Expression of oncofetal antigens on murine sarcomas characterized for expression of endogenous MuLV

A rabbit antiserum raised by repeated immunization with BALB/c fetuses obtained at 10-14 days of gestation was used to search for oncofetal antigens (OFA) in murine sarcomas which had previously been characterized for the expression of endogenous murine leukemia virus (MuLV). Iodinated protein A from staphylococcus aureus (IPA) was used to quantitate binding of the antiserum to cultured tumor or fetal cells or to saline extracts of tumors and fetuses. Use of the "antigen" extracts facilitated the assay: the extracts bound to plastic and served as targets for the binding assay, eliminating the need to establish tumors in culture. After absorbtion in vitro and in vivo with adult tissues the rabbit antiserum bound to day 10-14 fetal cells and extract but not to endogenous MuLV (BALB virus 1). The antiserum bound equally well to MuLV-negative and MuLV-positive sublines of MCA-induced sarcomas 1420 and 1414 but not to Moloney sarcoma cells and MCA-induced sarcoma 1386. Thus, the absorbed antiserum detects a class of common cross-reacting antigens which are serologically distinct from MuLV-associated antigens.