( ( The spleen ) ( ( ( is ( an ( important area ) ) ) ( because ( it ( ( ( ( filters and ) removes ) ( defective ( T cells ) ) ) ( from ( the blood ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN spleen)) (VP (VBZ is) (NP (DT an) (JJ important) (NN area)) (SBAR (IN because) (S (NP (PRP it)) (VP (VBZ filters) (CC and) (VBZ removes) (NP (JJ defective) (NNP T) (NNS cells)) (PP (IN from) (NP (DT the) (NN blood))))))) (. .)))
The spleen is an important area because it filters and removes defective T cells from the blood.
(ROOT (S (NP (NP (DT The) (JJ main) (NN function)) (PP (IN of) (NP (DT the) (NN spleen)))) (VP (VBZ is) (S (VP (TO to) (VP (VP (VB filter) (NP (DT the) (NN blood))) (CC and) (VP (VB remove) (NP (JJ unwanted) (JJ red) (NN blood) (NNS cells))))))) (. .)))
The main function of the spleen is to filter the blood and remove unwanted red blood cells.