Systems and methods for treating biologic fluids are disclosed. Some disclosed embodiments may be used to filter cerebrospinal fluid (CSF) from a human or animal subject, heat CSF to a target temperature, cool CSF to a target temperature, apply light treatment to CSF, separate cells via their dielectric properties, apply spiral and/or centrifugal separation, introduce additives to target particles, and/or apply combinations thereof. The method may include the steps of withdrawing fluid comprising CSF, treating the fluid, and returning a portion of the treated fluid to the subject. During operation of the system, various parameters may be modified, such as flow rate.