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Query: UMLS:C0021051 (immunodeficiency)
 71,517 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Deoxyadenosine and deoxyguanosine are toxic to human lymphoid cells in culture and have been implicated in the pathogenesis of the immunodeficiency states associated with adenosine deaminase and purine nucleoside phosphorylase deficiency, respectively. We have studied the relative incorporation of several labeled nucleosides into DNA and into nucleotide pools to further elucidate the mechanism of deoxyribonucleoside toxicity. In the presence of an inhibitor of adenosine deaminase [erythro-9-(2-hydroxy-3-nonyl)adenine [EHNA], 5 muM], deoxyadenosine (1-50 muM) progressively decreased the incorporation of thymidine, uridine, and deoxyuridine into DNA, but did not affect uridine incorporation into RNA. This decrease in DNA synthesis was associated with increasing dATP and decreasing dCTP pools. Likewise, incubation of cells with deoxyguanosine caused an elevation of dGTP, depletion of dCTP, and inhibition of DNA synthesis. To test the hypothesis that dATP and dGTP accumulation inhibit DNA synthesis by inhibiting the enzyme ribonucleotide reductase, simultaneous rates of incorporation of [(3)H]uridine and [(14)C]thymidine into DNA were measured in the presence of deoxyadenosine plus EHNA or deoxyguanosine, and in the presence of hydroxyurea, a known inhibitor of ribonucleotide reductase. Hydroxyurea (100 muM) and deoxyguanosine (10 muM) decreased the incorporation of [(3)H]uridine but not of [(14)C]thymidine into DNA; both compounds also substantially increased [(3)H]cytidine incorporation into the ribonucleotide pool while reducing incorporation into the deoxyribonucleotide pool. In contrast, deoxyadenosine plus EHNA did not show this differential inhibition of [(3)H]uridine incorporation into DNA, and the alteration in [(3)H]cytidine incorporation into nucleotide pools was less impressive. These data show an association between accumulation of dATP or dGTP and a primary inhibition of DNA synthesis, and they provide support for ribonucleotide reductase inhibition as the mechanism responsible for deoxyguanosine toxicity. Deoxyadenosine toxicity, however, appears to result from another, or perhaps a combination of, molecular event(s).
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PMID:Purinogenic immunodeficiency diseases. Differential effects of deoxyadenosine and deoxyguanosine on DNA synthesis in human T lymphoblasts. 11 1

Deoxyadenosine at low concentrations and in the presence of an inhibitor of adenosine deaminase (adenosine aminohydrolase, EC 3.5.4.4) is markedly toxic to lymphoblast cell lines of T cell origin but does not impair growth of B cell lines. Deoxyguanosine is also more toxic for T lymphoblasts. In the presence of deoxyadenosine or deoxyguanosine, elevation of the corresponding deoxyribonucleoside triphosphate (dATP or dGTP) occurs in T cell, but not in B cell, lines. The addition of deoxycytidine or dipyridamole results in lower dATP and dGTP levels and prevents deoxyribonucleoside toxicity. These findings provide a molecular basis for the immunodeficiency observed in individuals with several inborn errors of purine metabolism.
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PMID:Purinogenic immunodeficiency diseases: selective toxicity of deoxyribonucleosides for T cells. 31 Oct 4

The effect of thymidine and deoxyadenosine on the antiviral and antibacterial effect of zidovudine was studied in human immunodeficiency virus type 1 (HIV-1) Escherichia coli and Salmonella typhimurium. In quantitative assays, 10 micrograms mL-1 thymidine was shown to increase the 50% inhibitory concentration (IC50) of zidovudine for HIV-1 by approximately 100-fold and to reduce zidovudine (1 microM)-induced protection of C8166 cells from 2.04 to 0.18 log syncytial-forming units. Thymidine also antagonized the antibacterial effect of zidovudine for two E. coli and three S. typhimurium species in a dose-dependent manner; 10 micrograms mL-1 of thymidine increased the minimum inhibitory concentration of zidovudine for E. coli strains by 10-40-fold and for S. typhimurium strains by three-fold. Deoxyadenosine reduced the minimum inhibitory concentration of zidovudine against all five bacterial strains but had no effect on the IC50 of zidovudine for HIV-1, nor did it significantly reverse the antagonism of the antibacterial and antiviral activity of thymidine. The induction of the SOS response in E. coli was reversed in a dose-dependent manner by thymidine while the presence of deoxyadenosine increased induction of the SOS response by zidovudine at suboptimal concentrations.
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PMID:The effect of thymidine on the antibacterial and antiviral activity of zidovudine. 135 4

Deoxyadenosine (dAdo) has been recognized as the toxic metabolite in the immunodeficiency disease associated with adenosine deaminase (ADA) deficiency. Under ADA deficient conditions, dAdo accumulates intracellularly as deoxyadenosine triphosphate (dATP) which by interference with ribonucleotide reductase, prevents DNA synthesis. Recently, we and others have demonstrated that in cells rendered ADA deficient by treatment with deoxycoformycin, dAdo affects T-cell activation events which precede DNA synthesis, such as interleukin 2 receptor (IL-2R) expression and IL-2 production. Here we have analyzed interference of dAdo with the early events of T-cell activation. It is shown that dAdo affects the mitogen induced phosphatidyl inositol turnover. Furthermore dAdo interferes with increase of intracellular calcium. Deoxycytidine, although capable of preventing intracellular accumulation of dATP, cannot reverse the functional consequences of dAdo treatment. The ability of a cell to increase its cytoplasmic free Ca2+, as induced by ionomycin, is not affected by dAdo. The exact target for this novel effect of dAdo is at the present unknown.
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PMID:Interference of deoxyadenosine with transmembrane signaling events in human T lymphocytes. 230 14

Severe combined immunodeficiency disease (SCID) in patients with adenosine deaminase (ADA) deficiency is thought to result from increased levels of purine metabolites. We attempted to immunosuppress a patient with ADA deficiency and SCID using a continuous infusion of deoxyadenosine to obtain engraftment of a T cell-depleted haplocompatible parental bone marrow graft. Before administering the drug in vivo, we investigated hematopoietic colony formation in two children with ADA deficiency (including the potential recipient), the obligate heterozygote donor (father), and normal controls using deoxyadenosine and erythro-9-(2-hydroxy-3-nanyl)adenosine (EHNA), and inhibitor of ADA. Deoxyadenosine alone in concentrations as high as 100 microM had no significant affect on erythroid (BFU-E) or myeloid (CFU-c) colony formation. However, in the presence of EHNA there was a significant reduction in BFU-E and CFU-c growth in all subjects and controls. Increasing doses of deoxyadenosine were given to one patient with ADA deficiency and SCID as a continuous 24-hr intravenous infusion. We found that there was a linear relationship between the dose administered and the plasma level; however, doses greater than 100 mg/day were required to increase erythrocyte dATP levels. We were able to raise intracellular dATP levels to more than three times baseline with doses of deoxyadenosine of 200 mg/day. However, there were no significant effects on the absolute lymphocyte counts or the lymphocyte responses to mitogen or alloantigen, and the haploidentical marrow failed to engraft. Our results suggest that the bone marrow of ADA-deficient patients is normal with respect to standard colony formation, that inhibitors of ADA do not adequately model the deficient state, and that the immunodeficiency in ADA deficiency is not proportionately related to either the deoxyadenosine or dATP levels, both of which were significantly elevated at the time of transplantation.
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PMID:Rejection of bone marrow transplant and resistance of alloantigen reactive cells to in vivo deoxyadenosine in adenosine deaminase deficiency. 297 90

Deoxyadenosine (AdR) appears to be central to the molecular events mediating immunodeficiency in children born with adenosine deaminase (ADA) deficiency but it is still uncertain whether lymphotoxicity is due to AdR directly inhibiting transmethylation reactions in which S-adenosylmethionine is the methyl group donor, or is due to phosphorylation of AdR to deoxyadenosine triphosphate (dATP) which then inhibits ribonucleotide reductase or is due to other mechanisms. Using AdR and the ADA inhibitor deoxycoformycin (dCF) and assessing cell viability, nucleoside incorporation into RNA and DNA, as well as measuring deoxyribonucleoside triphosphate (dNTP) concentrations and S-adenosylhomocysteine (SAH) hydrolase activity, we have studied various types of human lymphoid cells and demonstrated in them the relative importance of the above two mechanisms of AdR toxicity. Treatment of normal resting peripheral blood lymphocytes in culture with AdR and dCF resulted in impaired viability. Although elevated dATP levels as well as decreased SAH hydrolase activities were both observed, the failure of a known inhibitor of ribonucleotide reductase (hydroxyurea) to produce toxicity, and the inability of deoxycytidine (CdR) to achieve a rescue effect, point to another mechanism, possibly inhibition of trans-methylation or ATP depletion being the more likely causes of toxicity in resting lymphocytes. The same mechanism may well account for the rapid and severe lymphopenia in patients treated with dCF. On the other hand, in cultured lymphoblasts in the exponential phase of growth. AdR and dCF produced marked inhibition of growth and cell death both in a Thy-ALL line and in a c-ALL line, in the absence of significant inhibition of SAH hydrolase, but with a substantial elevation in dATP concentrations and depressed levels of the other dNTP. Minor toxicity occurred in a proliferating B lymphoblast line despite almost complete inactivation of SAH hydrolase. These observations indicate inhibition of ribonucleotide reductase as the more likely mechanism of toxicity in rapidly proliferating lymphocytes. Other T-cells actively synthesizing DNA, such as PHA-stimulated or MLC activated lymphocytes and T-lymphoid colony forming cells, are also likely to be affected by the same mechanism. Indeed in PHA-stimulated lymphocytes, deoxycytidine caused significant although incomplete rescue from toxicity due to dCF and AdR. In patients with ADA deficiency or treated with ADA inhibitors, both mechanisms could be operative. These observations are also relevant to the possible use of dCF and AdR as immunosuppressive agents and for the removal of T-cells or residual Thy-ALL blasts from bone marr
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PMID:Mechanisms of deoxyadenosine toxicity in human lymphoid cells in vitro: relevance to the therapeutic use of inhibitors of adenosine deaminase. 623 Oct 47

Deficiencies of two enzymes that catalyze sequential reactions in the purine catabolic pathway have been causally associated with immunodeficiency states. Adenosine deaminase (ADA) deficiency results in severe combined immunodeficiency disease, while purine nucleoside phosphorylase (PNP) deficiency results in an isolated T-cell defect. Recent work in this area has provided major new insights into the molecular pathology of these syndromes. Deoxyadenosine and deoxyguanosine, substrates that accumulate in ADA and deoxyguanosine, substrates that accumulate in ADA and PNP deficiency, respectively, appear to be selectively phosphorylated by lymphoid cells to the corresponding deoxynucleoside triphosphate, resulting in inhibition of DNA synthesis in these cells. Both deoxynucleosides are far more toxic to cultured T lymphoblasts than to B lymphoblasts. Adenosine and deoxyadenosine may have additional lymphotoxic effects mediated by inhibition of essential methylation reactions. These observations help to explain the immunologic manifestations of ADA and PNP deficiency. Perhaps more important, they lay the foundation for the use of deoxynucleosides or enzyme inhibitors, or both, as selective immunosuppressive and chemotherapeutic agents.
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PMID:Purinogenic immunodeficiency diseases: clinical features and molecular mechanisms. 624 48

The association of a genetic deficiency of adenosine deaminase (ADA) with immunodeficiency disease has emphasized the importance of deoxyadenosine and adenosine metabolism for human lymphocyte function. However, information concerning the endogenous production and metabolism of deoxyadenosine and adenosine in normally growing human T and B lymphoblasts is lacking. In the present experiments, we used a diverse series of cell lines deficient in individual enzymes of purine metabolism to quantitate the de novo formation of deoxyadenosine and adenosine in human T lymphoblasts (CEM), B lymphoblasts (WI-L2), and histiocytic lymphoma cells (DHL-9). The B lymphoblasts and histiocytic lymphoma cells generated deoxyadenosine at a rate of 60 to 80 pmol/hr/10(7) cells. This value was several fold greater than the rate of production of deoxyadenosine by T cells (6 to 7 pmol/hr/10(7) cells). Deoxyadenosine synthesis required ribonucleotide reductase activity, and was maximal during the S-phase of the cell cycle. The T and B lymphoblasts formed relatively similar amounts of adenosine (870 to 1620 pmol/hr/10(7) cells) throughout the cell cycle. In ADA-deficient cells, a major fraction of the deoxyadenosine synthesized de novo was excreted into the extracellular space. These results establish that the endogenous synthesis and metabolism of deoxyadenosine (but not adenosine) is distinctly different in T and B lymphoblasts.
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PMID:Differential production of deoxyadenosine by human T and B lymphoblasts. 635 3

We investigated adenosine deaminase (ADA) deficient severe-combined immunodeficiency (SCID) in an 8-month-old child with ADA deficient mother. The ADA deficiency in the child was unusual in that the thymic histology was normal. In addition, the thymocytes formed E-rosettes with sheep erythrocytes and were stimulated by T-cell mitogens. ADA activity could not be detected in the child's thymocytes. Studies on the family indicated that the father had about one-half of the normal erythrocyte ADA activity. All the family members with detectable ADA activity appeared to have, according to starch gel electrophoresis of erythrocyte lysates, the common ADA-1 phenotype; however, rigorous identification of phenotype was not possible in this study. The mother had less than 1% of normal ADA activity in both erythrocyte and lymphocyte extracts, but her whole peripheral blood lymphocytes demonstrated about 6% of normal activity. Normal concentrations of ATP and small amounts of dATP were found in the mother's erythrocytes. Deoxyadenosine excretion in her urine was elevated and approximately 5-10% of that excreted by individuals with ADA deficient SCID. These studies suggest that low amounts of ADA activity in erythrocytes and blood lymphocytes of certain individuals may be compatible with good immune function and longevity.
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PMID:Severe combined immunodeficiency in a child with a healthy adenosine deaminase deficient mother. 660 96

We examined the genetic basis for adenosine deaminase (ADA) deficiency in seven patients with late/delayed onset of immunodeficiency, an underdiagnosed and relatively unstudied condition. Deoxyadenosine-mediated metabolic abnormalities were less severe than in the usual, early-onset disorder. Six patients were compound heterozygotes; 7 of 10 mutations found were novel, including one deletion (delta 1019-1020), three missense (Arg156 > His, Arg101 > Leu, Val177 > Met), and three splicing defects (IVS 5, 5'ss T+6 > A; IVS 10, 5'ss G+1 > A; IVS 10, 3'ss G-34 > A). Four of the mutations generated stop signals at codons 131, 321, 334, and 348; transcripts of all but the last, due to delta 1019-1020, were severely reduced. delta 1019-1020 (like delta 955-959, found in one patient and apparently recurrent) is at a short deletional hot spot. Arg156 > His, the product of which had detectable activity, was found in three patients whose second alleles were unlikely to yield active ADA. The oldest patient diagnosed was homozygous for a single base change in intron 10, which activates a cryptic splice acceptor, resulting in a protein with 100 extra amino acids. We speculate that this "macro ADA," as well as the Arg156 > His, Arg101 > Leu, Ser291 > Leu, and delta 1019-1020 products, may contribute to mild phenotype. Tissue-specific variation in splicing efficiency may also ameliorate disease severity in patients with splicing mutations.
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PMID:Novel splicing, missense, and deletion mutations in seven adenosine deaminase-deficient patients with late/delayed onset of combined immunodeficiency disease. Contribution of genotype to phenotype. 822 44


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