A sterile cylinder containing an adsorptive carrier (e.g., cellulose acetate beads) for the adsorption of select leukocytes (e.g., granulocytes and monocytes/macropahges and mostly excluding lymphocytes, or the reverse) during apheresis. It is placed in an extracorporeal, closed-circuit apheresis system where blood is pumped from the patient, through the cylinder, and then back to the patient devoid of select leukocytes. It is typically used to treat a leukocyte-mediated condition [e.g., chronic inflammatory diseases such as inflammatory bowel disease (IBD) or rheumatoid arthritis (RA)] or to harvest select leukocytes. This is a single-use device.