Production of alpha-fetoprotein by human submandibular gland.

Alpha-fetoprotein (AFP) is a 590 amino acid polypeptide that was initially defined as an embryonal serum globulin. The yolk sac endoderm, fetal liver and fetal gut were shown to be the main sites of AFP synthesis in the embryo (Gitlin and Boesman, J. Clin. Invest. 46: 1010-1016, 1967). AFP synthesis is still continued in human adults (Ruoslahti and Seppala, Int. J. Cancer 8: 374-383, 1971) although the physiological level of serum AFP is lower than 10 ng/ml. AFP was also demonstrated in certain tumors and in various diseases or conditions such as yolk sac tumor, hepatoma, hepatoblastoma, acute and chronic liver cirrhosis, pregnancy and so on (Abelev, Adv. Cancer Res. 14: 295-358, 1971; Ruoslahti and Seppala, Cancer Res. 29: 275-346, 1979). Salivary glands have not been implicated in AFP synthesis. We investigated the expression of AFP in normal human salivary glands by immunohistochemistry with a monoclonal antibody against AFP, and documented immunoreactivity in intercalated and striated ducts of adult human submandibular glands.