Restoration of in-vitro lymphocyte responses with exogenous adenosine deaminase in a patient with severe combined immunodeficiency.

Deficiency of adenosine deaminase (A.D.A.) occurs in an autosomal recessive form of severe combined immunodeficiency (S.C.I.D.). The role of this enzyme deficiency in the pathogenesis of the immune defects is not clear. A patient with A.D.A. S.C.I.D., studied during the first six weeks of life, was found to have B and T lymphocytes as well as 25% of normal lymphocyte responses to mitogens. This patient subsequently became severely lymphopenic with loss of mitogen responsiveness. Addition of calf-intestinal A.D.A. or human-erythrocyte A.D.A. to cultures of this patient's lymphocytes restored their ability to proliferate when stimulated with mitogens. These data indicate that A.D.A. deficiency is causally related to the cellular immune defects observed in A.D.A. S.C.I.D. and suggests a possible role for enzyme replacement in the therapy of this disorder.