Collection of mononuclear cells and peripheral blood stem cells

A fluid processing system, comprising:

• a centrifuge configured to receive a separation chamber of a fluid processing assembly;
• a plurality of pumps configured to convey fluids through the fluid processing assembly;
• and
• a controller configured to
• actuate at least one of the plurality of pumps to convey blood into the centrifuge via an inlet,
• actuate the centrifuge to separate the blood in the centrifuge into a red blood cell layer, a plasma constituent, and a mononuclear cell-containing layer,
• actuate at least one of the plurality of pumps to convey a portion of the plasma constituent from the centrifuge via a plasma outlet and to convey a first portion of the red blood cell layer from the centrifuge via a red blood cell outlet while allowing a volume of the mononuclear cell-containing layer to increase in the centrifuge,
• actuate at least one of the plurality of pumps to convey a second portion of the red blood cell layer from the centrifuge via the red blood cell outlet to a red blood cell collection container of the fluid processing assembly,
• actuate at least one of the plurality of pumps to convey at least a portion of the contents of the red blood cell collection container to the centrifuge to convey at least a portion of the mononuclear cell-containing layer out of the centrifuge via the plasma outlet for collection, and
• actuate at least one of the plurality of pumps to convey plasma from the centrifuge via the plasma outlet to more fully collect said at least a portion of the mononuclear cell-containing layer without the use of collected plasma.