Alternatively activated macrophages derived from monocytes and tissue macrophages are phenotypically and functionally...

Area of Science:

• Immunology
• Cell Biology

Background:

• Macrophages can adopt an alternatively activated phenotype (AAMs) upon stimulation with interleukin-4receptor(R)α.
• AAMs can arise from tissue-resident macrophages or recruited inflammatory monocytes, but their distinct origins' impact on phenotype and function remains unclear.

Purpose of the Study:

• To investigate whether AAMs derived from different sources (monocytes vs. tissue-resident macrophages) exhibit distinct phenotypes and functions.
• To identify specific molecular markers and functional properties differentiating these AAM subsets.

Main Methods:

• Transcriptional profiling analysis.
• Flow cytometry for marker expression (CX3CR1-GFP, CD206).
• Assessment of aldehyde dehydrogenase activity and retinoic acid production.
• Analysis of T cell differentiation (FoxP3(+) cells).

Main Results:

• Both monocyte-derived and tissue-derived AAMs expressed Arg1, Chi3l3, and Retnla.
• Monocyte-derived AAMs uniquely upregulated Raldh2 and PD-L2, showed high CX3CR1-GFP and CD206 expression, and possessed high aldehyde dehydrogenase activity.
• Monocyte-derived AAMs promoted retinoic acid production and FoxP3(+) cell differentiation, while tissue-derived AAMs expressed high uncoupling protein 1.

Conclusions:

• AAMs derived from inflammatory monocytes and tissue-resident macrophages are phenotypically and functionally distinct.
• Monocyte-derived AAMs possess immune-regulatory properties linked to retinoic acid production.
• Tissue-derived AAMs exhibit characteristics distinct from immune regulation, suggesting lineage-dependent AAM functions.