Two-stage cell wash process controlled by optical sensor

An apparatus for removing undesirable elements, not normally found in healthy whole blood, from blood mixed with the undesirable elements, the apparatus comprising:

• a rotatable centrifuge bowl for separating the blood into components according to relative densities of the components;
• a controllable pump for admitting wash solution into the centrifuge bowl;
• a port through which fluid exits the bowl:
• an optical sensor for monitoring said fluid exiting the bowl and generating an output signal indicative of a concentration of said undesirable elements in the exiting fluid;
• control means, operatively coupled to the pump, for comparing the concentration indicated by the output signal with a first predetermined concentration to determine, before actuating the pump to admit any wash solution into the bowl, at least one of:
• (a) a number of wash stages, wherein a wash stage comprises admitting a wash-stage volume of wash solution into the rotating centrifuge bowl and thereafter recombining said components;
• and
• (b) at least one wash-stage volume of wash solution, the control means operable for operating the pump so as to wash the blood in accordance with said determination.