Vitamin B12 R-binder localization in the human uterus: an immunohistochemical study

The localization of vitamin B12 R-binder in the uterus was studied by use of an immunoperoxidase technique. Positive staining by anti-R-binder antiserum was observed in the columnar epithelium of the endocervix (18/18 cases) and in the surface epithelium of the endometrium (8/21 cases). Staining was usually seen in the apical portion of the epithelium; cytoplasmic staining in the endocervical columnar epithelium was intense. The secretory products in the endocervical glands showed positive staining. The endometrial glandular epithelium did not stain (0/24 cases). Metaplastic squamous epithelium of the endocervix showed positive staining (3/18 cases). The native squamous epithelium as well as the stromal components of the cervix, endometrium, and myometrium were negative for R-binder. This study shows that R-binder is localized in the uterus, especially in the endocervical glands. The R-binder in the endocervix may have antimicrobial activity in the uterus as in other organs, such as the intestines and mammary glands.