A system for washing a cellular product in a cell therapy comprising: a) a first reusable hardware unit comprising; a separator, one or more pumps, one or more valves and a sensing unit for monitoring an interface between treated mononuclear cells and supernatant; a controller configured to selectively operate said one or more pumps, one or more valves based on information obtained from said sensing unit and for withdrawing treated mononuclear cells from a container of treated mononuclear cells and introducing the treated mononuclear cells to said separator, wherein said controller is further configured to adjust the pumps and thereby the interface between treated mononuclear cells and supernatant to a more optimal position when the sensing unit senses that the location of the interface between said treated mononuclear cells and said supernatant is outside of the optimal position; b) a second reusable hardware unit comprising at least one light source and a chamber positioned in a field of light emitted by said at least one light source, said chamber configured to receive a container of cellular product; and c) a disposable fluid circuit mountable on said first reusable hardware unit and attachable to said second reusable hardware unit, said circuit including a venipuncture needle, a container for receiving a supernatant fraction of a treated mononuclear cells and at least one chamber associated with said separator for separating said treated separated mononuclear cell fraction from said supernatant fraction, and ports associated with said at least one chamber for diverting said mononuclear cell fraction to said venipuncture needle and for diverting said supernatant fraction to said container, said fluid circuit including tubing defining a flow path from said port to said container wherein said tubing is mated with one of said one or more pumps and wherein said controller is further configured to selectively rotate said one of said one or more pumps to effect the rate of flow of said supernatant fraction through said flow path in response to said information about the location of said interface from said sensing unit. a) a first reusable hardware unit comprising; a separator, one or more pumps, one or more valves and a sensing unit for monitoring an interface between treated mononuclear cells and supernatant; a controller configured to selectively operate said one or more pumps, one or more valves based on information obtained from said sensing unit and for withdrawing treated mononuclear cells from a container of treated mononuclear cells and introducing the treated mononuclear cells to said separator, wherein said controller is further configured to adjust the pumps and thereby the interface between treated mononuclear cells and supernatant to a more optimal position when the sensing unit senses that the location of the interface between said treated mononuclear cells and said supernatant is outside of the optimal position; b) a second reusable hardware unit comprising at least one light source and a chamber positioned in a field of light emitted by said at least one light source, said chamber configured to receive a container of cellular product; and c) a disposable fluid circuit mountable on said first reusable hardware unit and attachable to said second reusable hardware unit, said circuit including a venipuncture needle, a container for receiving a supernatant fraction of a treated mononuclear cells and at least one chamber associated with said separator for separating said treated separated mononuclear cell fraction from said supernatant fraction, and ports associated with said at least one chamber for diverting said mononuclear cell fraction to said venipuncture needle and for diverting said supernatant fraction to said container, said fluid circuit including tubing defining a flow path from said port to said container wherein said tubing is mated with one of said one or more pumps and wherein said controller is further configured to selectively rotate said one of said one or more pumps to effect the rate of flow of said supernatant fraction through said flow path in response to said information about the location of said interface from said sensing unit.