(S (S (BASENP (PRP He)) (VP (VBZ suggests) (SBAR (IN that) (S (BASENP (DT each) (JJ male) (NN foetus)) (VP (VP (VBZ prompts) (BASENP (DT a) (ADJP (RB progressively) (JJR stronger)) (NN immune) (NN reaction))) (PP (IN in) (NP (BASENP (DT the) (NN mother) (POS 's)) (NN body)))))))) (PERIOD .))