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Impaired T cell death and lupus-like autoimmunity in T cell-specific adapter protein-deficient mice.

Drappa J, Kamen LA, Chan E, Georgiev M, Ashany D, Marti F, King PD - J. Exp. Med. (2003)

Bottom Line: T cell-specific adaptor protein (TSAd) is a T lineage-restricted signaling adaptor molecule that is thought to participate in the assembly of intracellular signaling complexes in T cells.On the nonautoimmune-prone C57BL/6 genetic background, TSAd deficiency results in hypergammaglobulinemia that affects all immunoglobulin (Ig)G subclasses.These findings illustrate the role of TSAd as a critical regulator of T cell death whose absence promotes systemic autoimmunity.

View Article: PubMed Central - PubMed

Affiliation: Research Division, Hospital for Special Surgery, Weill Medical College and Graduate School of Medical Sciences, Cornell University, New York, NY 10021, USA.

ABSTRACT
T cell-specific adaptor protein (TSAd) is a T lineage-restricted signaling adaptor molecule that is thought to participate in the assembly of intracellular signaling complexes in T cells. Previous studies of TSAd-deficient mice have revealed a role for TSAd in the induction of T cell interleukin 2 secretion and proliferation. We now show that TSAd-deficient mice are susceptible to lupus-like autoimmune disease. On the nonautoimmune-prone C57BL/6 genetic background, TSAd deficiency results in hypergammaglobulinemia that affects all immunoglobulin (Ig)G subclasses. Older C57BL/6 TSAd-deficient mice (1 yr of age) accumulate large numbers of activated T and B cells in spleen, produce autoantibodies against a variety of self-targets including single stranded (ss) and double stranded (ds) DNA, and, in addition, develop glomerulonephritis. We further show that immunization of younger C57BL/6 TSAd-deficient mice (at age 2 mo) with pristane, a recognized nonspecific inflammatory trigger of lupus, results in more severe glomerulonephritis compared with C57BL/6 controls and the production of high titer ss and ds DNA antibodies of the IgG subclass that are not normally produced by C57BL/6 mice in this model. The development of autoimmunity in TSAd-deficient mice is associated with defective T cell death in vivo. These findings illustrate the role of TSAd as a critical regulator of T cell death whose absence promotes systemic autoimmunity.

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Impaired cytokine production by TSAd-deficient T cells in vivo. Control wild-type and TSAd-deficient mice were immunized with SEB. After 24 h, IL-2 and IFN-γ expression in Vβ8+ splenic T cells was determined by intracellular staining and flow cytometry. Filled and open histograms represent isotype control and anticytokine-stained Vβ8+ T cells, respectively. The percentages of cytokine+ Vβ8+ T cells are indicated in parentheses.
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fig9: Impaired cytokine production by TSAd-deficient T cells in vivo. Control wild-type and TSAd-deficient mice were immunized with SEB. After 24 h, IL-2 and IFN-γ expression in Vβ8+ splenic T cells was determined by intracellular staining and flow cytometry. Filled and open histograms represent isotype control and anticytokine-stained Vβ8+ T cells, respectively. The percentages of cytokine+ Vβ8+ T cells are indicated in parentheses.

Mentions: The Fas death receptor pathway has been studied extensively as a major pathway involved in the control of T cell death (19–21). In in vitro studies, TSAd-deficient T cells showed partial resistance to Fas-mediated apoptosis that was not associated with reduced expression of either Fas or Fas ligand (unpublished data). However, the significance of these findings to the impaired T cell death seen in TSAd-deficient mice in vivo is uncertain because recent studies have indicated that superantigen-induced T cell death is Fas independent (22–24). Therefore, to shed light upon possible mechanisms by which TSAd might regulate T cell death, we undertook gene profiling experiments to determine in total which genes are regulated by TSAd in activated T cells. In these experiments we compared gene expression between purified wild-type and TSAd-deficient CD4+ T cells that were either not stimulated or stimulated for 20 h with a CD3 antibody (directed against the TCR complex) plus an antibody against the CD28 T cell costimulatory receptor. To uncover genes that were positively or negatively regulated by TSAd, several filters were placed upon the data derived from these experiments (refer to Materials and Methods). With the use of these filters, we identified a total of 107 genes (out of ∼12,000) that were positively regulated by TSAd in CD4+ T cells (Fig. 8) . In contrast, using the same filters, we did not identify any genes that were negatively regulated by TSAd. Within the group of positively regulated genes, several have been previously ascribed a proapoptotic function in different cell types. These include the transmembrane protein, BAP29 (25), the intracellular chloride channel, CLIC4 (26), the proto-oncogene, c-myc (27), the molecular chaperone, Hsp60 (28), and IFN-γ (29). Furthermore, confirming earlier findings, IL-2 was identified as a major positively regulated TSAd target gene in these experiments. Although IL-2 is known to function as a T cell growth factor in vitro, numerous studies have shown that IL-2 acts only to promote T cell death in vivo (30–34). Thus, impaired induction of IL-2 in vivo could be an important factor accounting for the resistance of TSAd-deficient T cells to apoptotic death. Given these findings, therefore, we sought to verify that TSAd-deficient T cells produce less IL-2 protein in vivo. For this, we examined IL-2 protein levels in Vβ8+ splenic T cells 24 h after immunization of mice with SEB using an intracellular staining technique. As shown in Fig. 9 , TSAd-deficient Vβ8+ T cells synthesized considerably less IL-2 protein (and IFN-γ) in response to SEB as determined in three repeat experiments. In contrast, for the other apoptosis-related genes, we were unable to detect any differences in protein expression despite the changes in mRNA levels (unpublished data). Thus, TSAd-deficient T cells produce less IL-2 in vivo as well as in vitro, which may account for the development of systemic autoimmunity in these animals.


Impaired T cell death and lupus-like autoimmunity in T cell-specific adapter protein-deficient mice.

Drappa J, Kamen LA, Chan E, Georgiev M, Ashany D, Marti F, King PD - J. Exp. Med. (2003)

Impaired cytokine production by TSAd-deficient T cells in vivo. Control wild-type and TSAd-deficient mice were immunized with SEB. After 24 h, IL-2 and IFN-γ expression in Vβ8+ splenic T cells was determined by intracellular staining and flow cytometry. Filled and open histograms represent isotype control and anticytokine-stained Vβ8+ T cells, respectively. The percentages of cytokine+ Vβ8+ T cells are indicated in parentheses.
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Related In: Results  -  Collection

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fig9: Impaired cytokine production by TSAd-deficient T cells in vivo. Control wild-type and TSAd-deficient mice were immunized with SEB. After 24 h, IL-2 and IFN-γ expression in Vβ8+ splenic T cells was determined by intracellular staining and flow cytometry. Filled and open histograms represent isotype control and anticytokine-stained Vβ8+ T cells, respectively. The percentages of cytokine+ Vβ8+ T cells are indicated in parentheses.
Mentions: The Fas death receptor pathway has been studied extensively as a major pathway involved in the control of T cell death (19–21). In in vitro studies, TSAd-deficient T cells showed partial resistance to Fas-mediated apoptosis that was not associated with reduced expression of either Fas or Fas ligand (unpublished data). However, the significance of these findings to the impaired T cell death seen in TSAd-deficient mice in vivo is uncertain because recent studies have indicated that superantigen-induced T cell death is Fas independent (22–24). Therefore, to shed light upon possible mechanisms by which TSAd might regulate T cell death, we undertook gene profiling experiments to determine in total which genes are regulated by TSAd in activated T cells. In these experiments we compared gene expression between purified wild-type and TSAd-deficient CD4+ T cells that were either not stimulated or stimulated for 20 h with a CD3 antibody (directed against the TCR complex) plus an antibody against the CD28 T cell costimulatory receptor. To uncover genes that were positively or negatively regulated by TSAd, several filters were placed upon the data derived from these experiments (refer to Materials and Methods). With the use of these filters, we identified a total of 107 genes (out of ∼12,000) that were positively regulated by TSAd in CD4+ T cells (Fig. 8) . In contrast, using the same filters, we did not identify any genes that were negatively regulated by TSAd. Within the group of positively regulated genes, several have been previously ascribed a proapoptotic function in different cell types. These include the transmembrane protein, BAP29 (25), the intracellular chloride channel, CLIC4 (26), the proto-oncogene, c-myc (27), the molecular chaperone, Hsp60 (28), and IFN-γ (29). Furthermore, confirming earlier findings, IL-2 was identified as a major positively regulated TSAd target gene in these experiments. Although IL-2 is known to function as a T cell growth factor in vitro, numerous studies have shown that IL-2 acts only to promote T cell death in vivo (30–34). Thus, impaired induction of IL-2 in vivo could be an important factor accounting for the resistance of TSAd-deficient T cells to apoptotic death. Given these findings, therefore, we sought to verify that TSAd-deficient T cells produce less IL-2 protein in vivo. For this, we examined IL-2 protein levels in Vβ8+ splenic T cells 24 h after immunization of mice with SEB using an intracellular staining technique. As shown in Fig. 9 , TSAd-deficient Vβ8+ T cells synthesized considerably less IL-2 protein (and IFN-γ) in response to SEB as determined in three repeat experiments. In contrast, for the other apoptosis-related genes, we were unable to detect any differences in protein expression despite the changes in mRNA levels (unpublished data). Thus, TSAd-deficient T cells produce less IL-2 in vivo as well as in vitro, which may account for the development of systemic autoimmunity in these animals.

Bottom Line: T cell-specific adaptor protein (TSAd) is a T lineage-restricted signaling adaptor molecule that is thought to participate in the assembly of intracellular signaling complexes in T cells.On the nonautoimmune-prone C57BL/6 genetic background, TSAd deficiency results in hypergammaglobulinemia that affects all immunoglobulin (Ig)G subclasses.These findings illustrate the role of TSAd as a critical regulator of T cell death whose absence promotes systemic autoimmunity.

View Article: PubMed Central - PubMed

Affiliation: Research Division, Hospital for Special Surgery, Weill Medical College and Graduate School of Medical Sciences, Cornell University, New York, NY 10021, USA.

ABSTRACT
T cell-specific adaptor protein (TSAd) is a T lineage-restricted signaling adaptor molecule that is thought to participate in the assembly of intracellular signaling complexes in T cells. Previous studies of TSAd-deficient mice have revealed a role for TSAd in the induction of T cell interleukin 2 secretion and proliferation. We now show that TSAd-deficient mice are susceptible to lupus-like autoimmune disease. On the nonautoimmune-prone C57BL/6 genetic background, TSAd deficiency results in hypergammaglobulinemia that affects all immunoglobulin (Ig)G subclasses. Older C57BL/6 TSAd-deficient mice (1 yr of age) accumulate large numbers of activated T and B cells in spleen, produce autoantibodies against a variety of self-targets including single stranded (ss) and double stranded (ds) DNA, and, in addition, develop glomerulonephritis. We further show that immunization of younger C57BL/6 TSAd-deficient mice (at age 2 mo) with pristane, a recognized nonspecific inflammatory trigger of lupus, results in more severe glomerulonephritis compared with C57BL/6 controls and the production of high titer ss and ds DNA antibodies of the IgG subclass that are not normally produced by C57BL/6 mice in this model. The development of autoimmunity in TSAd-deficient mice is associated with defective T cell death in vivo. These findings illustrate the role of TSAd as a critical regulator of T cell death whose absence promotes systemic autoimmunity.

Show MeSH
Related in: MedlinePlus