Primed PMNs in healthy mouse and human circulation are first responders during acute inflammation

Area of Science:

• Immunology
• Cell Biology
• Hematology

Background:

• Polymorphonuclear neutrophils (PMNs) are key immune cells involved in inflammation.
• Existing methods may not fully capture the functional state of PMNs in circulation.

Purpose of the Study:

• To identify and characterize a distinct subset of PMNs with enhanced recruitment potential.
• To investigate the role of these primed PMNs in innate immunity and response to inflammation.

Main Methods:

• Utilized a novel fixation method to preserve native CD marker expression on PMNs.
• Employed immunophenotyping to distinguish between resting and primed PMN populations.
• Studied PMN dynamics in mouse models of acute inflammation and in human subjects.

Main Results:

• Identified a population of "primed for recruitment" PMNs (pPMNs) with high adhesion and activation markers.
• Observed rapid depletion of pPMNs from circulation and recruitment to inflamed tissues.
• Found that granulopoietic factors (GM-CSF, G-CSF) induce PMN priming.
• Noted elevated pPMN levels in neutropenic individuals resistant to infection.

Conclusions:

• A distinct, primed PMN population exists and is crucial for effective innate immunity.
• PMN priming is a regulated process influenced by specific growth factors.
• Understanding pPMNs offers insights into immune defense mechanisms, particularly in neutropenic conditions.