M. Ikeda et al., Serum amyloid A, cytokines, and corticosterone responses in germfree and conventional mice after lipopolysaccharide injection, BIOS BIOT B, 63(6), 1999, pp. 1006-1010
To determine why germfree mice are less susceptible to lipopolysaccharide (
LPS) than conventional mice, we studied serum levels of serum amyloid A (SA
A), tumor necrosis factor (TNF), interleukin 1 (IL-1), IL-6, and corticoste
rone in mice after treatment with LPS. A single injection of LPS caused an
elevation of SAA, an acute-phase protein in the mouse, in both conventional
and germfree IQI mice, and the response was significantly less in germfree
mice. LPS-induced elevations of serum TNF, IL-1, and IL-6 levels were also
significantly less in germfree mice, while serum corticosterone levels wer
e greater in germfree mice than in conventional mice. These results suggest
that the lower susceptibility to LPS and a smaller response of SAA elevati
on by LPS in germfree mice may result from less elevation in serum of these
cytokines in these mice, which are known to mediate the acute phase respon
se of SAA. High levels of serum corticosterone in germfree mice may be part
ly responsible for the lower responsiveness of these inflammatory cytokines
to LPS in these mice.