Prevention of lethal endotoxemia in actinomycin D-sensitized mice by incubation of Salmonella minnesota R595 lipopolysaccharide with monoclonal antibodies to R595.

Murine monoclonal antibodies reacting with lipopolysaccharide (LPS) of Salmonella minnesota strain R595 (Re chemotype) were prepared, and tested for their ability to protect actinomycin D-sensitized mice against lethal endotoxemia. Protection was found with some antibodies up to a 90-fold increase in LD50, whereas others exhibited no protection. The various protective antibodies did not all bind to the same epitope. The same applied for non-protective clones. Protective and non-protective clones could not be discriminated by ELISA. One protective monoclonal antibody (clone 20) was specific for ketodeoxyoctonate, a structural element common to various LPS. These findings show that the involvement of lipid A in the binding site of monoclonal antibodies is no prerequisite for protection.