Combined immunodeficiency disease associated with adenosine deaminase deficiency. Report on a workshop held in Albany, New York, October 1, 1973

Primary and secondary defects of the thymus

The thymus is the primary site of T-cell development, enabling generation, and selection of a diverse repertoire of T cells that recognize non-self, whilst remaining tolerant to self- antigens. Severe congenital disorders of thymic development (athymia) can be fatal if left untreated due to infections, and thymic tissue implantation is the only cure. While newborn screening for severe combined immune deficiency has allowed improved detection at birth of congenital athymia, thymic disorders acquired later in life are still underrecognized and assessing the quality of thymic function in such conditions remains a challenge. The thymus is sensitive to injury elicited from a variety of endogenous and exogenous factors, and its self-renewal capacity decreases with age. Secondary and age-related forms of thymic dysfunction may lead to an increased risk of infections, malignancy, and autoimmunity. Promising results have been obtained in preclinical models and clinical trials upon administration of soluble factors promoting thymic regeneration, but to date no therapy is approved for clinical use. In this review we provide a background on thymus development, function, and age-related involution. We discuss disease mechanisms, diagnostic, and therapeutic approaches for primary and secondary thymic defects.

Inborn errors of immunity associated with defects of thymic development

The main function of the thymus is to support the establishment of a wide repertoire of T lymphocytes capable of eliminating foreign pathogens, yet tolerant to self-antigens. Thymocyte development in the thymus is dependent on the interaction with thymic stromal cells, a complex mixture of cells comprising thymic epithelial cells (TEC), mesenchymal and endothelial cells. The exchange of signals between stromal cells and thymocytes is referred to as "thymic cross-talk". Genetic defects affecting either side of this interaction result in defects in thymic development that ultimately lead to a decreased output of T lymphocytes to the periphery. In the present review, we aim at providing a summary of inborn errors of immunity (IEI) characterized by T-cell lymphopenia due to defects of the thymic stroma, or to hematopoietic-intrinsic defects of T-cell development, with a special focus on recently discovered disorders. Additionally, we review the novel diagnostic tools developed to discover and study new genetic causes of IEI due to defects in thymic development. Finally, we discuss therapeutic approaches to correct thymic defects that are currently available, in addition to potential novel therapies that could be applied in the future.

Protein Arginine Methyltransferase 5 in T Lymphocyte Biology

Protein arginine methyltransferase 5 (PRMT5) is the major methyltransferase (MT) catalyzing symmetric dimethylation (SDM). PRMT5 regulates developmental, homeostatic and disease processes in vertebrates and invertebrates, and a carcinogenic role has been observed in mammals. Recently, tools generated for PRMT5 loss of function have allowed researchers to demonstrate essential roles for PRMT5 in mouse and human lymphocyte biology. PRMT5 modulates CD4⁺ and CD8⁺ T cell development in the thymus, peripheral homeostasis, and differentiation into CD4⁺ helper T lymphocyte (Th)17 cell phenotypes. Here, we provide a timely review of the milestones leading to our current understanding of PRMT5 in T cell biology, discuss current tools to modify PRMT5 expression/activity, and highlight mechanistic pathways.

Adenosine deaminase activity in type 2 diabetes mellitus: does it have any role?

BACKGROUND

Diabetes mellitus is a group of metabolic disorders of carbohydrate metabolism in which glucose is underused, producing hyperglycemia. Diabetic patients are prone to opportunistic infection, thus serum ADA levels in these patients is very important as a screening test for Tuberculosis and autoimmune diseases. Thus, the present study was conducted to estimate the Serum ADA activity, glycated Haemoglobin (HbA1c), fasting and postprandial glucose level in patients with T2DM and to correlate the serum level of ADA with glycated Hemoglobin (HbA1c), fasting and postprandial glucose level in T2DM.

METHODS

This is a Hospital based cross-sectional study done in BPKIHs, Dharan, Nepal. 204 diagnosed patients (102 males and 102 females) with T2DM and 102 healthy controls were enrolled in the study. Diabetic patients were categorized into Uncontrolled and Controlled Diabetes on the basis of HbA1C; HbA1c > 7% = Uncontrolled Diabetes, HbA1c < 7% = Controlled Diabetes.

RESULTS

Serum ADA levels (U/L) was significantly raised in Uncontrolled Diabetic patients (49.24 ± 16.89) compared to controlled population (35.74 ± 16.78) and healthy controls (10.55 ± 2.20), p value < 0.001. A significant positive correlation was obtained between Serum ADA and HbA1c, Fasting Plasma Glucose and Post-prandial Glucose respectively.

CONCLUSION

There is a significant increase in Serum ADA activity in DM with increase in HbA1c levels which may play an important role in predicting the glycemic and immunological status in these patients.

The Organogermanium Compound Ge-132 Interacts with Nucleic Acid Components and Inhibits the Catalysis of Adenosine Substrate by Adenosine Deaminase

Poly-trans-[(2-carboxyethyl)germasesquioxane] (Ge-132) is a water-soluble organogermanium compound that exerts various physiological effects, including anti-inflammatory activity and pain relief. In water, Ge-132 is hydrolyzed to 3-(trihydroxygermyl)propanoic acid (THGP), which in turn is capable of interacting with cis-diol compounds through its trihydroxy group, indicating that this compound could also interact with diol-containing nucleic acid constituents. In this study, we evaluated the ability of THGP to interact with nucleosides or nucleotides via nuclear magnetic resonance (NMR) analysis. In addition, we evaluated the effect of added THGP on the enzymatic activity of adenosine deaminase (ADA) when using adenosine or 2'-deoxyadenosine as a substrate. In solution, THGP indeed formed complexes with nucleotides or nucleosides through their cis-diol group. Moreover, the ability of THGP to form complexes with nucleotides was influenced by the number of phosphate groups present on the ribose moiety. Notably, THGP also inhibited the catalysis of adenosine by ADA in a concentration-dependent manner. Thus, interactions between THGP and important biological nucleic acid constituents might be implicated in the physiological effects of Ge-132.

Adenosine production: a common path for mesenchymal stem-cell and regulatory T-cell-mediated immunosuppression

Adenosine is an important molecule that exerts control on the immune system, by signaling through receptors lying on the surface of immune cells. This nucleotide is produced, in part, by the action of the ectoenzymes CD39 and CD73. Interestingly, these proteins are expressed on the cell surface of regulatory T-cells (Tregs) and mesenchymal stromal cells (MSCs)-two cell populations that have emerged as potential therapeutic tools in the field of cell therapy. In fact, the production of adenosine constitutes a mechanism used by both cell types to control the immune response. Recently, great scientific progress was obtained regarding the role of adenosine in the inflammatory environment. In this context, the present review focuses on the advances related to the impact of adenosine production over the immune modulatory activity of Tregs and MSCs, and how this nucleotide controls the biological functions of these cells. Finally, we mention the main challenges and hurdles to bring such molecule to clinical settings.

Long-term neurocognitive function of pediatric patients with severe combined immune deficiency (SCID): pre- and post-hematopoietic stem cell transplant (HSCT)

Background

Hematopoietic stem cell transplantation (HSCT) is the only cure for patients with severe combined immunodeficiency (SCID). The purpose of this study was to evaluate long-term neurodevelopment of patients with SCID following myeloablative chemotherapy and HSCT.

Materials and Methods

Sixteen pediatric patients diagnosed with SCID were tested using the Bayley Scales of Infant Development and the validated Vineland Adaptive Behavior Scales (VABS) pre- and 1-year post-HSCT. Three years post-HSCT, there were 11 patients available for testing and four patients available 5 years post-HSCT. Patients greater than 3 years of age were administered the Wechsler Preschool and Primary Scale of Intelligence. Both raw scores and scaled scores were analyzed.

Results

There was a significant decrease 1 year post-HSCT in the Bayley Mental Developmental Index (MDI) [92.5 (pre) vs. 70.81 (1 year post), p < 0.0001] and the VABS [99.73 (pre) vs. 79.87 (1 year post), p = <0.0001]. There was a significant decrease over time in the MDI [95.00 (pre) vs. 72.64 (1 year post) vs. 71.82 (3 years post), p < 0.0001], but no significant change between 1 and 3 years post-HSCT. There was no change in the Bayley Psychomotor Development Scale (PDI) [82.4 (pre) vs. 84.8 (1 year post), p = 0.68]. The PDI scores decreased over time [86.29 (pre) vs. 86 (1 year post) vs. 74.14 (3 years post), p = 0.045]. Although there was a decrease in scaled scores, there was not a loss of skills. Analysis of raw scores showed that there was an increase in the raw test scores, which indicated that these children acquired developmental skills, but at a slower rate than normal infants and toddlers. Younger children had a more significant decrease in adaptive scores compared with older children.

Conclusions

These findings may reflect the effects of the isolation and prolonged hospitalization that characterizes the immediate post-transplant period. Patients miss out on social interactions and learning opportunities that normally occur at their respective stages of development. These restrictions keep patients from acquiring developmentally appropriate cognitive skills as well as gross and fine motor developmental milestones. Longitudinal follow-up will be important to quantify acquisition of skills.

The effect of adenosine on lymphoid cell proliferation and antibody formation

The discovery of an association of certain primary defects in human purine metabolism with immunodeficiency disease has served to focus attention on the possible role of purine compounds in the functional activity of lymphoic cells. Considerable evidence has accumulated of the need within the intact organism for purine and pyrimidine compounds supplied by the liver as a supplementary nutritional requirement for the growth of the rapidly proliferating tissues of certain organ systems. Likewise, lymphoid cells cultured in vitro show evidence of an enhancement of indices of cellular proliferation and of antibody synthesis when exogenous adenosine is added to the medium. These functions are inhibited by high concentrations of adenosine and there is some evidence that T-cell proliferation shows a greater sensitivity to inhibition by adenosine than B-cells. These observations may be significant in relation to the known defects in human purine metabolism and their mechanism for producing immunodeficiency.

Anti-adenosine deaminase antibodies in lupus erythematosus

Adenosine deaminase (ADA) is an enzyme involved in purine metabolism and has a major role in the development and function of lymphoid cells. Congenital deficiency of ADA results in severe immunodeficiency. Patients with congenital ADA deficiency treated with polyethylene glycol-conjugated bovine ADA develop antibodies to ADA. This leads us to investigate the role of anti-ADA antibodies in patients with systemic rheumatic diseases. Commercially available ADA was used in ELISA and immunoblots for detection of anti-ADA antibodies. Four out of 100 patients examined were positive for anti-ADA antibodies. Two of them had peripheral blood lymphopenia but the antibody levels did not appear to correlate with the lymphocyte counts. Immunoblotting revealed that the antibodies recognized a 40 kDa peptide of ADA, corresponding to ADA1, the major component of ADA. Affinity-purified antibodies were used to locate the distribution of ADA on Hep-2 cells and lymphocytes by indirect immunofluorescence. Anti-ADA antibodies gave a distinct nuclear speckled pattern on acetone-fixed cells. With viable cell immunofluorescence, anti-ADA antibodies also stained the cell surface of HEp-2 cells and lymphocytes, indicating surface expression of ADA. The anti-ADA antibodies failed to gain access into the cytoplasm or nuclei when added to the cultures of HEp-2 cells. In summary, this is the first report of detection of anti-ADA1 autoantibody which is a new type of ANA with discrete, speckled nuclear staining, but which may not be associated with lymphopenia.

Bone marrow transplantation for nonmalignant diseases

Bone marrow transplantation (BMT) has emerged as a major therapeutic option for a number of nonmalignant disorders affecting the bone marrow and leading to clinical manifestations most likely affecting distant organs. Disorders such as autoimmune diseases, metabolic disorders, hemoglobinopathies, immunodeficiencies, and others have been the target of high-dose therapy and autologous or allogeneic bone marrow, stem cell, or cord blood transplantation. Successful results have been reported in a large number of these disorders. In most instances the goal of transplantation is to provide sufficient degree of marrow engraftment to allow long-term amelioration of disease phenotype. For many of these disorders, early diagnosis is crucial in achieving the desired results as transplantation becomes difficult when significant end-organ damage sets in. Major unsolved problems, including toxicity of conditioning regimens, graft-versus-host disease, and donor availability, need to be addressed. We attempt to provide a comprehensive review of BMT and discuss unique features of this modality for treatment of nonmalignant disorders.

Gene therapy for adenosine deaminase deficiency

The clinical gene therapy trials for adenosine deaminase (ADA) deficiency have defined both the potential benefits and the present limitations of gene therapy with hematopoietic stem cells (HSC). Current clinical results indicate that (a) both umbilical cord blood and neonatal bone marrow HSC can be transduced with murine retroviral-based vectors, (b) the transduced HSC can engraft in nonmyeloablated patients, (c) the frequency of HSC transduction/engraftment is low (1/10,000), (d) an in vivo selective advantage can exist for transduced T lymphoid progeny, and (e) the transduced ADA gene is not expressed in nondividing T lymphocytes. Improving the clinical results of gene therapy for ADA deficiency and other genetic diseases involving HSC will require (a) developing new vectors that express the transduced gene in nondividing cells and (b) increasing the frequency of stable HSC transduction.

Spondylo-mesomelic-acrodysplasia with joint dislocations and severe combined immunodeficiency: a newly recognised immuno-osseous dysplasia

A newborn girl is described with an association of spondylo-acrodysplasia, mild short limbed dwarfism without significant metaphyseal changes, joint dislocations, and severe immune system dysfunction. This association is distinct from other known immuno-osseous dysplasias, including Schimke dysplasia, ADA deficiency with osseous changes, and Omenn phenotype with short limbed dwarfism.

On the phosphorylation of 2-chlorodeoxyadenosine (CdA) and its correlation with clinical response in leukemia treatment

The nucleoside analog 2-chlorodeoxyadenosine (CdA, Cladribine) is a chemotherapeutic agent for treatment of leukemias and lymphomas, most successfully used in hairy cell leukemia and B-cell chronic lymphocytic leukemia. CdA is phosphorylated intracellularly to its monophosphate derivative by the enzymes deoxycytidine kinase and deoxyguanosine kinase. Cell lines deficient in deoxycytidine kinase were shown to be resistant to CdA and a high deoxycytidine kinase level in combination with low 5'-nucleotidase has been proposed to partly explain the selectivity in CdA toxicity for lymphoid cells. In this report biochemical properties in CdA phosphorylation mediated by deoxycytidine kinase and deoxyguanosine kinase are reviewed and discussed in relation to the further metabolism of CdA 5'-monophosphate, the different possible mechanisms of action and the correlation with clinical response. It is concluded that much is known about the metabolism and mechanisms of action of CdA, but that the remarkable therapeutic effect in hairy cell leukemia has yet to be explicitly explained.

Purine nucleoside therapy of low-grade follicular lymphoma

Low-grade follicular lymphomas, follicular small cleaved and follicular mixed, generally follow an indolent but progressive course. Although available therapies induce responses, continuous relapse occurs. In investigating potential therapeutic regimens, researchers have sought regimens that will result in a postchemotherapy survival plateau rather than a pattern of continuous relapse. The newer, purine analogs, 2'-deoxycoformycin, fludarabine, and 2-chlorodeoxyadenosine have shown activity in the low-grade B-cell lymphomas, especially with the follicular histologic subtype. Response rates in studies of previously untreated patients approach 100%. The newer purine analogs are emerging as an important treatment approach for indolent B-cell lymphomas, but the impact on survival remains to be assessed.

Adenosine-induced apoptosis in chick embryonic sympathetic neurons: a new physiological role for adenosine

1. A newly found action of adenosine in neurons, which may have an important physiological function in the growth and development of the sympathetic nervous system, is described. Adenosine (1-100 microM) inhibited neurite outgrowth within the first 24 h and killed about 80% of sympathetic neurons supported by nerve growth factor over the next 2 days in culture. Neurons supported by excess KCl, forskolin or phorbol 12,13-dibutyrate were equally susceptible to the toxic actions of adenosine. Inosine, guanosine or hypoxanthine (all 100-300 microM) were without effect on neuronal growth and survival. 2. Specific agonists of adenosine A1 and A2 receptors were not neurotoxic, and toxic effects of adenosine were not antagonized by aminophylline. These results rule out involvement of adenosine receptors and the adenylyl cyclase-cAMP signalling system in neurotoxic actions of adenosine. 3. Adenosine toxicity was prevented by inhibitors of the adenosine membrane transporter, suggesting an intracellular site of action of adenosine. 4. Inhibitors of adenosine deaminase dramatically facilitated the toxic action so that physiologically relevant concentrations of adenosine were neurotoxic. 5. Adenosine kinase activity of sympathetic neurons was dose-dependently inhibited by 5'-iodotubercidin (3-100 nM). 5'-Iodotubercidin (100 nM) completely protected neurons against toxicity of adenosine plus adenosine deaminase inhibitors. These results provide convincing evidence that phosphorylation of the nucleoside is an essential requirement for initiation of adenosine toxicity. 6. Sympathetic neurons were successfully rescued from the lethal effects of adenosine deaminase inhibitor plus adenosine by uridine or 2-deoxycytidine, but not by nicotinamide or 2-deoxyguanosine, suggesting that depletion of pyrimidine nucleotides by phosphorylated adenosine compounds and consequent inhibition of DNA synthesis produces neuronal death. 7. DNA fragmentation, assessed by the fluorescent dye bisbenzimide and by the TUNEL (terminal deoxynucleotidyl transferase-mediated nick end labelling) method, indicated that neuronal death induced by adenosine was apoptotic. 8. We conclude that adenosine deaminase and adenosine kinase play an important role in the metabolism of intracellular concentrations of adenosine and thereby regulate the growth and development of sympathetic neurons. Our study highlights, for the first time, the importance of adenosine as a mediator of programmed cell death of neurons supported by nerve growth factor.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD)-induced reduction of adenosine deaminase activity in vivo and in vitro

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a potent immunosuppressant in several animal species. The purpose of this study was to determine if TCDD affected the activity of adenosine deaminase (ADA), a purine metabolizing enzyme that is vital to the proper functioning of the immune system. The effect of TCDD on ADA activity was studied in various tissues of male Balb/c mice (a TCDD-responsive strain) and DBA/2 mice (a less-responsive strain). Of the tissues examined after administration of TCDD in vivo (115 micrograms/kg, i.p.), ADA activity was found to be significantly reduced in thymic and splenic tissues of Balb/c mice at 24 hours postadministration. The enzyme activity in these affected tissues remained consistently low through 10 days postadministration. Such an effect of TCDD was both dose and time related in the thymic tissue of Balb/c mice. In contrast, no appreciable alterations in ADA activity were evident in any of the tissues of DBA/2 mice at any of the sampling intervals, indicating that such an effect of TCDD is likely to be mediated through the Ah receptor. This in vivo effect of TCDD on thymic ADA activity was also reproducible in situ where isolated whole thymuses were directly incubated with 10 nM TCDD. In this model, TCDD's effects on ADA activity were antagonized by known protein kinase or phosphorylation inhibitors such as quercetin, genistein, tyrphostin, and neomycin. These results indicate that the effect of TCDD on ADA activity in the thymus may be related to its property to elevate protein kinase activities in this tissue. ADA activity was also reduced in 3T3 cells that were treated with 10 nM TCDD in a low (1%) serum media. In contrast, 25 ng/mL epidermal growth factor (EGF) under such conditions consistently stimulated ADA activity. Interestingly, EGF at a similar concentration failed to elicit a stimulatory effect on ADA activity when cells were pretreated with TCDD. The property of TCDD to lower ADA activity under in vivo, in situ, as well as in vitro conditions appears to be largely related to its action to modulate protein phosphorylation activities.

Juvenile variant of Schimke immunoosseous dysplasia

We report on a 16-year-old girl with spondyloepiphyseal dysplasia, nephrotic syndrome, lymphopenia, and signs of defective cellular immunity. The manifestations are very similar to those reported by Spranger et al. [1991: J. Pediatr 119: 64-72] as Schimke immunoosseous dysplasia, except for age of onset. In Schimke immunoosseous dysplasia, growth retardations as an initial symptom is noted in early childhood and about 1 year after onset of progressive proteinuria. In our case the skeletal abnormality was noted at age 10 years as dislocation of the hip joints and the diagnosis of nephrotic syndrome was made at age 16 years. The findings strongly suggest that our patient has a juvenile variant of Schimke immunoosseous dysplasia.

Activation of apoptosis in early mouse embryos by 2'-deoxyadenosine exposure

Adenosine deaminase (ADA) catalyzes the irreversible hydrolytic deamination of adenosine and deoxyadenosine to nontoxic derivatives. The importance of this reaction in the female reproductive tract of mice is suggested by pronounced utero-placental expression of ADA, and by embryolethality of the potent ADA-inhibitor deoxycoformycin (dCF) on day 7-8 of gestation. The present study investigated the effects of dCF, adenosine, and deoxyadenosine on the mouse neurula. Morphological cell death was monitored by the acridine orange reaction (AOR), and biochemical cell death by internucleosomal DNA cleavage (IDC). A strong AOR appeared in day 7-8 embryos between 3 and 4.5 hr post-exposure to dCF in utero; there was no apparent effect on day 6 or day 9 embryos. Most embryonic tissues were responsive, although the heart and extraembryonic membranes were resistant. Up to 75% of the embryonic chromatin was degraded in a regular pattern in concert with the AOR. Immediate activation of "whole-body" apoptosis was reproduced in short-term whole embryo culture with 0.1 mM deoxyadenosine in the presence of 0.01 mM dCF. This was not activated by exposure to dCF alone nor to adenosine; however, high concentrations of adenosine completely blocked the response to deoxyadenosine, whereas niacinamide inhibited the AOR without changing IDC. The cytotoxic effect of deoxyadenosine was correlated with an expansion of embryonic dATP pools determined by high-performance liquid chromatography analysis. The results suggest that deoxyadenosine is the embryotoxic metabolite which accumulates in the antimesometrium of pregnant mice treated with dCF. Exposure to this metabolic toxin activates apoptosis in day 7-8 embryos through an adenosine-sensitive, NAD-dependent mechanism.

Pentostatin: an adenosine deaminase inhibitor for the treatment of hairy cell leukemia

OBJECTIVE

To review the pharmacology, pharmacokinetics, adverse effects, and various dosage regimens of pentostatin, and to evaluate the role of pentostatin in the treatment of hairy cell leukemia (HCL).

DATA IDENTIFICATION

Articles were identified via an English-language literature search of MEDLINE (1966-91) and an extensive search of bibliographies from identified articles.

STUDY SELECTION

Human clinical trials and case reports were selected for evaluation.

DATA EXTRACTION

The literature was assessed for quality, methodology, and outcome information.

DATA SYNTHESIS

At dosages of 4 mg/m2 administered every other week for 6-9 months, pentostatin has been shown to successfully induce a complete response in 58-90 percent of patients and to produce a partial response in up to 30 percent of patients with HCL. The median time to achieve a response is 4.7 months. Long-term remissions of at least 14 months' duration have occurred in some patients. Compared with interferon alfa alone, total response rates are not significantly different when pentostatin and interferon alfa are used in combination. When dosed appropriately, pentostatin is generally well tolerated. Common adverse effects include nausea, vomiting, myelosuppression, fever, and infection.

CONCLUSIONS

Pentostatin is a purine analog that inhibits adenosine deaminase, a key enzyme necessary for purine salvage. Pentostatin has received labeling approval for the treatment of HCL refractory to a minimum of three to six months of treatment with interferon alfa. Based on current data, pentostatin will be a useful addition to the therapeutic agents presently available to patients with HCL. Ongoing trials are evaluating the effectiveness of pentostatin as first-line therapy for patients with HCL.

Adenosine-deaminase-associated immunodeficiency. I. Differential sensitivities of lymphocyte subpopulations exposed to 2-deoxycoformycin in vivo

In order to obtain a better understanding of the degree of immune dysfunctions caused by the absence of adenosine deaminase, we gave a single i.p. injection of 2'-deoxycoformycin (2-dcf), a potent inhibitor of the enzyme ADA at various doses into adult Syrian hamsters. These animals were examined for their ability to mount primary in vivo antibody responses to helper T cell dependent (Th-d) and helper T cell independent (Th-ind) antigens. Hamsters treated with 0.5 mg/kg of 2-dcf mounted enhanced splenic plaque-forming cell (PFC) responses to sheep erythrocytes, a Th-d antigen, and to pneumococcal polysaccharide type III (SIII), a Th-ind antigen. Treatment of animals with 1.0 mg/kg of 2-dcf resulted in a significantly depressed (P less than 0.001) PFC response to Th-d antigen, but a further enhanced response to Th-ind antigen. One mechanism which may be responsible for such a dichotomous response to these two types of antigens was selective dysfunction of T cell subpopulations. At higher doses (1.5-4.0 mg/kg), PFC responses to both types of antigens were significantly suppressed. Immunoenhancement at low doses of 2-def was attributed to an increased susceptibility of T suppressor cells to 2-dcf. This hypothesis was confirmed by priming the 2-dcf-treated animals with low-dose Th-ind antigens. These animals failed to induce low-dose tolerance by stimulation of antigen-specific suppressor T cell subsets. At low doses, B cells and T helper cell functions were found to be intact, as further confirmed by priming the animals with the carrier keyhole limpet haemocyanin (KLH) and challenging with trinitrophenyl-KLH. This dose-dependent selective susceptibility of various T cell subpopulations and B cells may explain the heterogeneity of clinical, biochemical and immunological parameters observed in children with ADA deficiency severe combined immunodeficiency.

Adenosine deaminase activity in relation to the appearance of early and late Epstein-Barr virus antigens induced in lymphoblastoid cells

Induction of Epstein-Barr virus (EBV) capsid antigen synthesis in 59.6% of P3HR-1 cells was followed by a decrease to 70% in adenosine deaminase (ADA) activity. In Daudi cells synthesizing EBV early antigen, ADA activity did not decrease.

Pegademase bovine: replacement therapy for severe combined immunodeficiency disease

Severe combined immunodeficiency (SCID) represents a syndrome characterized by abnormal function of cellular and humoral immunity. Of the various types of SCID, approximately one-fourth are associated with adenosine deaminase (ADA) deficiency. Treatment consists of bone marrow transplantation, red blood cell transfusions, enzyme replacement, and, more recently, gene therapy. Pegademase bovine is the sole agent available for enzyme replacement therapy of SCID associated with ADA deficiency. The drug is administered intramuscularly to infants from birth and to children of any age at time of diagnosis. At present, few adverse effects or drug interactions have been documented. Although it is expensive (approximately $60,000 annually), pegademase bovine offers an alternative to standard means of therapy.

Schimke immuno-osseous dysplasia: a newly recognized multisystem disease

On the basis of five cases personally observed and one previously reported, we describe a disorder characterized by skeletal dysplasia, rapidly progressive nephropathy, episodes of lymphopenia, and pigmentary skin changes. Defects of T-cell function were compatible with an autoimmune process. The disorder is probably of genetic origin and inherited as an autosomal recessive trait.

Short stature/short limb skeletal dysplasia with severe combined immunodeficiency and bowing of the femora: report of two patients and review

We report two patients with severe combined immunodeficiency and short stature/short limb skeletal dysplasia. Case 1 presented at birth with rhizomelic shortening of the extremities and bowing of the femora. She developed clinical signs of severe combined immunodeficiency at 13 months and died at 21 months. Case 2 had severe prenatal shortening and bowing of the extremities and a small, malformed chest. Symptoms of severe combined immunodeficiency and severe failure to thrive developed soon after birth and she died at 5 months. The diagnosis of severe combined immunodeficiency in our patients was based on their clinical course and necropsy findings, supported in case 1 by the results of immune function tests. The results of investigation of immune function (immunoglobulins, lymphocyte subpopulations, lymphocyte function) are very variable in this syndrome as in other variants of severe combined immunodeficiency. Bone histopathology in both patients showed grossly irregular costochondral junctions, but normal transition of proliferating to hypertrophic chondrocytes. These cases belong to early lethal type 1 short limb skeletal dysplasia with severe combined immunodeficiency. Review of previously published cases with severe combined immunodeficiency and well documented skeletal findings show eight patients with prenatal onset of bowing and shortening of the extremities and metaphyseal abnormalities. These include two sib pairs concordant for the skeletal changes. In these cases, adenosine deaminase levels were not reported. An additional four published cases with associated adenosine deaminase deficiency had only mild metaphyseal abnormalities, but subsequently showed no linear growth.(ABSTRACT TRUNCATED AT 250 WORDS)

Preparative purification of adenosine deaminase from human erythrocytes by affinity chromatography

The purification of adenosine deaminase from human erythrocytes is reported. By means of classical procedures and by using affinity chromatography as the last step, the enzyme is purified 760,000-fold with a yield of 32%. The affinity resin is composed of purine riboside (nebularine) linked to Sepharose CL6B. Since the compound has no leaving group at the C-6 position the affinity gel is stable and the chromatography can be repeated several times (up to fifteen times in eight months). Purine riboside was chosen because its potency as a reversible inhibitor of adenosine deaminase is greater than that of inosine (a low-affinity inhibitor), but lower than that of erythro-9-(2-hydroxy-3-nonyl)adenine (a high-affinity inhibitor).

Red blood cell enzymes in the diagnosis of genetic disease

Erythrocytes are uniform cells which contain only those proteins that are synthesized during the reticulocyte stage. The relationship of red cell enzymes to gene dosage and gene expression enables the use of red cell enzyme assays to determine the presence or absence of gene defects causing enzyme deficiencies leading to various metabolic diseases; in addition, the mode of inheritance of these defects can frequently be ascertained by analyzing red cell enzymes. However, indirect evidence favoring other enzyme deficiency states can sometimes be obtained from a study of red cell enzyme activities, because apparent enzyme deficiencies may result from the accumulation of inhibitory metabolites formed due to an enzyme deficiency in other tissues. The polymorphic expression of many red cell enzymes lends itself to biochemical analysis which can produce highly accurate and specific diagnostic information.

Differential deoxyadenosine toxicity to immature rabbit cartilage in vitro. A model for the chondro-osseous dysplasia of adenosine deaminase deficiency

Deoxyadenosine metabolism was investigated in rabbit growth plate and articular cartilage to elucidate the biochemical basis for the chondro-osseous dysplasia observed in adenosine deaminase (ADA) deficiency. Models of ADA deficiency, the combination of deoxy-adenosine and either of 2 ADA inhibitors, were selectively toxic to immature cartilage, supporting the hypothesis that the chondro-osseous dysplasia of ADA deficiency is the consequence of the enzyme deficiency. Depletion of ATP may play a role in the altered chondrocyte viability and function observed in this model.

Molecular cloning of the cDNA for a mutant mouse ribonucleotide reductase M1 that produces a dominant mutator phenotype in mammalian cells

Mammalian ribonucleotide reductase is regulated by the binding of dATP and other nucleotide effectors to allosteric sites on subunit M1. Using mRNA from a mutant mouse T-lymphoma (S49) cell line, we have isolated a cDNA which encodes an altered, dATP feedback-resistant subunit M1. The mutant cDNA contains a single point mutation (a G-to-A transition) at codon 57, converting aspartic acid to asparagine. Proof that this mutation is responsible for the phenotype of dATP feedback resistance is provided by the following evidence. (i) The mutation was detected only in mutant S49 cells containing dATP feedback-resistant ribonucleotide reductase and not in wild-type or other mutant S49 cells. (ii) Transfection of Chinese hamster ovary cells with an expression plasmid containing the mutant M1 cDNA resulted in the production of dATP feedback-resistant ribonucleotide reductase. Transfected CHO cells expressing the mutant M1 cDNA exhibited a 15- to 25-fold increase in the frequency of spontaneous mutation to 6-thioguanine resistance, confirming that dATP feedback-resistant ribonucleotide reductase produces a mutator phenotype in mammalian cells. The availability of a cDNA which encodes dATP feedback-resistant subunit M1 thus provides a means of manipulating by transfection the frequency of spontaneous mutation in mammalian cells.

Combined familial adenosine deaminase and purine nucleoside phosphorylase deficiencies

We studied an Arab family in which two infants died of severe combined immunodeficiency caused by adenosine deaminase (ADA) deficiency. One infant had purine nucleoside phosphorylase (PNP) activity in the leucocytes only half that of normal. Four other infant siblings had previously died from infections before the age of 2 months. Hyperpigmented skin lesions preceded death in three cases. The healthy parents and three healthy siblings aged 4-9 years had varying degrees of both ADA and PNP deficiencies in both white and red cells. ADA deficiency was pronounced in two siblings, and mild in the third and in the parents, and PNP activity was severely deficient in one sibling, and moderately deficient in the parents and other two siblings, who were all well. Complete absence of ADA from white cells lead to the development of severe combined immunodeficiency, but even minimal residual ADA and PNP activity allowed maturation of the immune system with normal immune function.

Molecular cloning of the cDNA for a mutant mouse ribonucleotide reductase M1 that produces a dominant mutator phenotype in mammalian cells

Mammalian ribonucleotide reductase is regulated by the binding of dATP and other nucleotide effectors to allosteric sites on subunit M1. Using mRNA from a mutant mouse T-lymphoma (S49) cell line, we have isolated a cDNA which encodes an altered, dATP feedback-resistant subunit M1. The mutant cDNA contains a single point mutation (a G-to-A transition) at codon 57, converting aspartic acid to asparagine. Proof that this mutation is responsible for the phenotype of dATP feedback resistance is provided by the following evidence. (i) The mutation was detected only in mutant S49 cells containing dATP feedback-resistant ribonucleotide reductase and not in wild-type or other mutant S49 cells. (ii) Transfection of Chinese hamster ovary cells with an expression plasmid containing the mutant M1 cDNA resulted in the production of dATP feedback-resistant ribonucleotide reductase. Transfected CHO cells expressing the mutant M1 cDNA exhibited a 15- to 25-fold increase in the frequency of spontaneous mutation to 6-thioguanine resistance, confirming that dATP feedback-resistant ribonucleotide reductase produces a mutator phenotype in mammalian cells. The availability of a cDNA which encodes dATP feedback-resistant subunit M1 thus provides a means of manipulating by transfection the frequency of spontaneous mutation in mammalian cells.

Complete release of adenosine deaminase from mouse lymphocytes stabilized by low-pH acetate

Complete release of adenosine deaminase from mouse lymphocytes takes place when intact cells are stabilized by low-pH acetate buffer. Both the low pH and the acetate affect the enzyme extraction markedly. At pH 5.0 all the adenosine deaminase activity detectable in the whole cell homogenates is released into the acetate buffer in very few minutes, with a total amount of 2% protein being extracted. The complete extraction of the enzyme activity is never observed when, at pH 5.0, the acetate is replaced by glutamate, citrate, succinate or maleate and only 45% and 15% of the adenosine deaminase activity is extracted by the acetate at pH 6.0 and 7.0, respectively. The breakdown of adenosine by the enzyme activity extracted from the stabilized cells is due to deamination alone, since inosine is the only product of the catalyzed reaction and its formation is completely inhibited by coformycin, a selective inhibitor of adenosine deaminase. The enzyme extracted shows a specific activity 50-times higher than that found in the crude homogenates, and a substantial purification of the enzyme extracted is achieved by a single Sephadex G-100 gel filtration.

Inhibition of lymphoid cell growth by adenine ribonucleotide accumulation. The role of phosphoribosylpyrophosphate-depletion induced pyrimidine starvation

The exact role of adenosine in the adenosine deaminase (EC 3.5.4.4) deficiency-related severe combined immunodeficiency disease has not been ascertained. We analysed the effects of adenosine, in the presence of the adenosine deaminase inhibitor, deoxycoformycin, on cell growth, cell phase distributions and intracellular nucleotide concentrations of cultured human lymphoblasts. Adenosine had a biphasic effect on cell growth and cell cycle distribution of a partial hypoxanthine phosphoribosyltransferase (EC 2.4.2.8) deficient MOLT-HPRT cell line. After 24 h of incubation, 60 microM adenosine inhibited cell growth more extensively than did 100 and 200 microM adenosine. The distribution of the MOLT-HPRT cells in the various phases of the cell cycle showed a similar biphasic pattern. Adenosine concentrations in the medium below 10 microM caused accumulation of adenine ribonucleotides and depletion of phosphoribosylpyrophosphate, UTP and CTP in the cells. This was associated with inhibition of cell growth. Medium adenosine concentrations above 10 microM neither resulted in accumulation of adenine ribonucleotides nor in inhibition of cell growth.

Developmental genetics

Of particular concern to the human geneticist are the effects of genetic abnormalities on development. To gain an understanding of these effects it is necessary to engage in a reciprocal process of using knowledge of normal developmental events to elucidate the mechanisms operative in abnormal situations and then of using what is learned about these abnormal situations to expand our understanding of the normal. True developmental genes have not been described in man, although it is likely that they exist, but many developmental abnormalities are ascribable to mutations in genes coding for enzymes and structural proteins. Some of these even produce multiple malformation syndromes with dysmorphic features. These situations provide a precedent for asserting that not only monogenic developmental abnormalities, but also abnormalities resulting from chromosome imbalance must ultimately be explicable in molecular terms. However, the major problem confronted by the investigator interested in the pathogenesis of any of the chromosome anomaly syndromes is to understand how the presence of an extra set of normal genes or the loss of one of two sets of genes has an adverse effect on development. Several molecular mechanisms for which limited precedents exist may be considered on theoretical grounds. Because of the difficulties in studying developmental disorders in man, a variety of experimental systems have been employed. Particularly useful has been the mouse, which provides models for both monogenic and aneuploidy produced abnormalities of development. An example of the former is the mutation oligosyndactylism which in the heterozygous state causes oligosyndactyly and in the homozygous state causes early embryonic mitotic arrest. All whole arm trisomies and monosomies of the mouse can be produced experimentally, and of special interest is mouse trisomy 16 which has been developed as an animal model of human trisomy 21 (Down syndrome). In the long run, the most direct approach to elucidating the genetic problems of human development will involve not only the study of man himself but also of the appropriate experimental models in other species.

Adenosine deaminase deficiency and chondro-osseous dysplasia

An in vitro model of ADA deficiency is selectively toxic to cartilage from immature rabbits with a greater effect on growth plate than articular cartilage. The selective toxicity observed appears to be the consequence of ATP depletion. These results support the hypothesis that the chondro-osseous dysplasia observed in patients with ADA deficiency is caused by the disordered metabolism that results from the enzyme deficiency.