( B ( - ( ( cells ( are ( ( ( ( lymphocytes , ) ( produced ( in ( ( ( the ( bone ( ( marrow and ) spleen ) ) ) , ) ( that ( ( ( fight infection ) primarily ) ( by ( maturing ( into ( plasma cells ) ) ) ) ) ) ) ) ) ) , ) ( which ( secrete antibodies ) ) ) ) ) . ) ) )
(ROOT (FRAG (NP (NNP B)) (: -) (S (NP (NNS cells)) (VP (VBP are) (NP (NP (NNS lymphocytes)) (, ,) (VP (VBN produced) (PP (IN in) (NP (NP (DT the) (NN bone) (NN marrow) (CC and) (NN spleen)) (, ,) (SBAR (WHNP (WDT that)) (S (VP (VB fight) (NP (NN infection)) (ADVP (RB primarily)) (PP (IN by) (S (VP (VBG maturing) (PP (IN into) (NP (NN plasma) (NNS cells)))))))))))) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBP secrete) (NP (NNS antibodies)))))))) (. .)))
B- cells are lymphocytes, produced in the bone marrow and spleen, that fight infection primarily by maturing into plasma cells, which secrete antibodies.
(ROOT (S (NP (NNP Bone) (NNP marrow)) (VP (VP (VBZ is) (VP (VBN found) (PP (IN inside) (NP (JJ many) (NNS bones))))) (CC and) (VP (VBZ produces) (NP (NNS lymphocytes)))) (. .)))