Histochemical study of leucine aminopeptidase in leukemia

By means of a histochemical method, the leucine aminopeptidase activity was studied in human normal and leukemic peripheral blood. Before administration of cytostatics the enzymic activity was high in the cytoplasm of blasts and in the nuclei of segmented cells. After therapy the activity of leucine aminopeptidase in blasts decreased, while in polymorphs it became negative in nuclei and positive in their cytoplasm. The non-granular leukocytes and platelets displayed a weak enzymic activity both in normal and malignant blood cells. The erythrocytes were negative.