[Adenosine deaminase activity in blood cells; influence of cytostatic therapy in patients with acute leukemia and with renal transplants (author's transl)].

: A causal relation between the enzyme, adenosine deaminase (ADA), and immune dysfunction is well known: patients with congenital inactivity of ADA invariably suffer of severe combined immunodeficiency. In contrast, we found in patients treated with immunosuppressive drugs increased ADA enzyme activity. Previous findings on ADA activity in acute leukemias are until now controversial. We found normal to increased ADA activity in children with acute lymphatic leukemia (ALL) and acute myeloid leukemia (AML) in remission as long as they were treated with cytostatic drugs. In the group of cured leukemics (in continuous remission after suspension of the therapeutic regimen) the ADA activities were normal. These findings do not exclude a heterogeneity within the leukemia group. They do not explain the signs of cellular immunodeficiencies well known in patients with acute leukemias.