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 x 10(9) peripheral blood mononuclear cells could be separated in isotonic media to yield 6--8 x 10(8) lymphocytes with 95% purity and 1.5--2.5 x 10(8) 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) had a modal volume of 378 micrometer 3 while 10% were within the modal volume of the lymphocytes, 131 micrometer 3. 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.