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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.

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Prevention of lymphopenia and cell infiltration in the lungs upon application of anti-FasL antibody. Groups of three mutant and three control mice were treated with anti-FasL antibody or isotype-matched hamster IgG1. Two mice from each group were analyzed 8 wk after antibody application, and one mouse from each group was analyzed at 12 wk. (a) FACS® analysis of lymphocytes in inguinal LNs. (b and c) Coimmunostaining of the spleen (b) and lung (c) sections with anti-CD3 (red) and anti-CD19 (blue) antibody. Shown is the analysis of one set of mice treated with antibody for 8 wk. (b and c) Bars, 200 μm.
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fig7: Prevention of lymphopenia and cell infiltration in the lungs upon application of anti-FasL antibody. Groups of three mutant and three control mice were treated with anti-FasL antibody or isotype-matched hamster IgG1. Two mice from each group were analyzed 8 wk after antibody application, and one mouse from each group was analyzed at 12 wk. (a) FACS® analysis of lymphocytes in inguinal LNs. (b and c) Coimmunostaining of the spleen (b) and lung (c) sections with anti-CD3 (red) and anti-CD19 (blue) antibody. Shown is the analysis of one set of mice treated with antibody for 8 wk. (b and c) Bars, 200 μm.

Mentions: Together, our results reveal two major consequences of Fas inactivation selectively in T cells as follows: the loss of peripheral lymphocytes and the development of a fatal inflammatory pulmonary fibrosis. Because it has been reported that the DN (Thy1+B220+CD4−CD8−) T cells from lpr mice are cytotoxic against Fas-expressing cells on the basis of up-regulated FasL expression (32, 33), and the activated T cells from T cell–specific Fas KO mice abundantly expressed FasL on their surface (Fig. 4 c), we reasoned that both the loss of lymphocytes and the pulmonary disease might be due to FasL-mediated interactions of the mutant T cells with Fas-expressing cells in their environment. With respect to lymphocyte loss, the abundant expression of FasL on T cells could lead to the direct killing of the (Fas proficient) B cells, and Fas–FasL interactions could also directly or indirectly be involved in the eventual depletion of T cells in the mutant animals. If this general notion were correct, application of a neutralizing anti-FasL antibody and, hence, inhibition of Fas–FasL interaction should prevent both lymphopenia and pulmonary disease in these mice. Based on the fact that T and B cells were lost rapidly between 2 and 5 mo of age (Fig. 4 a), 14-wk-old fasfl/fl, CD4-cre mice were chosen for treatment with the neutralizing anti-FasL antibody MFL-1/3 (23). LN T cells from the mutant animals expressed high levels of FasL at this age (unpublished data). Fasfl/fl mice either unmanipulated or treated with anti-FasL antibody or fasfl/fl, CD4-cre mice treated with isotype-matched hamster IgG1 served as controls. As shown in Fig. 7 a, loss of T and B cells in the inguinal LNs from two fasfl/fl, CD4-cre mice 8 wk after the initiation of anti-FasL treatment was completely prevented. In a single animal analyzed 12 wk after treatment, the cell number in the inguinal LNs was reduced to half a million, but was increased threefold in the spleen as compared with controls (unpublished data). Substantial numbers of cells resembling those undergoing lymphoproliferation in lpr mice (Thy1+B220+CD4−CD8−) were generated in the anti-FasL antibody-treated mutants (Fig. 7 a). As expected, fasfl/fl, CD4-cre mice treated with isotype-matched IgG1 lost their lymph node cells over the time of treatment. In agreement with these data, immunohistological analysis on the same set of animals showed that the blockade of Fas–FasL interaction in the mutants also largely prevented the alteration of splenic architecture and the development of splenic sclerosis (Fig. 7 b and not depicted). Strikingly, the anti-FasL antibody treatment also blocked lymphocyte infiltration in the lung (Fig. 7 c). Collectively, these results show that the entire pathology developing in the animals lacking Fas on T cells is due to abnormal Fas–FasL interaction, likely reflecting the interaction of the Fas-deficient T cells with Fas-proficient cells in the environment.


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)

Prevention of lymphopenia and cell infiltration in the lungs upon application of anti-FasL antibody. Groups of three mutant and three control mice were treated with anti-FasL antibody or isotype-matched hamster IgG1. Two mice from each group were analyzed 8 wk after antibody application, and one mouse from each group was analyzed at 12 wk. (a) FACS® analysis of lymphocytes in inguinal LNs. (b and c) Coimmunostaining of the spleen (b) and lung (c) sections with anti-CD3 (red) and anti-CD19 (blue) antibody. Shown is the analysis of one set of mice treated with antibody for 8 wk. (b and c) Bars, 200 μm.
© Copyright Policy
Related In: Results  -  Collection

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

fig7: Prevention of lymphopenia and cell infiltration in the lungs upon application of anti-FasL antibody. Groups of three mutant and three control mice were treated with anti-FasL antibody or isotype-matched hamster IgG1. Two mice from each group were analyzed 8 wk after antibody application, and one mouse from each group was analyzed at 12 wk. (a) FACS® analysis of lymphocytes in inguinal LNs. (b and c) Coimmunostaining of the spleen (b) and lung (c) sections with anti-CD3 (red) and anti-CD19 (blue) antibody. Shown is the analysis of one set of mice treated with antibody for 8 wk. (b and c) Bars, 200 μm.
Mentions: Together, our results reveal two major consequences of Fas inactivation selectively in T cells as follows: the loss of peripheral lymphocytes and the development of a fatal inflammatory pulmonary fibrosis. Because it has been reported that the DN (Thy1+B220+CD4−CD8−) T cells from lpr mice are cytotoxic against Fas-expressing cells on the basis of up-regulated FasL expression (32, 33), and the activated T cells from T cell–specific Fas KO mice abundantly expressed FasL on their surface (Fig. 4 c), we reasoned that both the loss of lymphocytes and the pulmonary disease might be due to FasL-mediated interactions of the mutant T cells with Fas-expressing cells in their environment. With respect to lymphocyte loss, the abundant expression of FasL on T cells could lead to the direct killing of the (Fas proficient) B cells, and Fas–FasL interactions could also directly or indirectly be involved in the eventual depletion of T cells in the mutant animals. If this general notion were correct, application of a neutralizing anti-FasL antibody and, hence, inhibition of Fas–FasL interaction should prevent both lymphopenia and pulmonary disease in these mice. Based on the fact that T and B cells were lost rapidly between 2 and 5 mo of age (Fig. 4 a), 14-wk-old fasfl/fl, CD4-cre mice were chosen for treatment with the neutralizing anti-FasL antibody MFL-1/3 (23). LN T cells from the mutant animals expressed high levels of FasL at this age (unpublished data). Fasfl/fl mice either unmanipulated or treated with anti-FasL antibody or fasfl/fl, CD4-cre mice treated with isotype-matched hamster IgG1 served as controls. As shown in Fig. 7 a, loss of T and B cells in the inguinal LNs from two fasfl/fl, CD4-cre mice 8 wk after the initiation of anti-FasL treatment was completely prevented. In a single animal analyzed 12 wk after treatment, the cell number in the inguinal LNs was reduced to half a million, but was increased threefold in the spleen as compared with controls (unpublished data). Substantial numbers of cells resembling those undergoing lymphoproliferation in lpr mice (Thy1+B220+CD4−CD8−) were generated in the anti-FasL antibody-treated mutants (Fig. 7 a). As expected, fasfl/fl, CD4-cre mice treated with isotype-matched IgG1 lost their lymph node cells over the time of treatment. In agreement with these data, immunohistological analysis on the same set of animals showed that the blockade of Fas–FasL interaction in the mutants also largely prevented the alteration of splenic architecture and the development of splenic sclerosis (Fig. 7 b and not depicted). Strikingly, the anti-FasL antibody treatment also blocked lymphocyte infiltration in the lung (Fig. 7 c). Collectively, these results show that the entire pathology developing in the animals lacking Fas on T cells is due to abnormal Fas–FasL interaction, likely reflecting the interaction of the Fas-deficient T cells with Fas-proficient cells in the environment.

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