Lysis of Tumor Cells by Antibody and Complement. I. Lack of Correlation Between Antigen Content and Lytic Susceptibility

Abstract

The Forssman antigen content of sheep red blood cells (SRBC) and cells derived from guinea pig hepatomas and livers of normal guinea pigs was compared by measuring the capacity of these cells to absorb hemolytically active IgM from antisera containing Forssman antibody. There was no significant difference in the absorption capacity for Forssman antibody between the SRBC, normal liver, and hepatoma cells. Two lines of guinea pig hepatomas, L1 and L10, were used. L1 and L10 cells differed in their susceptibility to lysisby Forssman antibody and complement (C). The difference could not be ascribed to variations in the antibody class of the hemolysin or in the concentration of Forssman antigen on the cell surface. L1 cells sensitized with Forssman antibody or specific antitumor antibody were Iysable by all C sources tested. Human C was more efficient in lysing L1 than rabbit and guinea pig C. L10 cells sensitized with IgM Forssman antibody were more resistant to lysisby human C than L1 cells and were not lysed by either guinea pig or selected rabbit C. L10 cells could be lysed efficiently with human C when sensitized with a specific anti-L10 antiserum. These experiments indicate that differences in antigen concentration are not sufficient to explain the variation in sensitivity to antibody complement-mediated lysis of these two tumor lines.