Natural antibodies directed against murine lymphosarcoma cells: variability of level in individual mice.

Natural anti-tumor antibodies (NAA) were revealed, by a complement-dependent cytotoxicity test on el4 lymphoma cells, in the serum of C3Hf but not of C57BL mice. Hybrids between the positive C3Hf and the negative C57Bl mice were NAA producers. Individual variability of NAA level was found in C3Hf and in the hybrids. The study of mice housed in the same or in different cages and of mice belonging to the same or to different litters demonstrated a randomly distributed variability. These observations seem to exclude environmental influences on the natural immune response or genetic mutations in the C3Hf strain with the appearance of variants with different NAA content. The NAA level was age-dependent with a peak around 20-24 weeks of age. Inoculum of lymphoma cells induced an increase in the NAA level both in C3Hf and in the hybrids but not in C57Bl mice which seem therefore incapable of making guinea-pig complement-fixing NAA. The individual variability of NAA level and the stimulating effect of tumor cells support a potential role of NAA in immunosurveillance of oncogenesis.