Isolation of human monocytes by rosetting with antibody coated human erythrocytes and isopycnic gradient centrifugation.

Human erythrocytes O,Rh+ (D) coated with hyperimmune human anti-serum formed rosettes primarily with monocytes in peripheral blood mononuclear cell suspensions. The rosetting cells (EAhu-FRC), separated on a Lymphoprep gradient were found in the pellet and were up to 95% pure monocytes as judged by cytochemical criteria. A two step procedure involving depletion of T lymphocytes followed by the isolation of EAhu-RFC yielded monocytes up to 98% pure. The isolated cells did not respond to mitogens in vitro, but they act as accessory cells in mitogen-induced T lymphocyte proliferation. This simple method may be useful in studying monocyte function in human disease as it does not require a large amount of blood.