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Mitochondrial basis for immune deficiency. Evidence from purine nucleoside phosphorylase-deficient mice.

Arpaia E, Benveniste P, Di Cristofano A, Gu Y, Dalal I, Kelly S, Hershfield M, Pandolfi PP, Roifman CM, Cohen A - J. Exp. Med. (2000)

Bottom Line: PNP knockout mice exhibit impaired thymocyte differentiation, reduced mitogenic and allogeneic responses, and decreased numbers of maturing thymocytes and peripheral T cells.We propose that the immune deficiency in PNP deficiency is a result of inhibition of mitochondrial DNA repair due to the accumulation of dGTP in the mitochondria.The end result is increased sensitivity of T cells to spontaneous mitochondrial DNA damage, leading to T cell depletion by apoptosis.

View Article: PubMed Central - PubMed

Affiliation: Division of Immunology/Allergy, Department of Paediatrics, Hospital for Sick Children, The University of Toronto, Ontario, Canada.

ABSTRACT
We generated purine nucleoside phosphorylase (PNP)-deficient mice to gain insight into the mechanism of immune deficiency disease associated with PNP deficiency in humans. Similar to the human disease, PNP deficiency in mice causes an immunodeficiency that affects T lymphocytes more severely than B lymphocytes. PNP knockout mice exhibit impaired thymocyte differentiation, reduced mitogenic and allogeneic responses, and decreased numbers of maturing thymocytes and peripheral T cells. T lymphocytes of PNP-deficient mice exhibit increased apoptosis in vivo and higher sensitivity to gamma irradiation in vitro. We propose that the immune deficiency in PNP deficiency is a result of inhibition of mitochondrial DNA repair due to the accumulation of dGTP in the mitochondria. The end result is increased sensitivity of T cells to spontaneous mitochondrial DNA damage, leading to T cell depletion by apoptosis.

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Increased frequency of apoptotic cells in freshly isolated thymocytes in PNP-deficient mice. Three-color analysis of apoptotic thymocyte subpopulations was carried out in freshly isolated thymocytes stained with conjugated fluorescent antibodies against CD4 and CD8, and then stained with conjugated annexin V as described in Materials and Methods. The frequencies of annexin V–positive apoptotic cells in DP, CD4+ (CD4sp), CD8+ (CD8sp), and DN thymocyte subpopulations of PNP−/− and heterozygous littermates are presented. Data from a single experiment representative of five additional experiments with similar results.
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Figure 6: Increased frequency of apoptotic cells in freshly isolated thymocytes in PNP-deficient mice. Three-color analysis of apoptotic thymocyte subpopulations was carried out in freshly isolated thymocytes stained with conjugated fluorescent antibodies against CD4 and CD8, and then stained with conjugated annexin V as described in Materials and Methods. The frequencies of annexin V–positive apoptotic cells in DP, CD4+ (CD4sp), CD8+ (CD8sp), and DN thymocyte subpopulations of PNP−/− and heterozygous littermates are presented. Data from a single experiment representative of five additional experiments with similar results.

Mentions: To examine whether the depletion of DP thymocytes is due to enhanced apoptosis, we analyzed the frequency of apoptotic cells in thymocyte subpopulations from PNP−/− mice and their heterozygous littermates (Fig. 6). Freshly isolated PNP-deficient thymocytes show a twofold increase in the frequency of apoptotic thymocytes, measured by annexin V binding 28, compared with their heterozygous littermates. The frequency of apoptotic cells in the PNP−/− thymocyte subpopulation is inversely related to Bcl2 expression: it is highest at the DP stage (8.7% of total PNP−/− DP cells), lower in SP CD4 and CD8 cells, and absent in immature DN cells.


Mitochondrial basis for immune deficiency. Evidence from purine nucleoside phosphorylase-deficient mice.

Arpaia E, Benveniste P, Di Cristofano A, Gu Y, Dalal I, Kelly S, Hershfield M, Pandolfi PP, Roifman CM, Cohen A - J. Exp. Med. (2000)

Increased frequency of apoptotic cells in freshly isolated thymocytes in PNP-deficient mice. Three-color analysis of apoptotic thymocyte subpopulations was carried out in freshly isolated thymocytes stained with conjugated fluorescent antibodies against CD4 and CD8, and then stained with conjugated annexin V as described in Materials and Methods. The frequencies of annexin V–positive apoptotic cells in DP, CD4+ (CD4sp), CD8+ (CD8sp), and DN thymocyte subpopulations of PNP−/− and heterozygous littermates are presented. Data from a single experiment representative of five additional experiments with similar results.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2193200&req=5

Figure 6: Increased frequency of apoptotic cells in freshly isolated thymocytes in PNP-deficient mice. Three-color analysis of apoptotic thymocyte subpopulations was carried out in freshly isolated thymocytes stained with conjugated fluorescent antibodies against CD4 and CD8, and then stained with conjugated annexin V as described in Materials and Methods. The frequencies of annexin V–positive apoptotic cells in DP, CD4+ (CD4sp), CD8+ (CD8sp), and DN thymocyte subpopulations of PNP−/− and heterozygous littermates are presented. Data from a single experiment representative of five additional experiments with similar results.
Mentions: To examine whether the depletion of DP thymocytes is due to enhanced apoptosis, we analyzed the frequency of apoptotic cells in thymocyte subpopulations from PNP−/− mice and their heterozygous littermates (Fig. 6). Freshly isolated PNP-deficient thymocytes show a twofold increase in the frequency of apoptotic thymocytes, measured by annexin V binding 28, compared with their heterozygous littermates. The frequency of apoptotic cells in the PNP−/− thymocyte subpopulation is inversely related to Bcl2 expression: it is highest at the DP stage (8.7% of total PNP−/− DP cells), lower in SP CD4 and CD8 cells, and absent in immature DN cells.

Bottom Line: PNP knockout mice exhibit impaired thymocyte differentiation, reduced mitogenic and allogeneic responses, and decreased numbers of maturing thymocytes and peripheral T cells.We propose that the immune deficiency in PNP deficiency is a result of inhibition of mitochondrial DNA repair due to the accumulation of dGTP in the mitochondria.The end result is increased sensitivity of T cells to spontaneous mitochondrial DNA damage, leading to T cell depletion by apoptosis.

View Article: PubMed Central - PubMed

Affiliation: Division of Immunology/Allergy, Department of Paediatrics, Hospital for Sick Children, The University of Toronto, Ontario, Canada.

ABSTRACT
We generated purine nucleoside phosphorylase (PNP)-deficient mice to gain insight into the mechanism of immune deficiency disease associated with PNP deficiency in humans. Similar to the human disease, PNP deficiency in mice causes an immunodeficiency that affects T lymphocytes more severely than B lymphocytes. PNP knockout mice exhibit impaired thymocyte differentiation, reduced mitogenic and allogeneic responses, and decreased numbers of maturing thymocytes and peripheral T cells. T lymphocytes of PNP-deficient mice exhibit increased apoptosis in vivo and higher sensitivity to gamma irradiation in vitro. We propose that the immune deficiency in PNP deficiency is a result of inhibition of mitochondrial DNA repair due to the accumulation of dGTP in the mitochondria. The end result is increased sensitivity of T cells to spontaneous mitochondrial DNA damage, leading to T cell depletion by apoptosis.

Show MeSH
Related in: MedlinePlus