FLOW CYTOMETRIC MEASUREMENT OF NONSPECIFIC ESTERASE-ACTIVITY

alpha-Naphthyl acetate esterase (alpha-NAE) is primarily found in mono nuclear phagocytes and may be used to distinguish them from other leuc ocytes. Conventional cytochemical techniques are subjective and may be difficult to interpret, especially with cells which express only low levels of activity. This has caused difficulties in the classification of non-lymphoblastic leukaemias. This paper describes the adaptation of a cytochemical assay for use with the flow cytometer. The alpha-NAE activity of peripheral blood mononuclear cells was examined and found to be associated with the expression of the surface antigen CD14. The reaction could be inhibited by sodium fluoride. A series of human cel l lines were also compared for alpha-NAE activity. Distinct difference s in staining observed between the cell lines correlated with the numb er of cell-associated granules observed under the microscope.