Metabolites from apoptotic thymocytes inhibit thymopoiesis in adenosine deaminase–deficient fetal thymic organ cultures

Thompson, Linda F.; Wiele, C. Justin Van De; Laurent, Aletha B.; Hooker, Scott W.; Vaughn, James G.; Jiang, Hong; Khare, K. C.; Kellems, Rodney E.; Blackburn, Michael R.; Hershfield, Michael S.; Resta, Regina

doi:10.1172/jci9944

Cited by 35 publications

(40 citation statements)

References 39 publications

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“…An investigation of the B cell compartment in the bone marrow of ADA-deficient mice was initiated to determine whether, in analogy to T cell development, a blockade in B cell lymphopoiesis exists (5,16,17). The developmental parallels showed by B and T cells, including gene rearrangement and selection, suggested that ADA deficiency, with a block in early T cell development, could equally affect the early B cell maturation program.…”

Section: B Cell Development In Bone Marrow Is Not Impaired In Ada-defmentioning

confidence: 99%

Impaired Germinal Center Maturation in Adenosine Deaminase Deficiency

Aldrich

Chen

Blackburn

et al. 2003

The Journal of Immunology

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Mice deficient in the enzyme adenosine deaminase (ADA) have small lymphoid organs that contain reduced numbers of peripheral lymphocytes, and they are immunodeficient. We investigated B cell deficiency in ADA-deficient mice and found that B cell development in the bone marrow was normal. However, spleens were markedly smaller, their architecture was dramatically altered, and splenic B lymphocytes showed defects in proliferation and activation. ADA-deficient B cells exhibited a higher propensity to undergo B cell receptor-mediated apoptosis than their wild-type counterparts, suggesting that ADA plays a role in the survival of cells during Ag-dependent responses. In keeping with this finding, IgM production by extrafollicular plasmablast cells was higher in ADA-deficient than in wild-type mice, thus indicating that activated B cells accumulate extrafollicularly as a result of a poor or nonexistent germinal center formation. This hypothesis was subsequently confirmed by the profound loss of germinal center architecture. A comparison of levels of the ADA substrates, adenosine and 2′-deoxyadenosine, as well resulting dATP levels and S-adenosylhomocysteine hydrolase inhibition in bone marrow and spleen suggested that dATP accumulation in ADA-deficient spleens may be responsible for impaired B cell development. The altered splenic environment and signaling abnormalities may concurrently contribute to a block in B cell Ag-dependent maturation in ADA-deficient mouse spleens.

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Section: B Cell Development In Bone Marrow Is Not Impaired In Ada-defmentioning

confidence: 99%

Impaired Germinal Center Maturation in Adenosine Deaminase Deficiency

Aldrich

Chen

Blackburn

et al. 2003

The Journal of Immunology

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“…ADA-deficient murine fetal thymic organ culture (FTOC) is an excellent model of the human disease (12) because it exhibits many biochemical features of ADA-deficient patients, including ADA substrate and dATP accumulation as well as S-adenosylhomocysteine (SAH) hydrolase inhibition. Furthermore, the yield of thymocytes from ADA-deficient cultures is 85-95% less than in control cultures, with thymocyte development becoming progressively more impaired past the CD4 -CD8 -CD25 + CD44 -stage, the point where T cell receptor β (TCRβ) V→DJ gene rearrangements occur.…”

Section: Introductionmentioning

confidence: 99%

Adenosine kinase inhibition promotes survival of fetal adenosine deaminase–deficient thymocytes by blocking dATP accumulation

Wiele

Vaughn

Blackburn³

et al. 2002

J. Clin. Invest.

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IntroductionAdenosine deaminase (ADA) catalyzes the irreversible deamination of adenosine and deoxyadenosine to inosine and deoxyinosine, respectively. Mutations in the ADA gene that result in loss of enzyme activity cause severe combined immunodeficiency (1). Biochemical aberrations due to ADA deficiency have been delineated over the past 30 years, but it is still unclear why loss of this enzyme activity exhibits such profound effects on the immune system (reviewed in ref. 2). Adenosine and deoxyadenosine, the substrates of ADA, are generated in the microenvironment of emerging thymocytes through normal mechanisms of lymphocyte selection. Thymocytes failing developmental checkpoints die and are degraded by thymic macrophages (3) generating adenosine and deoxyadenosine (4, 5). In a normal thymus, ADA catabolizes these metabolites, but in ADA deficiency they accumulate (6, 7) and exert lymphotoxic effects either directly (2) or after conversion to phosphorylated derivatives such as AMP and dATP (2,(8)(9)(10)(11). In an environment where up to 95% of the cells undergo programmed cell death, it is easy to visualize the potential of a cell to accumulate toxic levels of purine metabolites.ADA-deficient murine fetal thymic organ culture (FTOC) is an excellent model of the human disease (12) because it exhibits many biochemical features of ADA-deficient patients, including ADA substrate and dATP accumulation as well as S-adenosylhomocysteine (SAH) hydrolase inhibition. Furthermore, the yield of thymocytes from ADA-deficient cultures is 85-95% less than in control cultures, with thymocyte development becoming progressively more impaired Thymocyte development past the CD4 -CD8 -stage is markedly inhibited in adenosine deaminase-deficient (ADA-deficient) murine fetal thymic organ cultures (FTOCs) due to the accumulation of ADA substrates derived from thymocytes failing developmental checkpoints. Such cultures can be rescued by overexpression of Bcl-2, suggesting that apoptosis is an important component of the mechanism by which ADA deficiency impairs thymocyte development. Consistent with this conclusion, ADA-deficient FTOCs were partially rescued by a rearranged T cell receptor β transgene that permits virtually all thymocytes to pass the β-selection checkpoint. ADA-deficient cultures were also rescued by the adenosine kinase inhibitor 5′-amino-5′-deoxyadenosine (5′A5′dAdo), indicating that the metabolite responsible for the inhibition of thymocyte development is not adenosine or deoxyadenosine, but a phosphorylated derivative of an ADA substrate. Correction of ADA-deficient FTOCs by 5′A5′dAdo correlated with reduced accumulation of dATP, implicating this compound as the toxic metabolite. In ADA-inhibited FTOCs rescued with a Bcl-2 transgene, however, dATP levels were superelevated, suggesting that cells failing positive and negative selection continued to contribute to the accumulation of ADA substrates. Our data are consistent with dATP-induced mitochondrial cytochrome c release followed by apoptosis as the mechanism b...

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“…In the thymus, where the normal process of T cell development results in extensive cell death, extracellular DNA and high levels of deoxynucleoside kinases together create a persistent source of dATP (3). In the absence of ADA, increased intracellular dATP levels interfere with cellular metabolism, promote mitochondrial cytochrome c release, and ultimately cause apoptosis (3)(4)(5). Thus, ADA knockout mice suffer from pronounced T cell defects.…”

mentioning

confidence: 99%

Restoring balance to B cells in ADA deficiency

Prak

2012

J. Clin. Invest.

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It is paradoxical that immunodeficiency disorders are associated with autoimmunity. Adenosine deaminase (ADA) deficiency, a cause of X-linked severe combined immunodeficiency (SCID), is a case in point. In this issue of the JCI, Sauer and colleagues investigate the B cell defects in ADA-deficient patients. They demonstrate that ADA patients receiving enzyme replacement therapy had B cell tolerance checkpoint defects. Remarkably, gene therapy with a retrovirus that expresses ADA resulted in the apparent correction of these defects, with normalization of peripheral B cell autoantibody frequencies. In vitro, agents that either block ADA or overexpress adenosine resulted in altered B cell receptor and TLR signaling. Collectively, these data implicate a B cell-intrinsic mechanism for alterations in B cell tolerance in the setting of partial ADA deficiency that is corrected by gene therapy.

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Metabolites from apoptotic thymocytes inhibit thymopoiesis in adenosine deaminase–deficient fetal thymic organ cultures

Cited by 35 publications

References 39 publications

Impaired Germinal Center Maturation in Adenosine Deaminase Deficiency

Impaired Germinal Center Maturation in Adenosine Deaminase Deficiency

Adenosine kinase inhibition promotes survival of fetal adenosine deaminase–deficient thymocytes by blocking dATP accumulation

Restoring balance to B cells in ADA deficiency

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