. . "Histamine, a natural molecule present in the body, and other molecules in the class known as histamine type-2, or H2, receptor agonists, bind to the H2 receptor on the phagocytes, temporarily preventing the production and release of oxygen free radicals. By preventing the production and release of oxygen free radicals, histamine based therapeutics may protect NK, T, and liver-type NK/ T cells. This protection may allow immune-stimulating agents, such as IL-2 and IFN-alpha, to activate NK cells, T cells and NK/ T cells more effectively, thus enhancing the killing of tumor cells or virally infected cells."@en . . . "investigational"@en . . . . . . . . . "HD-O"@en . . "Investigated for use/treatment in hepatitis (unspecified), hepatitis (viral, C), and liver disease."@en . . . . . . . . . . . . . "HD-O is an amine derived by enzymatic decarboxylation of histidine. It is a powerful stimulant of gastric secretion, a constrictor of bronchial smooth muscle, a vasodilator, and also a centrally acting neurotransmitter."@en . . . .