Bacteroides lipopolysaccharides (LPS) induce anaphylactoid and lethal reactions in LPS-responsive and -nonresponsive mice primed with muramyl dipeptide.

Lipopolysaccharides (LPS) (100 micrograms/mouse) from Bacteroides gingivalis elicited anaphylactoid reactions in N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP) (100 micrograms)-primed C3H/HeN mice 0-48 h after MDP injection. The reaction resulted in death within 1 h when the LPS was injected 2-10 h after the MDP injection. LPS prepared from other Bacteroides and Salmonella species but not from others, including Escherichia coli, could induce the reaction. LPS-nonresponsive C3H/HeJ and C57BL/6 and C57BL/10 strains were also responsive to the reaction, while AKR, BALB/c, DBA/2, and ICR mice were not. By contrast, Bacteroides LPS exhibited weak lethal toxicity compared with E. coli LPS in galactosamine-sensitized C3H/HeN mice, while neither LPS had activity in C3H/HeJ mice. LPS from E. coli and Bacteroides intermedius induced serum tumor necrosis factor (TNF) activity in MDP-primed mice, except for C3H/HeJ mice; B. gingivalis LPS rarely induced TNF in C3H/HeN or C3H/HeJ mice, indicating no involvement of TNF in the anaphylactoid reaction. Serotonin could substitute for MDP for the reaction, and methysergide, a serotonin antagonist, inhibited the activity.