In inflamed GCA vessels, M-CSF expression was found to be highly localized in the area with CD206+/MMP-9+/YKL-40+ macrophages, suggesting that M-CSF produced by CD206+/MMP-9+/YKL-40+ macrophages primes adjacent macrophages to express FRβ. The gene discussed is CHI3L1; the disease is temporal arteritis.