A System Dynamics Model to Predict the Human Monocyte Response to Endotoxins

Area of Science:

• Immunology
• Systems Biology
• Computational Biology

Background:

• The human immune system is a complex network susceptible to external stimuli.
• Lipopolysaccharides (LPSs) from bacteria can induce inflammatory responses and endotoxin tolerance (ET) in monocytes.
• Understanding ET is crucial for managing inflammatory diseases and sepsis.

Purpose of the Study:

• To develop a system dynamics model of LPS-induced inflammation and ET in human monocytes.
• To investigate the effects of varying LPS doses on monocyte response.
• To compare human monocyte responses to LPS with findings from animal models.

Main Methods:

• Developed a system dynamics model with two subsystems, six states, seven flows, and 14 parameters.
• Estimated and optimized model parameters using experimental data from human monocytes treated with LPS.
• Simulated monocyte responses to different LPS doses, including super-low doses.

Main Results:

• The model accurately reproduced LPS-induced inflammation and subsequent ET in human monocytes.
• Super-low-dose LPS stimulation in humans did not induce ET or enhance inflammatory response to a secondary challenge, differing from animal models.
• The model confirmed low tumor necrosis factor alpha (TNFα) production and increased C-C motif ligand 2 in the tolerant state.

Conclusions:

• The developed model provides insights into human monocyte responses to LPS and ET.
• Findings suggest differences in ET induction between human monocytes and animal models, particularly with low LPS doses.
• The model may aid in understanding sepsis and developing diagnostic or prognostic tools by analyzing monocyte-endotoxin interactions.