Immunopharmacological properties of a protein-bound histamine metabolite

Histamine metabolite was prepared by incubating histamine dihydrochloride and diamino oxidase for 24 h at 37 degrees C. Radioactive histamine was used for monitoring the whole procedure and to select the best experimental protocol. Pharmacological activities of histamine are abolished by this procedure. Histamine metabolite was found to bind to the serum proteins, to inhibit the PHA response of mouse and human mononuclear cells and to accelerate mortality rates in tumor-bearing mice. Thin layer chromatography allowed separation of metabolite from histamine and from known imidazol-derived compounds. This is the first experimental evidence for immunological properties ascribed to a histamine metabolite.