Staphylococcal culture supernates stimulate human phagocytes

Area of Science:

• Immunology
• Microbiology
• Pathophysiology

Background:

• Phagocytes are crucial for host defense against Staphylococcus and in Gram-positive septic shock.
• While mediators of Gram-negative sepsis are known (LPS), the key mediators in Gram-positive sepsis remain unidentified.
• Understanding these mediators is vital for developing targeted therapies.

Purpose of the Study:

• To investigate the interaction between soluble staphylococcal products and phagocytes.
• To identify potential mediators of Gram-positive sepsis beyond known toxins and endotoxins.
• To characterize the stimulatory effects of Staphylococcus aureus supernates on immune cells.

Main Methods:

• Harvesting Staphylococcus aureus supernates (SaS) from various strains.
• Assessing CD11b/CD18 expression upregulation on human neutrophils.
• Measuring TNF-alpha and IL-1 beta release from human monocytes.
• Conducting control experiments to exclude known staphylococcal components and endotoxins.
• Testing the heat stability of SaS activity.

Main Results:

• SaS significantly upregulated CD11b/CD18 on neutrophils, even at high dilutions.
• SaS induced the release of pro-inflammatory cytokines TNF-alpha and IL-1 beta by monocytes.
• Activity was heat-stable and not attributable to peptidoglycan, specific toxins, or endotoxins.
• SaS demonstrated higher potency in phagocyte stimulation compared to purified components or intact bacteria.

Conclusions:

• Soluble staphylococcal products, distinct from known mediators, are potent stimulators of phagocytes.
• These unidentified soluble factors likely play a significant role in the pathophysiology of Gram-positive sepsis.
• Further research is needed to identify these novel staphylococcal mediators.