The present invention provides a therapeutic or prophylactic agent for systemic inflammatory response syndrome (SIRS), which contains a polypeptide comprising an amino acid sequence the same or substantially the same as the amino acid sequence of the N-terminal domain of pentraxin 3 capable of binding to histone to form a polypeptide aggregate, or a pharmacologically acceptable salt thereof. The present invention also provides a reagent for quantification and a quantification method of histone, which utilize the polypeptide or a pharmacologically acceptable salt thereof. Furthermore, the present invention provides a polypeptide aggregate containing the polypeptide or a pharmacologically acceptable salt thereof and histone and a production method thereof.
