Sentence:  The red cells for the Rh antibody tests were used within 3 days after drawing except for the * * f <WSD>cells</WSD> , which had been glycerolized and stored at - 20 ` C for approximately 1 year . 
Meaning of the word marked with <WSD> tags:  (biology) the basic structural and functional unit of all organisms; they may exist as independent units of life (as in monads) or may form colonies or tissues as in higher plants and animals