Figure 1.

Monocytes are generated in the bone marrow and mobilized to blood and tissue through cytokine signaling to originate macrophage subsets. In the bone marrow, hematopoietic stem cells give rise to MDCP, which divides into two subsets of monocytes, Ly6C⁺CX3CR1^loCCR2⁺CD62L⁺ and Ly6C^loCX3CR1^hiCCR2⁻CD62L⁻. Both are mobilized to blood through CCR2 and MCP-3 signaling. Once inside the blood vessels, monocytes are able to leave by extravasation and arrive to tissues via CCR2 and CX3CR1 signaling. A macrophage will originate in a tissue-dependent manner and with its own characteristic and name.