ABSTRACT
The discovery of the association between adenosine deaminase (ADA) (EC 3.5.4.4) deficiency and severe combined immunodeficiency disease in the early 1970s [1] provided exciting evidence of metabolic causation of immunodeficiency. This established a relationship between the metabolism of purines and developmental immunobiology, and this was reinforced by the discovery of purine nucleoside phosphorylase deficiency.
