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Bad can act as a key regulator of T cell apoptosis and T cell development.

Mok CL, Gil-Gómez G, Williams O, Coles M, Taga S, Tolaini M, Norton T, Kioussis D, Brady HJ - J. Exp. Med. (1999)

Bottom Line: Here, we show that Bad expression levels are greatly increased in thymocytes during apoptosis.The numbers of T cells are greatly depleted and the processes of T cell development and selection are perturbed.These data suggest that Bad can act as a key regulator of T cell apoptosis and that this is a consequence of its upregulation after exposure to death stimuli.

View Article: PubMed Central - PubMed

Affiliation: Division of Molecular Immunology, MRC National Institute for Medical Research, London NW7 1AA, United Kingdom.

ABSTRACT
Bad is a distant relative of Bcl-2 and acts to promote cell death. Here, we show that Bad expression levels are greatly increased in thymocytes during apoptosis. We generated bad transgenic mice to study the action of upregulated Bad expression on T cell apoptosis. The T cells from these mice are highly sensitive to apoptotic stimuli, including anti-CD95. The numbers of T cells are greatly depleted and the processes of T cell development and selection are perturbed. We show that the proapoptotic function of Bad in primary T cells is regulated by Akt kinase and that Bad overexpression enhances both cell cycle progression and interleukin 2 production after T cell activation. These data suggest that Bad can act as a key regulator of T cell apoptosis and that this is a consequence of its upregulation after exposure to death stimuli.

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bad transgenic mice exhibit increased levels of apoptosis. (A) Total thymocytes from bad and nontransgenic (WT) littermates were cultured  in vitro for 6 h. Duplicate samples were analyzed from each mouse at each time point indicated. Each value represents the mean ± range of the duplicate  determinations. Two individual mice per phenotype are represented. The (+) indicates the presence of the apoptotic stimulus and the (−) indicates its  absence. The numbers 1 and 3 refer to mice from the independent bad transgenic lines 1 and 3, respectively. Similar studies were carried out after treatment  with either (B) 5 Gy γ-irradiation, (C) 5 μM dexamethasone, or (D) anti-CD95 antibody, together with untreated controls. Similar results were obtained  in three independent experiments.
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Figure 4: bad transgenic mice exhibit increased levels of apoptosis. (A) Total thymocytes from bad and nontransgenic (WT) littermates were cultured in vitro for 6 h. Duplicate samples were analyzed from each mouse at each time point indicated. Each value represents the mean ± range of the duplicate determinations. Two individual mice per phenotype are represented. The (+) indicates the presence of the apoptotic stimulus and the (−) indicates its absence. The numbers 1 and 3 refer to mice from the independent bad transgenic lines 1 and 3, respectively. Similar studies were carried out after treatment with either (B) 5 Gy γ-irradiation, (C) 5 μM dexamethasone, or (D) anti-CD95 antibody, together with untreated controls. Similar results were obtained in three independent experiments.

Mentions: We investigated the effect of bad overexpression in response to apoptotic stimuli in T cells from bad transgenic mice. We used several stimuli that have been shown to induce apoptotic cell death. These included stimuli blocked by Bcl-2, i.e., γ-radiation and dexamethasone as well as CD95-induced apoptosis which is not blocked by Bcl-2 but can be blocked by Bcl-xL (33, 34). Thymocytes from bad transgenic mice and nontransgenic littermates were treated with apoptotic stimuli, samples harvested at various time points, and the amount of apoptosis determined by propidium iodide staining of DNA followed by flow cytometry analysis (26). Previous studies have shown that overexpression of Bad alone in a cell line has no effect on apoptosis (14). However, we show that thymocytes from bad transgenic mice placed in culture have significantly increased levels of apoptosis by as early as 4 h (Fig. 4 A). After 6 h of incubation there is >10-fold increase in the proportion of cells undergoing apoptosis compared with the nontransgenic mice. Therefore, overexpression of bad alone is able to greatly accelerate the rate of apoptosis of thymocytes in culture.


Bad can act as a key regulator of T cell apoptosis and T cell development.

Mok CL, Gil-Gómez G, Williams O, Coles M, Taga S, Tolaini M, Norton T, Kioussis D, Brady HJ - J. Exp. Med. (1999)

bad transgenic mice exhibit increased levels of apoptosis. (A) Total thymocytes from bad and nontransgenic (WT) littermates were cultured  in vitro for 6 h. Duplicate samples were analyzed from each mouse at each time point indicated. Each value represents the mean ± range of the duplicate  determinations. Two individual mice per phenotype are represented. The (+) indicates the presence of the apoptotic stimulus and the (−) indicates its  absence. The numbers 1 and 3 refer to mice from the independent bad transgenic lines 1 and 3, respectively. Similar studies were carried out after treatment  with either (B) 5 Gy γ-irradiation, (C) 5 μM dexamethasone, or (D) anti-CD95 antibody, together with untreated controls. Similar results were obtained  in three independent experiments.
© Copyright Policy
Related In: Results  -  Collection

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Figure 4: bad transgenic mice exhibit increased levels of apoptosis. (A) Total thymocytes from bad and nontransgenic (WT) littermates were cultured in vitro for 6 h. Duplicate samples were analyzed from each mouse at each time point indicated. Each value represents the mean ± range of the duplicate determinations. Two individual mice per phenotype are represented. The (+) indicates the presence of the apoptotic stimulus and the (−) indicates its absence. The numbers 1 and 3 refer to mice from the independent bad transgenic lines 1 and 3, respectively. Similar studies were carried out after treatment with either (B) 5 Gy γ-irradiation, (C) 5 μM dexamethasone, or (D) anti-CD95 antibody, together with untreated controls. Similar results were obtained in three independent experiments.
Mentions: We investigated the effect of bad overexpression in response to apoptotic stimuli in T cells from bad transgenic mice. We used several stimuli that have been shown to induce apoptotic cell death. These included stimuli blocked by Bcl-2, i.e., γ-radiation and dexamethasone as well as CD95-induced apoptosis which is not blocked by Bcl-2 but can be blocked by Bcl-xL (33, 34). Thymocytes from bad transgenic mice and nontransgenic littermates were treated with apoptotic stimuli, samples harvested at various time points, and the amount of apoptosis determined by propidium iodide staining of DNA followed by flow cytometry analysis (26). Previous studies have shown that overexpression of Bad alone in a cell line has no effect on apoptosis (14). However, we show that thymocytes from bad transgenic mice placed in culture have significantly increased levels of apoptosis by as early as 4 h (Fig. 4 A). After 6 h of incubation there is >10-fold increase in the proportion of cells undergoing apoptosis compared with the nontransgenic mice. Therefore, overexpression of bad alone is able to greatly accelerate the rate of apoptosis of thymocytes in culture.

Bottom Line: Here, we show that Bad expression levels are greatly increased in thymocytes during apoptosis.The numbers of T cells are greatly depleted and the processes of T cell development and selection are perturbed.These data suggest that Bad can act as a key regulator of T cell apoptosis and that this is a consequence of its upregulation after exposure to death stimuli.

View Article: PubMed Central - PubMed

Affiliation: Division of Molecular Immunology, MRC National Institute for Medical Research, London NW7 1AA, United Kingdom.

ABSTRACT
Bad is a distant relative of Bcl-2 and acts to promote cell death. Here, we show that Bad expression levels are greatly increased in thymocytes during apoptosis. We generated bad transgenic mice to study the action of upregulated Bad expression on T cell apoptosis. The T cells from these mice are highly sensitive to apoptotic stimuli, including anti-CD95. The numbers of T cells are greatly depleted and the processes of T cell development and selection are perturbed. We show that the proapoptotic function of Bad in primary T cells is regulated by Akt kinase and that Bad overexpression enhances both cell cycle progression and interleukin 2 production after T cell activation. These data suggest that Bad can act as a key regulator of T cell apoptosis and that this is a consequence of its upregulation after exposure to death stimuli.

Show MeSH
Related in: MedlinePlus