(S (S (NP (BASENP (DT The) (NNS antibodies)) (SBAR (WHNP (WDT that)) (S (VP (VBP are) (VP (VBN produced) (PP (IN by) (BASENP (DT this) (NN reaction)))))))) (VP (MD may) (VP (VB account) (PP (IN for) (NP (BASENP (JJ sexual) (NN differentiation)) (PP (IN of) (BASENP (DT the) (NN brain)))))))) (PERIOD .))