L-selectin levels of monocytes in whole blood, mononuclear/pre-elutriation fraction, and elutriated monocytes. Dreg-56 FITC was used to label L-selectin on monocytes. Monocytes treated with chymotrypsin (0.4 U/10⁶ cells) for 10 minutes at 25°C were used for background fluorescence as shown by a solid line. L-selectin on monocytes in whole blood is indicated by a bold solid line. L-selectin levels on pre- (solid dashes) and post-elutriation monocyte fractions (dotted line) were almost identical.