Correlations between purine levels, clinical and immunological status in ADA deficiency

Analysis of purine metabolic enzymes in human CD4 Leu 8- and CD4 Leu 8+ lymphocyte subpopulations

1. Specific activities of adenosine deaminase, purine nucleoside phosphorylase, adenosine kinase, 5'-nucleotidase, S-adenosyl-L-homocysteine hydrolase, AMP deaminase, adenine phosphoribosyl transferase, and hypoxanthine phosphoribosyl transferase were analyzed in human CD4 T-lymphocyte subsets. 2. CD4 Leu 8- (helper/inducer) and CD4 Leu 8+ (suppressor/inducer) subpopulations were obtained by panning or fluorescence activated cell sorting techniques using specific monoclonal antibodies. 3. A 45% decrease of 5'-NT AMP activity in the CD4 Leu 8- cells (suppressor/inducer) compared with CD4 total cell population. 4. No statistical significant differences in enzyme activity were found between the subsets analyzed in other purine enzymes. 5. These results suggest that the distribution of purine metabolic enzymes is homogeneous in CD4 Leu 8- and CD4 Leu 8+ T-lymphocyte subpopulations.

Interleukin 2 responsive lymphocytes in patients with adenosine deaminase deficiency

We evaluated the effects of recombinant interleukin 2 (IL-2) on the proliferative responses to mitogens of peripheral blood mononuclear cells (PBMC) from three adenosine deaminase (ADA)-deficient patients. There was significant enhancement by IL-2 of the proliferative responses to phytohemagglutinin (PHA) and pokeweed mitogen (PWM) of PBMC from all three patients. We found that normal PBMC respond with increased numbers of CD3-positive cells when exposed to PHA or PWM and that the response by normal CD8-positive cells was greater than that by CD4-positive cells. In contrast, we found that in ADA-deficient cells the response is almost entirely due to the CD3/CD4-positive population of lymphocytes. These results could not be explained by either the culture conditions or the possibility of a mixed chimeric state. When we evaluated an in vitro cell model of ADA deficiency using an ADA inhibitor, erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA), we found that the inhibitory effect of EHNA plus deoxyadenosine on mitogen-stimulated PBMC could not be prevented by IL-2. These results suggest that the immunodeficiency in ADA deficiency includes the absence or failure of a subset of T cells to make IL-2 and the failure of the CD8-positive subset to respond to IL-2. Also, the in vitro cell model of ADA deficiency using EHNA as the ADA inhibitor is limited in its use in understanding the pathogenesis of this disease.

Prenatal diagnosis of purine nucleoside phosphorylase deficiency in the first and second trimesters of pregnancy

Prenatal diagnosis was performed in two successive pregnancies of a mother with a previous child with purine nucleoside phosphorylase (PNP) deficiency. In one pregnancy, an affected fetus was diagnosed in the 18th week of gestation after the demonstration of PNP deficiency in cultured amniotic fluid cells. Also an abnormal purine nucleoside profile was found in the amniotic fluid. The diagnosis of an affected fetus was confirmed by the analysis of cultured fetal skin fibroblasts and placental villi. The complete deficiency of PNP activity in placental villi confirms that the prenatal diagnosis of this disorder is possible by the direct investigation of chorionic villi. In the subsequent pregnancy, a heterozygous fetus was predicted in the tenth week of pregnancy by using chorionic villi.

First trimester diagnosis of adenosine deaminase deficiency

Adenosine deaminase deficiency has been detected in the first trimester by direct analysis of enzyme activity in chorionic villi in a pregnancy at risk. Data for purine nucleoside phosphorylase activity in chorionic villi from healthy controls in the first trimester are also presented and should allow equally rapid diagnosis of this disorder.

Use of intact erythrocytes in the diagnosis of inherited purine and pyrimidine disorders

This paper reports the detection of five inherited disorders of purine and one of pyrimidine metabolism using intact red blood cells (RBCs) and compares the findings with those from RBC lysate activity. Two different phosphate levels (1 and 18 mmol L-1 Pi) were used to evaluate endogenous PP-ribose-P levels and their generation by PP-ribose-P synthetase. The importance of this dual approach is demonstrated by the following evidence: (a) Six out of eight patients with no detectable hypoxanthine-guanine phosphoribosyltransferase (HGPRT) RBC lysate activity had up to 25% of normal activity in their intact RBCs. Two Lesch-Nyhan patients showed no detectable activity in intact or lysed RBCs. (b) RBC lysates from two heterozygotes for adenosine deaminase (ADA) deficiency also showed no detectable activity, but up to 60% of normal activity using intact RBCs. (c) The existence of an aberrant enzyme in a kindred with a superactive PP-ribose-P synthetase was evident from the fact that intact RBCs failed to respond normally to phosphate activation, despite normal HGPRT and adenine phosphoribosyltransferase (APRT) RBC lysate activity. (d) Raised endogenous PP-ribose-P levels in intact RBCs were demonstrable only in purine nucleoside phosphorylase (PNP) and HGPRT deficiency; levels were normal in APRT deficiency and hereditary oroticaciduria (OPRT/ODC) deficiency. The results indicate that diagnosis from RBC lysate activity alone may be misleading. Intact RBC studies clearly provide a better indication of the functional capacity of the enzyme in vivo. They also show a closer correlation with the clinical phenotype and allow further insight into the associated biochemical abnormalities in some cases.