The isolation and selected properties of blood monocytes.

A technique is described for the quantitative recovery of monocytes from horse blood by means of flotation on dense albumin solutions. Monocytes are concentrated in a surface pellicle along with a few lymphocytes which are then removed when the monocytes adhere to a glass surface. The in vitro cultivation of homogeneous populations of monocytes results in an increase in (a) cell size, (b) number of mitochondria, and (c) phase-dense granules of the centrosphere. The phase-dense granules are osmiophilic and acid phosphatase positive. Quantitative biochemical analysis during cultivation have revealed increased levels of cytochrome oxidase, acid phosphatase, arylsulfatase, and BPN hydrolase. In addition, glucose utilization and lactic acid production are stimulated under the same conditions. The uptake of both bacteria and colloidal gold is stimulated during in vitro cultivation. The phagocytic activity of cultured monocytes may be enhanced by a purified bacterial lipopolysaccharide. These data are consistant with the in vitro maturation of monocytes to macrophages, a cell with greater metabolic and functional potentional.