Multitier mechanics control stromal adaptations in the swelling lymph node

Area of Science:

• Immunology
• Cell Biology
• Biophysics

Background:

• Lymph nodes (LNs) are crucial for immune responses, exhibiting significant size increases upon immunological challenge.
• LNs consist of fibroblastic reticular cells (TRCs) forming immune cell niches and capsular fibroblasts forming the organ's outer shell.

Purpose of the Study:

• To investigate the biomechanics of lymph node swelling at both cellular and organ levels.
• To understand the roles of different fibroblast populations in regulating LN size changes during immune responses.

Main Methods:

• Characterization of cellular and organ-scale biomechanics during LN swelling.
• Analysis of lymphocyte trapping, proliferation, and resulting pressure forces.
• Investigation of TRC strain sensing, cell-matrix adhesions, and stromal network remodeling.
• Assessment of the fibrotic reaction in the organ capsule.

Main Results:

• Lymphocyte influx and proliferation generate outward pressure, stretching TRCs and their associated conduits.
• TRCs sense mechanical strain, initiating coordinated growth and remodeling of the stromal network.
• Following an initial relaxation phase, the TRC network readopts its configuration.
• A significant fibrotic reaction in the organ capsule limits further LN expansion.

Conclusions:

• Lymph node swelling is a multi-tiered mechanical process controlled by distinct fibroblast populations.
• TRCs and capsular fibroblasts play coordinated but distinct roles in managing LN size changes.
• Understanding these biomechanical processes offers insights into immune regulation and tissue remodeling.