Adenosine Deaminase Activity in Peripheral Lymphocytes of Psoriasis and Sézary's Syndrome

Adenosine deaminase (ADA) activity in peripheral lymphocytes were measured in 15 normal subjects, 15 psoriatic patients, and one patient with Sézary's syndrome. No significant differences were found in ADA activity between normal and psoriatic lymphocytes. A significant increase in ADA activity was observed in lymphocytes from the patient with Sézary's syndrome. The increased ADA activity in Sézary's syndrome was not accompanied by a change in the Km value for adenosine. The possible significance of the elevation of ADA activity in T‐lymphocyte dysfunction was discussed.