Isolation and enumeration of peripheral blood monocytes

Monocytes were isolated by counterflow contrifugation from human peripheral mononuclear cells obtained from whole blood by the Ficoll-Hypaque technique. Examination of volume spectra of the monocytes showed a bimodal distribution with peaks at 330 and 370 micron3. The upper peak contained 61.4 +/- 3.3% of the total monocyte population, whereas the remainder were in the lower peak which overlaps the lymphocyte spectrum. The purity of the monocyte preparations from six normal adult donors, identified by peroxisomes observed by electron microscopy, was 90.4 +/- 1.6%.