Alpha fetoprotein: effect of heterologous antiserum on hepatoma cells in vitro

Hepatoma cells derived from The Jackson Laboratory mouse hepatoma BW7756 synthesized alpha fetoprotein (AFP) in vitro. The AFP was immunologically identical to that circulating in the sera of hepatoma-bearing mice. An in vitro cytotoxic effect of rabbit antiserum to AFP was studied in hepatoma cells obtained both from fresh cell suspensions and short-term cell culture. The use of intact and/or inactivated anti-AFP serum inhibited the growth of the AFP-producing cells. The cytotoxic effects of the antiserum depended on exposure time and serum concentration. The cytotoxicity was complement independent, as demonstrated by studies with heat-deactivated serum devoid of extrinsic complement. The control target cells included fresh cell suspensions of normal mouse liver and mouse muscle fibroblasts grown in short-term culture. Specificity of the antisera for the target cells was demonstrated by absorption with purified mouse AFP. The results could be explained by the presence of AFP on the hepatoma cell surface.