The influence of antisera specific for alpha-fetoprotein and mouse serum albumin on the viability and protein synthesis of cultured mouse hepatoma cells.

The cytotoxic potential of heterologous rabbit antibody directed against mouse serum albumin (MSA) and alpha-fetoprotein (AFP) was investigated in vitro with a cell line (Hepa) derived from the mouse hepatoma BW7756. Anti-AFP in the presence of complement could kill Hepa cells at concentrations of anti-MSA that were virtually nontoxic. The specificity of the anti-AFP was defined by demonstrating that Hepa cell toxicity was dependent upon and paralleled the secretion of AFP in synchronized cultures. Furthermore, neither antiserum could be shown to be significantly toxic to mouse neuroblastoma cells (Neuro-2A). Immunoglobulin purified from pools of antisera was also highly effective in producing cytotoxicity even in a complement-free system. This reaction proceeded more slowly, requiring nearly 48 hr to reach maximum effect in comparison to the 12 hr for complement-mediated toxicity. MSA and AFP are secreted during different phases of the cell cycle. In cultures arrested by isoleucine starvation, labeled AFP appears in the medium 10 hr after release of the blockade in association with S phase. The appearance of labeled MSA is delayed until the first mitosis. Cytotoxic effects of anti-AFP parallel the secretion of AFP in synchronous cultures. Both antisera could be inhibitory to the secretion and synthesis of the proteins of their antigenic specificity. MSA synthesis was more susceptible to this inhibition than was AFP synthesis. The significance of this phenomenon and its association with the differential cytotoxicity of the antiserum are discussed.