Macrophage colony-stimulating factor (M-CSF), total c-Fms, and phospho-c-Fms are upregulated in human rheumatoid arthritis (RA) synovium. (a) Levels of M-CSF in synovial fluid from patients with RA (n = 14), osteoarthritis (OA) (n = 15), or psoriatic arthritis (PsA) (n = 12) were measured by Luminex bead-based arrays. Values are the mean ± standard error of the mean. **P < 0.01 compared with RA samples. (b) Representative immunohistochemical images of RA synovium stained with antibodies against c-Fms, phospho-c-Fms, or isotype controls.