Figure 1.

Blood monocyte and wound macrophage phenotypes in the mouse. Macrophages in wounds originate mainly from circulating monocytes. The figure depicts the two subpopulations of murine blood monocytes that are distinguished by their expression of Ly-6C and chemokine receptors CCR2 and CX3CR1. Ly-6C^highCCR2^high monocytes are recruited into wounds early after injury and are known to produce proinflammatory cytokines and to clear wound debris by phagocytosis. Ly-6C^lowCX3CR1^high monocytes subsequently infiltrate wounds and express TGF-β and VEGF. There is conflicting evidence in the literature as to whether Ly-6C^highCCR2^high cells can become Ly-6C^lowCX3CR1^high in the wound. Functions specifically associated with early or late wound macrophages are linked by a black arrow. Other wound macrophage functions not yet clearly assigned to either macrophage population are indicated with a gray arrow. MHCII, major histocompatibility complex type 2; MR, mannose receptor-1; PMN, polymorphonuclear leukocytes.