CCL18 and immunoglobulin G4-related sclerosing disease: Previous studies have shown that CD163+ M2 macrophages are activated by TLR7, accumulated in multiple organs of patients with IgG4-RD, thus promoting fibrotic phenotype by producing CCL18 and IL-10 or activating T helper type 2 (Th2) immune response via IL-33 (32–34).