Nanoparticles reveal permanent and reversible changes to lymph node biomechanics during inflammatory response

Area of Science:

• Immunology
• Biophysics
• Biomaterials Science

Background:

• Lymph nodes orchestrate adaptive immune responses by housing lymphocytes.
• Lymph node structure and material properties change during inflammation to accommodate cell proliferation.
• The biophysical properties of lymph nodes during inflammation are largely unexplored.

Purpose of the Study:

• To investigate the biophysical properties of lymph nodes during acute inflammation and resolution.
• To explore how lymph node biomechanics are affected by inflammatory stimuli.
• To determine if biological sex influences lymph node biomechanical changes during inflammation.

Main Methods:

• Utilized multiple particle tracking microrheology (MPT), a nanoparticle-based technique.
• Measured elastic/loss moduli, microviscosity, and pore size of lymph nodes post-inflammatory stimulus.
• Analyzed changes in extracellular matrix (ECM) materials.

Main Results:

• Lymph node biomechanical properties change during both the onset and resolution of acute inflammation.
• B and T cell rich areas showed similar biomechanical property changes over time.
• Biological sex significantly modulated lymph node biomechanics: female mice showed increased stiffness, while male mice showed decreased stiffness.
• Female lymph nodes exhibited permanent remodeling, maintaining higher stiffness post-inflammation, unlike male lymph nodes that returned to baseline.

Conclusions:

• Biophysical properties of lymph nodes are significantly altered during acute inflammation and resolution.
• Sex-specific biomechanical responses in lymph nodes during inflammation are a novel finding.
• Changes in biomechanical properties correlate with alterations in ECM materials, suggesting structure-function relationships.
• MPT is a robust technique for analyzing lymph node interstitial tissue properties and their response to inflammation.