Comparison of monocyte separation methods using flow cytometric analysis.

We isolated normal, nonactivated human monocytes from peripheral blood by four different methods: (1) rosetting with sheep erythrocytes pretreated with 2-aminoethylisothiouronium bromide hydrobromide (AET) followed by monoclonal antibody (OKT3 (CD3), B1 (CD19), Leu7, Leu11 (CD16] and complement treatment; (2) adherence to gelatin/plasma-coated flasks; (3) adherence to plastic dishes; and (4) separation by the Sepracell technique. We monitored these monocyte separations by determining cell recoveries, OKT4A+ lymphocyte contamination, monocyte binding to human immunodeficiency virus (HIV), number of non-specific esterase-positive cells, and proportion of mononuclear cells reactive with a battery of monoclonal antibodies specific for monocytes. Our results indicate that of the four methods compared, adherence to gelatin/plasma-coated flasks produced the highest purity, recovery, and satisfactory binding to HIV with the fewest contaminating CD4+ T cells.