Anti-endotoxin antibodies directed against Escherichia coli R-1 oligosaccharide core-tetanus toxoid conjugate bind to smooth, live bacteria and smooth lipopolysaccharides and attenuate their tumor necrosis factor stimulating activity.

The reactivity of anti-OS R1-tetanus toxoid serum with various smooth and rough lipopolysaccharides have been determined in enzyme-linked immunosorbent assay (ELISA) and with intact, live smooth bacterial cells in flow cytometry. All tested smooth lipopolysaccharides of R1 core type belonging to nine different O-serotypes reacted strongly with anti-conjugate antibodies. Flow cytometry showed that anti-core antibodies labelled more than 95% of bacterial cells with high intensity of fluorescence. The anti-conjugate serum was able to react with free form of smooth lipopolysaccharides and to inhibit their TNF stimulation activity in in vitro and in vivo models.