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Endotoxin down-regulates T cell activation by antigen-presenting liver sinusoidal endothelial cells
P A Knolle1, T Germann, U Treichel
1First Medizinische Klinik und Poliklinik, Johannes Gutenberg Universität, Mainz, Germany. P.Knolle@zmbh.uni-heidelberg.de
Journal of Immunology (Baltimore, Md. : 1950)
|February 11, 1999
Summary
Endotoxin impairs liver sinusoidal endothelial cells' (LSEC) ability to present antigens, reducing immune responses. This occurs by affecting antigen processing and accessory molecule expression in LSEC, unlike other antigen-presenting cells.
Area of Science:
- Immunology
- Hepatology
- Cellular Biology
Background:
- Liver sinusoidal endothelial cells (LSEC) are crucial for clearing portal blood and present antigens.
- Endotoxin is present in portal blood and can influence immune cell function.
Purpose of the Study:
- To investigate the effect of endotoxin on the antigen-presenting function of LSEC.
- To understand the mechanisms by which endotoxin modulates LSEC accessory function.
Main Methods:
- Incubation of LSEC with physiological endotoxin concentrations.
- Measurement of CD4+ T cell IFN-gamma release.
- Analysis of antigen uptake, endosomal/lysosomal pH, and surface molecule expression (MHC class II, CD80, CD86).
Main Results:
- Endotoxin significantly reduced LSEC accessory function (>80%), unlike conventional antigen-presenting cells.
- Inhibition was linked to endosomal/lysosomal alkalinization and impaired antigen processing in LSEC.
- Endotoxin downregulated MHC class II, CD80, and CD86 expression on LSEC.
Conclusions:
- Endotoxin specifically impairs LSEC antigen processing and accessory molecule expression, down-regulating immune responses.
- This mechanism contributes to immune modulation within the hepatic microenvironment.