( ( a decrease ) ( in ( ( ( ( the concentration ) ( of ( plasma proteins ) ) ) ( in ( the blood ) ) ) , ) ) )
(ROOT (NP (NP (DT a) (NN decrease)) (PP (IN in) (NP (NP (DT the) (NN concentration)) (PP (IN of) (NP (NN plasma) (NNS proteins))) (PP (IN in) (NP (DT the) (NN blood))) (, ,)))))
a decrease in the concentration of plasma proteins in the blood,
(ROOT (S (NP (DT The) (JJ complement) (NN system)) (VP (VBZ is) (NP (NP (DT a) (NN series)) (PP (IN of) (NP (NP (NNS proteins)) (VP (ADVP (RB constitutively)) (VBN found) (PP (IN in) (NP (DT the) (NN blood) (NN plasma)))))))) (. .)))