Isolation of human monocytes on re-orienting gradients of percoll

We have developed a rapid and simple method for isolating monocytes from peripheral blood. After mononuclear cells are isolated on a Ficoll-Hypaque gradient, the monocytes are purified by sedimentation for 5 min through a re-orienting gradient of Percoll. The method is easily reproducible and yields approximately half of the monocytes in starting blood, with minimal contamination by lymphocytes. Although both monocytes and lymphocytes have similar densities, separation occurs because these cells migrate at differing rates through the gradient to reach their equilibration point.