( ( ( ( ( ( Organs , ) cells ) , ) and ) proteins ) ( ( constitute ( ( ( ( the system ) and ) antigens ) ( are ( ( the ( ( molecules and ) organisms ) ) ( ( to which ) ( it responds ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NNS Organs)) (, ,) (NP (NNS cells)) (, ,) (CC and) (NP (NNS proteins))) (VP (VBP constitute) (SBAR (S (NP (NP (DT the) (NN system)) (CC and) (NP (NNS antigens))) (VP (VBP are) (NP (NP (DT the) (NNS molecules) (CC and) (NNS organisms)) (SBAR (WHPP (TO to) (WHNP (WDT which))) (S (NP (PRP it)) (VP (VBZ responds))))))))) (. .)))
Organs, cells, and proteins constitute the system and antigens are the molecules and organisms to which it responds.
(ROOT (S (NP (NNPS Proteins)) (VP (VBP are) (NP (NP (JJ complex) (JJ organic) (NNS molecules)) (SBAR (WHNP (WDT that)) (S (VP (VBP make) (PRT (RP up)) (NP (NNS cells))))))) (. .)))