Studies on monocytes in acute leukemia I. Absolute monocyte count and staining characteristics of monocytes to α-naphthyl butyrate esterase

Using α-naphthyl butyrate esterase (α-NBE) staining, the absolute monocyte count was examined in 30 patients with acute leukemia. The absolute monocyte count in the peripheral blood was significantly low (33.5±30.5/μl) in untreated cases, but near normal (268.0±88.5/μl) in remission cases (normal subjects, 268.0±102.0/μl). There was an inverse correlation (r=-0.63, p<0.01) between the percentage of leukemic cells in the bone marrow and the peripheral monocyte count. Peripheral monocytes were cytochemically classified into 3 types according to α-NBE staining; namely, monocytes slightly, moderately and heavily stained were classified into Type I, Type II and Type III, respectively. In normal subjects the percentage of Type I monocytes was 9.8±6.3%; Type II, 28.6±8.7% and Type III, 59.7±12.6%. Type I monocytes were predominat in untreated acute leukemia, while the populations of monocytes retured to normal in remission. some relapsed cases showed not only a low absolute monocyte count, but also a high proportion of Type I and Type II monocytes before the clinical features of the relapse were apparent. Changes in the absolute monoyctes count and the staining behavior of monocyte to α-NBE are thought to reflect the clinical course of acute leukemia and to be useful for the early recognition of relapse. Quantitative and qualitative changes in monocytes are one possible cause of the increased susceptibility to infection of acute leukemia patients.