Three specimens of localized
amyloidosis of the seminal vesicle surgically removed for
prostatic cancer were immunohistochemically analyzed to clarify the nature of the
permanganate-sensitive congophilic subepithelial deposition. A variety of known amyloidogenic substances and secretory products in the seminal fluid were screened using the indirect immunoperoxidase method. In addition to reactivities with
antibodies to
amyloid P component and human seminal plasma, the
amyloid material was immunoreactive for
lactoferrin using a rabbit antiserum and two of three mouse
monoclonal antibodies. All the
antibodies labeled some of the normal seminal vesicle epithelial cells for this ironbinding, bacteriostatic
glycoprotein. In the prostate without accompanying
amyloid deposition, a considerable proportion of the glandular epithelium and secretory material were positive for
lactoferrin. Pre-embedding immunoelectron microscopy showed
lactoferrin immunoreactivity on the
amyloid fibrils. Focal staining of the
amyloid for gross cystic disease fluid protein-15 was also observed in two lesions. These findings strongly suggest that
lactoferrin is the major constituent in localized senile
amyloidosis of the seminal vesicle.