Plasma constituents regulate LPS binding to, and release from, the monocyte cell surface

Area of Science:

• Immunology
• Microbiology
• Biochemistry

Background:

• Innate immunity uses pathways to respond to lipopolysaccharide (LPS) from Gram-negative bacteria.
• LPS triggers host cell activation via CD14 and Toll-like receptor 4.
• LPS is deactivated by sequestration into plasma lipoproteins.

Purpose of the Study:

• To investigate the connection between LPS-host cell interaction and LPS-lipoprotein sequestration.
• To elucidate the mechanism of LPS transfer between host cells and plasma lipoproteins.
• To determine the role of this transfer in modulating host immune responses.

Main Methods:

• Experiments utilizing human plasma and monocytes.
• Analysis of LPS binding and release dynamics.
• Assessment of cellular responses to LPS.

Main Results:

• LPS transiently binds to monocyte surfaces before transferring to plasma lipoproteins.
• Soluble CD14 enhances LPS release to lipoproteins; other proteins do not.
• LPS transfer to lipoproteins correlates with reduced cellular activation.
• Plasma changes post-trauma/sepsis alter LPS binding and release rates.

Conclusions:

• A novel pathway connects LPS-host cell activation and LPS-lipoprotein deactivation.
• LPS movement from leukocytes to lipoproteins attenuates host responses.
• This mechanism may play a significant role in regulating immune responses during infection and critical illness.