Flow cytometric analysis of macrophage heterogeneity and differentiation: utilization of electronic cell volume and fluorescent substrates corresponding to common macrophage markers.

We have utilized electronic cell volume (ECV) and several fluorescent analogues of traditional macrophage markers in a flow cytometric characterization of macrophage heterogeneity. With this technique, various features of macrophage differentiation and activation can be determined on as few as 10,000 cells per assay. Quantitations of cell volume, phagocytosis, RNA, myeloperoxidase, acid phosphatase, and the ectoenzyme leucine aminopeptidase have been carried out on cultured human monocytes and peritoneal macrophages. Quantitations of the amount of a particular marker on a per cell basis, as well as population distributions, are of particular value in characterizing the heterogeneity in resident and inflammatory macrophages and the temporal relationships between different markers during macrophage activation and differentiation. This technique will facilitate a sophisticated analysis of monocyte-macrophage development by permitting the simultaneous analysis of a number of these features. In this way the interrelationships between different macrophage markers can be quantitated at the single cell level.