Expression of oncofetal antigens by murine and human normal cells in tissue culture

Normal mouse tissues in tissue culture express fetal antigens that are not expressed on these same tissues in vivo. The fetal antigens expressed on normal mouse cells in vitro are also expressed on at least two murine sarcomas, and account for the cross-reactive antibodies between these tumors. The fetal antigens are distinct from unique tumor-specific antigens found on these neoplasms. Normal human cells in tissue culture also express antigens found in human fetuses during the first trimester of pregnancy. Many human sera contain natural antibodies directed against the fetal antigens appearing in vitro. The expression of oncofetal antigens by normal cells in tissue culture must be taken into account in the interpretation of results of studies in tumor immunology in which tissue-cultured cells are utilized.