Immunodeficiency secondary to adenosine deaminase deficiency and purine nucleoside phosphorylation deficiency.

A deficiency of adenosine deaminase or purine nucleoside phosphorylase could theoretically cause immunodefiency because the nucleoside substrates for the enzymes are toxic to lymphocytes, or because the enzyme products are necessary for immune development. This issue was resolved by analyses of purine metabolites in the plasma and cells of adenosine deaminase and purine nucleoside phosphorylase deficient children, and by studying the effects of the enzyme substrates on lymphocyte function and survival