Susceptibility to and escape from complement-mediated lysis of guinea-pig hepatoma line-10

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Abstract
Rabbit xenoantisera produced against diethyl‐nitrosamine‐induced strain‐2 guinea‐pig hepatoma line‐10 cells (L‐10) according to various immunization schedules were compared for their cytotoxicity on L‐10 cells in the presence of guinea‐pig complement. The highest activity was obtained with anti‐sera (Cx‐1) produced by repeated intravenous injections of living L‐10 cells at high cell dosage, whereas intramuscular injections of living or glutaraldehyde‐treated L‐10 cells at similar frequency and cell dosage were less effective for the production of cytotoxic antibodies against L‐10 cells. Intravenous injections of smaller cell doses were less effective. The cytotoxic antibody in Cx‐1 antiserum was shown to be IgG by various methods including gel filtration on Sephadex G‐200, ion exchange chromatography and immunoelectrophoresis of purified tumor‐specific antibodies. It was concluded that L‐10 cells can be lysed by guinea‐pig complement and tumor‐specific antibodies (IgG). Some antisera contained IgM antibodies which were not cytotoxic. A decrease in susceptibility of L‐10 cells to complement‐mediated lysis was observed when the cells were maintained in vivo for a long period (more than 20 passage generations). This was due to a lower density of tumor antigens on the cell surface. When tumor cells were treated with a second antibody directed against rabbit IgG or F(ab′)2, cytotoxicity of Cx‐1 antisera was completely abolished.