Induction of release of cytotoxin from murine bone marrow cells by an animal lectin.

An animal lectin purified from loach (Misgurnus anguillicaudatus) eggs induced release of cytotoxin from fresh bone marrow cells from mice, although the other lectins tested, wheat germ agglutinin, concanavalin A, and phytohemagglutinin did not. The cytotoxin released from bone marrow cells was a heat-labile protein with a molecular weight of 70,000. The main cells responsible for release of Mr 70,000 cytotoxin seemed to be of macrophage lineage, since they adhered to plastic and were sensitive to certain antibodies for markers of macrophages. However, they did not express asialo GM1 antigen which is expressed by activated macrophages. Removal of cells that phagocytized iron did not diminish but rather enhanced the release of cytotoxin. Therefore, active bone marrow cells appeared to be immature, not mature macrophages. These data suggest that immature bone marrow cells that are not specifically activated have a cytolytic potency against tumor cells and that internal animal lectins may induce release of the cytotoxin from these cells.