Figure 1
Development and differentiation of macrophages. Bone marrow-derived monocytes enter peripheral blood and circulate for several
days in an inert state before entering tissues and differentiating into tissue resident macrophages. Tissue resident macrophages
include histiocytes (connective tissue), microglial cells (nervous system), Kupffer cells (liver) and osteoclasts (bone).
Macrophages are recruited to tissues to restore resident populations or respond to diverse inflammatory and immune stimuli.
The acquired phenotype of recruited macrophages reflects signals from the microenvironment in which they reside. These macrophages
are broadly classified as classically or alternatively activated macrophages. M-CSF, macrophage colony stimulating factor;
GM-CSF, granulocyte-macrophage colony stimulating factor.