Neutrophilic asthma features increased airway classical monocytes

Area of Science:

• Immunology
• Respiratory Medicine
• Cell Biology

Background:

• Monocytes and macrophages are key innate immune cells in airways.
• Their distinct roles and regulation in asthma remain poorly understood.
• Clinical studies often fail to differentiate between these cell types.

Purpose of the Study:

• To differentiate and quantify macrophages, monocytes, and monocyte subsets in sputum and blood.
• To examine the relationship between these cells and asthma's inflammatory and clinical features.
• To investigate monocyte subset distribution in relation to airway inflammation and asthma severity.

Main Methods:

• Flow cytometry was used to identify and quantify macrophages, monocytes, and subsets (classical, intermediate, non-classical) in sputum and blood.
• CD206, a marker of monocyte tissue differentiation, was measured in sputum.
• Relationships were assessed with airway inflammatory phenotypes (neutrophilic, eosinophilic, paucigranulocytic) and asthma severity.

Main Results:

• Sputum macrophage numbers were reduced, while classical monocyte proportions increased in asthma patients compared to non-asthma controls.
• Neutrophilic asthma showed higher sputum classical and CD206- monocyte numbers compared to paucigranulocytic and eosinophilic asthma, respectively.
• Severe asthma exhibited increased blood classical monocyte proportions and numbers compared to non-severe asthma.

Conclusions:

• Flow cytometry effectively distinguishes sputum macrophages, monocytes, and subsets, revealing compartment-specific monocyte dysregulation in asthma.
• Increased classical and CD206- monocytes in neutrophilic asthma suggest co-recruitment of monocytes and neutrophils.
• Further research is warranted to understand how airway monocyte dysregulation influences asthma activity.