Systems and methods for filtering materials from biologic fluids are discussed. Embodiments may be used to filter cerebrospinal fluid (CSF) from a human or animal subject. The method may include the steps of withdrawing fluid comprising CSF, filtering the volume into permeate and retentate by passing the fluid through a tangential flow filter, and returning the permeate to the subject. During operation of the system, various parameters may be modified, such as flow rate.
