( ( ( White ( blood cells ) ) ( -LRB- ( leukocytes -RRB- ) ) ) ( ( may ( be ( ( a sign ) ( of ( an infection ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NNP White) (NN blood) (NNS cells)) (PRN (-LRB- -LRB-) (NP (NNS leukocytes)) (-RRB- -RRB-))) (VP (MD may) (VP (VB be) (NP (NP (DT a) (NN sign)) (PP (IN of) (NP (DT an) (NN infection)))))) (. .)))
White blood cells (leukocytes) may be a sign of an infection.
(ROOT (S (NP (JJ Leukocytes) (NN blood) (NNS cells)) (VP (VBP are) (ADJP (JJ white))) (. .)))