Deficiency of adenosine deaminase not associated with severe combined immunodeficiency.

The 12-year-old Kung (""Bushman'') boy from South West Africa who has marked deficiency of red cell adenosine deaminase has been found to have 2 to 3% of enzyme activity in red blood cells, 10 to 12% in leukocytes, and 10 to 30% in cultured fibroblasts. The enzyme has ADA 1 electrophoretic mobility: SV40 transformation of cultured fibroblasts caused a decrease of ""tissue ADA'' and an increase in ""red cell ADA'' isozymes. A battery of investigations revealed that the child has normal humoral and cellular immunity. A family study showed that a sibling had the same level of red cell ADA and the parents had intermediate levels. Studies of the Kung population from which the child comes have shown that the allele responsible for the condition, and which we designate ADA8, is polymorphic.