N‐Alkaline Phosphatase: a Potential Disease Marker for Lymphoproliferative Disorders

Summary. A characteristic alkaline phosphatase (orthophosphoric monoester hydrolase, alkaline pH optimum, EC 3.1.3.1) was detected in the sera of most patients with infectious mononucleosis, acute and chronic lymphatic leukaemia, non‐Hodgkin's lymphoma, Burkitt's lymphoma and nasopharyngeal carcinoma. The enzyme was also present in the sera of nine out of 26 patients with cancer of the cervix. N‐APase in these cases counted 30–100% of the total alkaline phosphatase activity. N‐APase was absent from the sera of healthy individuals and of patients with acute and chronic granulocytic leukaemia, breast cancer, colon cancer, rheumatoid arthritis, ulcerative colitis, systemic lupus erythematosis, hepatitis and obstructive jaundice. Only three of 22 patients with Hodgkin's disease showed N‐APase activity in the serum. In infectious mononucleosis the presence of N‐APase activity was well correlated with the clinical course. In 13 cases studied, the clinical improvement was associated with the decrease or disappearance of N‐APase activity. N‐APase activity could not be detected in white cells of acute myeloid leukaemic patients, nor in the cells of myeloid blastic crisis of chronic granulocytic leukaemia. It was present in the cells of lymphoid blastic crisis of chronic granulocytic leukaemia.