Streptococcus mitis cell walls and lipopolysaccharide induce lethality in D-galactosamine-sensitized mice by a tumor...

Area of Science:

• Immunology
• Microbiology
• Pathology

Background:

• Lipopolysaccharide (LPS) from Gram-negative bacteria is a potent inducer of inflammatory responses.
• The role of Gram-positive bacterial components in inducing similar inflammatory responses requires further investigation.

Purpose of the Study:

• To investigate the in vitro and in vivo effects of purified cell walls from Streptococcus mitis.
• To compare the inflammatory and toxic effects of Gram-positive cell walls with LPS.

Main Methods:

• Incubation of whole blood from LPS-sensitive and LPS-resistant mice with purified Streptococcus mitis cell walls.
• Administration of Streptococcus mitis cell walls or LPS to D-galactosamine-sensitized mice.
• Assessment of lethality and histopathophysiological changes.
• Evaluation of the effect of anti-tumor necrosis factor antibodies.

Main Results:

• Streptococcus mitis cell walls induced tumor necrosis factor (TNF) in vitro in whole blood from both LPS-sensitive and LPS-resistant mice.
• Purified cell walls were as effective as heat-killed bacteria in causing lethal shock in D-galactosamine-sensitized mice.
• Anti-TNF antibodies significantly suppressed the lethality induced by cell walls.
• Histopathological findings were indistinguishable between mice challenged with LPS and those challenged with Gram-positive cell walls.

Conclusions:

• Purified cell walls of Streptococcus mitis are potent inducers of TNF and lethal shock.
• The toxic effects of Gram-positive cell walls are mediated by TNF, similar to LPS.
• Gram-positive bacterial components can elicit responses comparable to LPS, impacting host defense and pathology.