FIGURE 1.

The origin and marks of RA‐related macrophages in mice. Peritoneal macrophages, bone marrow‐derived macrophages, peripheral blood monocytes and synovial macrophages are widely studied in RA and animal arthritis model. These heterogeneous macrophages show different marks, roles and origins. Bone marrow‐derived macrophages are derived from Ly6c^hi monocytes, which can possess the phenotype of resident macrophages. Two main macrophage subsets found in peritoneal cavity of adult mice named as LPM and SPM. Approximately 90% peritoneal macrophage are LPMs which are derived from foetal liver macrophages, SPMs are derived from bone marrow‐derived monocytes. Two types of SM were found: embryonic SMs (ESMs) which were F4/80⁺CD11b^‐ and appeared at a mid‐embryonic stage; and bone marrow‐derived SMs (BMSMs), which were F4/80^‐CD11b⁺ and appeared at a late‐embryonic stage. ESMs expressed anti‐inflammatory cytokines such as IL‐4 and IL‐10, and BMSMs expressed pro‐inflammatory cytokines such as IL‐1β and TNF