Sentence:  The cells were washed three times with saline , anti human serum was added , the <WSD>cells</WSD> were resuspended , and the mixture was centrifuged at 1000 rpm for 1 min and examined for agglutination . 
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