Immunohistochemical localization of histaminase (diamine oxidase) in decidual cells of human placenta.

An immunohistochemical technique has been developed for the localization of histaminase (diamine oxidase) in human placenta. The procedure utilizes antibody to highly purified human placental enzyme prepared in rabbits. Histaminase is shown to be present in the cytoplasm of the decidual cells of the maternal placenta; the staining is specific and can be removed by preabsorption of the antisera with purified antigen. The present demonstration of histaminase in the maternal portion of placenta confirms previous biochemical data suggesting that the enzyme is not a fetal product in this tissue. This study also provides further evidence that the presence of histaminase in some human tumors and in normal tissues like kidney and intestine is the result of the expression of a mature and not a fetal genome.