Abstract: Systems and methods are provided separating a first group of cells from a mixture of at least first and second groups of cells in a suspending fluid. The system includes an annular flow channel and at least one magnetic element positioned around the exterior of the annular flow channel as to provide a radially symmetric magnetic field around at least a portion of the annular flow channel. The at least one magnetic element is configured to provide a gradually increasing magnetic field along the axis of flow as to limit the maximum magnetic gradient within the annular flow channel. A pump is operatively connected to a terminal end of the annular flow channel to force the suspending fluid through the annular channel.