A method and system for processing particles contained in a liquid biological sample is presented. The method uses a rotatable vessel for processing particles contained in a liquid biological sample. The rotatable vessel has a longitudinal axis about which the vessel is rotatable, an upper portion having a top opening for receiving the liquid comprising the particles, a lower portion for holding the liquid while the rotatable vessel is resting, the lower portion having a bottom, and an intermediate portion located between the upper portion and the lower portion, the intermediate portion having a lateral collection chamber for holding the liquid while the rotatable vessel is rotating. The method employs dedicated acceleration and deceleration profiles for sedimentation and re-suspension of the particles of interest.