Abstract
A method was developed to demonstrate histonase activity in the cytoplasm of polymorphonuclear leukocytes, eosinophils and monocytes. The technique was based on the ability of flavianic acid (2,4-dinitro-l-naphthol-7-sulfonic acid) to form highly insoluble salts with arginine. Presumably, the source of the free arginine was from histone proteolysis as a result of the action of histonase.