Activities of purine metabolising enzymes in lymphocytes of neonates and young children: correlates with immune function

Abstract

Depressed activities of the following purine enzymes have been shown to result in immunodeficiencies: adenosine deaminase (ADA), hypoxanthine-guanine phosphoribosyltransferase (HGPRT), and purine nucleoside phosphorylase (PNP). These enzymes and adenosine kinase (AK) were measured in cord blood lymphocytes of premature and small-for-gestational age infants since they have partial immunodeficiencies of unknown biochemical etiology which can persist for many years. We also measured these enzymes in 3 infants with various immunodeficiencies. Activities were compared with appropriate matched control groups. The results indicated normal ADA and PNP but significantly depressed AK ( P < 0.05) and HGPRT ( P < 0.001) activities in 10 premature/SGA infants when compared to 35 full-term normal infants. In the 3 immunodeficient children the results were as follows: Child 1 had a 2- to 3-fold decrease in ADA with normal PNP and AK activities; Child 2 had a 2- to 3-fold decrease in AK, 4-fold decrease in HGPRT with normal PNP and ADA activities; Child 3 had confirmed AIDS and a 4-fold decrease in ADA, 6-fold decrease in HGPRT with normal PNP activity. The possible role of these depressed purine enzyme activities found in lymphocytes is discussed in relation to the impaired immunity seen in these infants.