Macrophages are essential cellular components of the innate
immune system. They are released from the bone marrow as
immature monocytes and circulate in the blood before extravasating
into tissues, where they differentiate into resident macrophages.
These cells can be found in almost all tissues of the body and,
depending on the local microenvironment, acquire specialized
phenotypic characteristics. Macrophages exhibit diverse functions,
including phagocytosis, antigen presentation, antimicrobial cytotoxicity,
and tissue remodeling as well as the secretion of a wide range
of growth factors, cytokines, complement components, prostaglandins,
and enzymes.1