A novel cytotoxic mechanism against neuroblastoma (NB) cells based on natural immunoglobulin M serum antibodies is described. The occurrence of these antibodies, which are able to induce complement-mediated cytolysis of NB cells, has been investigated in several age groups of healthy persons and in patients with NB. The cytotoxicity of serum samples has been measured in terms of propidium iodide DNA incorporation using a FACScan. The prevalence of anti-NB 1gM antibodies shows a strong age dependence characterized by a nearly complete lack in the first year of life and a steep rise up to 82% beginning with the second year of life. In the sera of 11 NB-bearing patients no cytotoxicity has been found, despite the fact that 8 of these patients were older than 1 year. These findings lead to the hypothesis that natural 1gM antibodies could play a role as an immunological control mechanism against NB.
