Neutrophils Recirculate through Lymph Nodes to Survey Tissues for Pathogens

Area of Science:

• Immunology
• Cell Biology

Background:

• Lymph node function relies on lymphocyte recirculation.
• The role of neutrophils in lymph nodes at steady state is not well understood.

Purpose of the Study:

• To investigate neutrophil recirculation in lymph nodes.
• To determine the role of lymph node neutrophils in immune surveillance and response.

Main Methods:

• Utilized germ-free and cohoused mice models.
• Investigated neutrophil entry via L-selectin and exit via S1P-dependent mechanisms.
• Assessed neutrophil recruitment and swarm formation following Staphylococcus aureus infection.

Main Results:

• Identified neutrophils recirculating in lymph nodes at steady state.
• Demonstrated neutrophil entry via L-selectin and exit via S1P-dependent pathways.
• Showed that lymph node neutrophils act as reconnaissance cells, with LTB4 initiating recruitment of additional neutrophils, crucial for effective Staphylococcus aureus infection response.

Conclusions:

• Neutrophils possess the capacity for recirculation through lymph nodes, similar to lymphocytes.
• Steady-state lymph node neutrophils enhance immune readiness by facilitating rapid neutrophil recruitment and swarm formation during bacterial dissemination.