Assessment of Anti-Tumor Cytotoxic Activity of Naturally Occurring Antibodies in Human Serum or Plasma.

A small percentage of the Western population carries antibodies in the peripheral blood, which are able to kill human tumors such as neuroblastoma or melanoma. Several observations indicate that these antibodies, preferentially of IgM isotype, belong to the class of naturally occurring antibodies. Here, we describe two screening methods for the detection and quantification of such antibodies in human blood samples: a cellular ELISA technique and a flow cytometric assay, based on intercalation of fluorescent propidium iodide into the DNA of dying or dead cells.

Cytotoxic activity against human neuroblastoma and melanoma cells mediated by IgM antibodies derived from peripheral blood of healthy donors.

A small percentage of healthy donors identified in the Western population carry antibodies in their peripheral blood which convey cytotoxic activity against certain human melanoma and neuroblastoma cell lines. We measured the cytotoxic activity of sera and plasmas from healthy donors on the human neuroblastoma cell line Kelly and various melanoma cell lines. Antibodies of IgM isotype, presumably belonging to the class of naturally occurring antibodies, exerted cytotoxic activity in a complement-dependent fashion.