Limits...
T cell-specific ablation of Fas leads to Fas ligand-mediated lymphocyte depletion and inflammatory pulmonary fibrosis.

Hao Z, Hampel B, Yagita H, Rajewsky K - J. Exp. Med. (2004)

Bottom Line: Experiments in which Fas was ablated in T cells, B cells, T and B cells, or in a more generalized manner demonstrated that the development of lymphoproliferative disease as seen in Fas-deficient mice requires Fas ablation in lymphoid and nonlymphoid tissues.In addition, the mutant animals developed a fatal wasting syndrome caused by massive leukocyte infiltration in the lungs together with increased inflammatory cytokine production and pulmonary fibrosis.Thus, FasL-mediated interaction of activated, Fas-deficient T cells with Fas-expressing cells in their environment leads to break down of lymphocyte homeostasis and development of a lung disease strikingly resembling idiopathic pulmonary fibrosis in humans, a common and severe disease for which the mutant mice may serve as a first animal model.

View Article: PubMed Central - PubMed

Affiliation: 620 University Ave., Toronto, ON, M5G 2C1, Canada. zyhao@uhnres.utoronto.ca

ABSTRACT
To study the role of Fas-Fas ligand (FasL) interaction-mediated apoptosis in lymphocyte homeostasis, we generated a mutant fas allele allowing conditional inactivation of the fas gene through Cre-mediated recombination. Experiments in which Fas was ablated in T cells, B cells, T and B cells, or in a more generalized manner demonstrated that the development of lymphoproliferative disease as seen in Fas-deficient mice requires Fas ablation in lymphoid and nonlymphoid tissues. Selective inactivation of Fas in T cells led to a severe lymphopenia over time, accompanied by up-regulation of FasL on activated T cells and apoptosis of peripheral lymphocytes. In addition, the mutant animals developed a fatal wasting syndrome caused by massive leukocyte infiltration in the lungs together with increased inflammatory cytokine production and pulmonary fibrosis. Inhibition of Fas-FasL interaction in vivo completely prevented the loss of lymphocytes and initial lymphocyte infiltration in the lungs. Thus, FasL-mediated interaction of activated, Fas-deficient T cells with Fas-expressing cells in their environment leads to break down of lymphocyte homeostasis and development of a lung disease strikingly resembling idiopathic pulmonary fibrosis in humans, a common and severe disease for which the mutant mice may serve as a first animal model.

Show MeSH

Related in: MedlinePlus

Activation and high levels of FasL expression in Fas-deficient T cells. (a) Expression of the activation marker CD69 on splenic CD3+ T cells. (b) Analysis of CD62L versus CD44 on gated CD4+ splenic cells to determine the proportion of naive (CD62Lhigh/CD44low) and activated/memory (CD62Llow/CD44high) T cells. (c) FasL expression on gated CD3+ or CD3+CD69+ LN cells from 5-mo-old animals. (d) Active caspase-3 activity in T and B cells of LN cells from 18-wk-old mice. Three to five mice per group were analyzed, and a representative analysis is shown for each group.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2211818&req=5

fig4: Activation and high levels of FasL expression in Fas-deficient T cells. (a) Expression of the activation marker CD69 on splenic CD3+ T cells. (b) Analysis of CD62L versus CD44 on gated CD4+ splenic cells to determine the proportion of naive (CD62Lhigh/CD44low) and activated/memory (CD62Llow/CD44high) T cells. (c) FasL expression on gated CD3+ or CD3+CD69+ LN cells from 5-mo-old animals. (d) Active caspase-3 activity in T and B cells of LN cells from 18-wk-old mice. Three to five mice per group were analyzed, and a representative analysis is shown for each group.

Mentions: Approximately 50% of the peripheral T cells in the T cell–specific Fas KO mice developed an activated phenotype as was evident from the up-regulation of CD69 at the age of 5 mo, but not 2 mo (Fig. 4 a). Likewise, the proportions of CD62Lhigh/CD44low naive and CD62Llow/CD44high activated/memory T cells among the CD4 population in the mutants were comparable to those in the controls at the age of 2 mo, but an increase of the fraction of activated/memory T cells became evident at the age of 5 mo. At 7 mo, there were almost no naive T cells in the spleens of the mutant mice, and 91% of the T cells were activated/memory cells (Fig. 4 b). A similar trend was also seen in the case of CD8 T cells, but it was less dramatic (unpublished data). In parallel, activated T cells from T cell–specific Fas KO mice expressed very high levels of FasL that were far beyond those on T cells from fasdel/del mice at the age of 5 mo, but not 2 mo (Fig. 4 c and not depicted). Notably, the loss of lymphocytes in the secondary lymphoid organs correlated with increasing T cell activation. Although not explaining the loss of naive T cells, it appeared possible that the activated T cells appearing in the animals were directly causing the loss of B cells through Fas–FasL interaction. To obtain evidence in this direction, we analyzed the lymphocytes in the mutant animals for the presence of active (cleaved) caspase-3, a marker for cells undergoing apoptosis upon death receptor engagement or stress-induced cytochrome c release (2). As shown in Fig. 4 d, ∼40% of B cells, but no T cells, from the LNs of the mutants indeed displayed caspase-3 activity.


T cell-specific ablation of Fas leads to Fas ligand-mediated lymphocyte depletion and inflammatory pulmonary fibrosis.

Hao Z, Hampel B, Yagita H, Rajewsky K - J. Exp. Med. (2004)

Activation and high levels of FasL expression in Fas-deficient T cells. (a) Expression of the activation marker CD69 on splenic CD3+ T cells. (b) Analysis of CD62L versus CD44 on gated CD4+ splenic cells to determine the proportion of naive (CD62Lhigh/CD44low) and activated/memory (CD62Llow/CD44high) T cells. (c) FasL expression on gated CD3+ or CD3+CD69+ LN cells from 5-mo-old animals. (d) Active caspase-3 activity in T and B cells of LN cells from 18-wk-old mice. Three to five mice per group were analyzed, and a representative analysis is shown for each group.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2211818&req=5

fig4: Activation and high levels of FasL expression in Fas-deficient T cells. (a) Expression of the activation marker CD69 on splenic CD3+ T cells. (b) Analysis of CD62L versus CD44 on gated CD4+ splenic cells to determine the proportion of naive (CD62Lhigh/CD44low) and activated/memory (CD62Llow/CD44high) T cells. (c) FasL expression on gated CD3+ or CD3+CD69+ LN cells from 5-mo-old animals. (d) Active caspase-3 activity in T and B cells of LN cells from 18-wk-old mice. Three to five mice per group were analyzed, and a representative analysis is shown for each group.
Mentions: Approximately 50% of the peripheral T cells in the T cell–specific Fas KO mice developed an activated phenotype as was evident from the up-regulation of CD69 at the age of 5 mo, but not 2 mo (Fig. 4 a). Likewise, the proportions of CD62Lhigh/CD44low naive and CD62Llow/CD44high activated/memory T cells among the CD4 population in the mutants were comparable to those in the controls at the age of 2 mo, but an increase of the fraction of activated/memory T cells became evident at the age of 5 mo. At 7 mo, there were almost no naive T cells in the spleens of the mutant mice, and 91% of the T cells were activated/memory cells (Fig. 4 b). A similar trend was also seen in the case of CD8 T cells, but it was less dramatic (unpublished data). In parallel, activated T cells from T cell–specific Fas KO mice expressed very high levels of FasL that were far beyond those on T cells from fasdel/del mice at the age of 5 mo, but not 2 mo (Fig. 4 c and not depicted). Notably, the loss of lymphocytes in the secondary lymphoid organs correlated with increasing T cell activation. Although not explaining the loss of naive T cells, it appeared possible that the activated T cells appearing in the animals were directly causing the loss of B cells through Fas–FasL interaction. To obtain evidence in this direction, we analyzed the lymphocytes in the mutant animals for the presence of active (cleaved) caspase-3, a marker for cells undergoing apoptosis upon death receptor engagement or stress-induced cytochrome c release (2). As shown in Fig. 4 d, ∼40% of B cells, but no T cells, from the LNs of the mutants indeed displayed caspase-3 activity.

Bottom Line: Experiments in which Fas was ablated in T cells, B cells, T and B cells, or in a more generalized manner demonstrated that the development of lymphoproliferative disease as seen in Fas-deficient mice requires Fas ablation in lymphoid and nonlymphoid tissues.In addition, the mutant animals developed a fatal wasting syndrome caused by massive leukocyte infiltration in the lungs together with increased inflammatory cytokine production and pulmonary fibrosis.Thus, FasL-mediated interaction of activated, Fas-deficient T cells with Fas-expressing cells in their environment leads to break down of lymphocyte homeostasis and development of a lung disease strikingly resembling idiopathic pulmonary fibrosis in humans, a common and severe disease for which the mutant mice may serve as a first animal model.

View Article: PubMed Central - PubMed

Affiliation: 620 University Ave., Toronto, ON, M5G 2C1, Canada. zyhao@uhnres.utoronto.ca

ABSTRACT
To study the role of Fas-Fas ligand (FasL) interaction-mediated apoptosis in lymphocyte homeostasis, we generated a mutant fas allele allowing conditional inactivation of the fas gene through Cre-mediated recombination. Experiments in which Fas was ablated in T cells, B cells, T and B cells, or in a more generalized manner demonstrated that the development of lymphoproliferative disease as seen in Fas-deficient mice requires Fas ablation in lymphoid and nonlymphoid tissues. Selective inactivation of Fas in T cells led to a severe lymphopenia over time, accompanied by up-regulation of FasL on activated T cells and apoptosis of peripheral lymphocytes. In addition, the mutant animals developed a fatal wasting syndrome caused by massive leukocyte infiltration in the lungs together with increased inflammatory cytokine production and pulmonary fibrosis. Inhibition of Fas-FasL interaction in vivo completely prevented the loss of lymphocytes and initial lymphocyte infiltration in the lungs. Thus, FasL-mediated interaction of activated, Fas-deficient T cells with Fas-expressing cells in their environment leads to break down of lymphocyte homeostasis and development of a lung disease strikingly resembling idiopathic pulmonary fibrosis in humans, a common and severe disease for which the mutant mice may serve as a first animal model.

Show MeSH
Related in: MedlinePlus