Monocytes and macrophages: developmental pathways and tissue homeostasis

Area of Science:

• Immunology
• Cell Biology
• Developmental Biology

Background:

• Monocytes and macrophages play vital roles in immunity and tissue homeostasis.
• Dysregulation of these cells contributes to various pathologies, making them therapeutic targets.
• Understanding their origin and maintenance is crucial for developing interventions.

Purpose of the Study:

• To review recent evidence on monocyte and macrophage development.
• To elucidate the origins and homeostasis mechanisms of tissue macrophages.
• To highlight the shift in understanding from monocyte-derived to embryonic-derived macrophages.

Main Methods:

• Review of existing scientific literature and studies.
• Analysis of experimental data on immune cell populations.
• Synthesis of findings on macrophage origins and self-renewal.

Main Results:

• Monocytes contribute minimally to most tissue macrophage populations in steady-state and during inflammation.
• The majority of tissue macrophages are derived from embryonic precursors.
• These embryonic-derived macrophages are established early and self-renew throughout adulthood.

Conclusions:

• The prevailing view of monocyte-derived macrophages is being revised.
• Embryonic precursors are the primary source of most tissue macrophage populations.
• This paradigm shift has significant implications for understanding immune cell maintenance and therapeutic strategies.