Methods and systems for processing and washing a photopheresis mononuclear cell product

A method for treating a cellular product in a cell therapy comprising:

• a) collecting a desired cellular product from a source of a biological fluid including desired cells in a unitary disposable fluid circuit mounted on a reusable hardware unit comprising a separator, valves, pumps, weight scales and sensors;
• b) combining said cellular product with a conditioning solution in an amount effective to arrive at a desired dilution of the collected cell product for said treatment within said fluid circuit;
• c) combining said cellular product with a treating agent in an amount effective for said cell treatment within said fluid circuit;
• d) treating said cellular product to arrive at a treated product in a treatment container;
• e) combining said treated product of step (d) with whole blood to arrive at a combined treated product and whole blood;
• f) introducing said combined treated product and whole blood into a separator chamber of said separator;
• g) separating a supernatant fraction from said combined treated product and whole blood within said separator to arrive at a combined cellular fraction and a supernatant fraction;
• h) establishing an optimal interface between said combined cellular fraction and said supernatant fraction;
• i) positioning said interface such that substantially all of said supernatant fraction exits said separator chamber to the substantial exclusion of said combined cellular fraction;
• and
• j) substantially maintaining said position by fixing flow of said combined treated product and whole blood into said separation chamber and/or adjusting flow of said supernatant fraction exiting the separation chamber.