Purification of human monocytes: Isolation and collection of large numbers of peripheral blood monocytes

Monocytes from human peripheral blood were purified by elutriation centrifugation. Up to 1.5 × 10⁹ peripheral blood mononuclear cells could be separated in isotonic media to yield 6–8 × 10⁸ lymphocytes with 95% purity and 1.5–2.5 × 10⁸ monocytes with greater than 90% purity. The temperature at which elutriation was performed determined the purity of the monocyte fraction. Both the lymphocyte and monocyte fractions were characterized by cell sizing and histochemical staining. Most of the myeloperoxidase positive mononuclear cells (monocytes) has a modal volume of 378 μm³ while 10% were within the modal volume of the lymphocytes, 131 μm³. Thus, there are two populations of cells with histochemical properties of monocytes which are separable by size. The collection and isolation of human peripheral blood monocyte populations in large numbers will facilitate studies of their functional characteristics.