptor gamma chain (gammac), and it was previously shown that gammac-deficient mice exhibit severely compromised development and responsiveness to IL-2, IL-4, and IL-7. Nevertheless, these mice exhibit an age-dependent accumulation of splenic CD4+ T cells, the majority of which have a phenotype typical of memory/activated cells. When gammac-deficient mice were mated to DO11.10 T cell receptor (TCR) transgenic mice, only the T cells bearing endogenous TCRs had this phenotype, suggesting that its acquisition was TCR dependent. Not only do the CD4+ T cells from gammac-deficient mice exhibit an activated phenotype and greatly enhanced incorporation of bromodeoxyuridine but, consistent with the lack of gammac-dependent survival signals, they also exhibit an augmented rate of apoptosis. However, because the CD4+ T cells accumulate, it is clear that the rate of proliferation exceeds the rate of cell death. Thus, surprisingly, although gammac-independent signals are sufficient to mediate expansion of CD4+ T cells in these mice, gammac-dependent signals are required to regulate the fate of activated CD4+ T cells, underscoring the importance of gammac-dependent signals in controlling lymphoid homeo-stasis.

Show MeSH
Related in: MedlinePlus