CD16 ANTIGEN DENSITY ON NEUTROPHILS IN CHRONIC MYELOPROLIFERATIVE DISORDERS

Using flow cytometry, we quantitatively examined the density of the CD 16 (IgG Fe receptor III) antigen on neutrophils in healthy control sub jects, in patients with neutrophilia due to bacterial infection, and i n patients with chronic myeloproliferative disorders (chronic myeloid leukemia [CML], polycythemia vera, or essential thrombocythemia). The density was expressed as the mean fluorescence intensity of neutrophil s stained with fluorescein isothiocyanate-labeled anti-CD16 monoclonal antibody. We also determined leukocyte alkaline phosphatase activity semiquantitatively in the same population. The mean (+/- SD) density o f the CD16 antigen on neutrophils in patients with CML (n = 13; 240.4 +/- 134.8) was lower (P<.001) than in healthy control subjects (n = 25 ; 656.6 +/- 238.0), and the density was also lower than in patients wi th bacterial infection (n =15; 671.5 +/- 288.1), polycythemia vera (n = 7; 552.6 +/- 99.9), or essential thrombocythemia (n = 11; 671.5 +/- 411.5). The density of the CD16 antigen was 300 or more in an healthy control subjects and in all patients examined, except for those with C ML. The CD16 antigen density was less than 300 in 10 of the 13 patient s with CML. Leukocyte alkaline phosphatase activity was also low in 10 of the 13 patients with CML. These findings indicate that flow cytome tric analysis of the density of neutrophil CD16 antigen is useful for the differential diagnosis of CML from other chronic myeloproliferativ e disorders.