Presence in bovine fetal serum of the protein antigenically related to p65-tumor associated antigen: its isolation and polyclonal antibody production.

Monoclonal antibodies raised to the 65-kDa tumor-associated protein (p65) isolated from a human breast cancer cell line have been used to detect an antigenically related protein (p65-like) present in fetal bovine serum (FBS) by Western blot analysis. We have isolated the p65-like protein from FBS by isoelectrofocusing (IEF) on native gels followed by electrophoresis in 12.5% polyacrylamide gel containing 0.1% SDS (SDS-PAGE). Immunostaining with anti-p65 monoclonal antibody of fetal bovine serum fractions separated by electrophoresis on cellulose acetate membrane revealed that the p65-like protein had a location similar to one of gamma-globulin. This protein migrates as a single band upon electrophoresis in SDS-PAGE and had four isoforms which migrate as two doublets with pI's of approximately 5.0 and 5.3.