CCL18 and immunoglobulin G4-related sclerosing disease: The M2 macrophages were found to secrete IL-33 in patients with IgG4-RD [27, 28], as well as profibrotic factors such as interleukin-10 (IL-10), interleukin-13 (IL-13), and C-C Motif Chemokine Ligand 18 (CCL18) [26].