Apparatus, systems and methods for processing a blood sample. One embodiment comprises an isolation container having at least one sidewall defining an interior volume. The interior volume includes a medial reservoir in fluid communication with proximal and distal reservoirs. The diameter of the medial reservoir is less than the diameter of the proximal and distal reservoirs. Therefore, the isolation container has an interior volume which is roughly hour-glass shaped with the medial reservoir being a substantially narrowed portion or channel between two wider portions. The isolation container is configured such that the buffy coat layer of fractionated blood will be located within and may be accessed from the reduced cross sectional medial reservoir after a centrifuge or other processing step.