Schematic drawings of the LeukoCatch system and its usage. (A) Structure of the LeukoCatch system in which the stacked filters are installed between the stoppers at the bottom of a commercially available syringe. An enlarged view of the stacked configuration of the filtering system is shown in an inset. (B) A schematic drawing for a protocol for preparation of leukocyte (or PBMC) extract from 2 ml blood sample. The protocol consists of three procedures: capture of leukocyte by the LeukoCatch filters (i), leukocyte wash by PBS (ii), and collection of leukocyte extract in the elution buffer of the flow-through. (iii) The leukocyte extract in the flow-through fraction is ready for examination (e.g., by western blot analysis or ELISA). Thin horizontal arrows show the flow of the procedure (from step a, to step j). Thick vertical arrows indicate the multiple movements of the piston to allow the blood (i), PBS (ii) or elution buffer (iii) pass through the stacked filters in the LeukoCatch system. In each step, the piston was moved up (steps a, c, e, g and i) or down (steps b, d, f, h and i) by hand. The whole procedure may be completed within 3 min.