Notes on the peroxidase activity of human basophil leukocytes

In recent years, basophils have been described as peroxidase-positive in some textbooks (6, 8). However, as far as basophils in the peripheral blood from healthy persons are concerned, they must be considered as peroxidase-negative. This discrepancy is thought to be based on the following points: 1) fixation of human basophils is more difficult than that of the other leukocytes; 2) counterstaining with a certain basic dye causes misinterpretation of the enzyme reaction; 3) diaminobenzidine which has been most frequently used as hydrogen donor in the peroxidase reaction is so sensitive to non-enzymatic substances that substrate-minus experiments as well as inhibition experiments for peroxidase are absolutely necessary; and 4) basophils in the peripheral blood from healthy persons are originally peroxidase-negative. On the other hand, basophils in the peripheral blood from patients with myeloid leukemia are frequently peroxidase-positive, and yet, the peroxidase demonstrated in such basophils is not true myeloperoxidase since peroxidase from the above patients is resistant to heating, methanol and other chemicals known as inhibitors of myeloperoxidase. These data are illustrated by many color photographs.