CX3CR1 and immunoglobulin G4-related sclerosing disease: In contrast, the levels of CX3CL1 (ligand for CX3CR1) and CCL5 (a ligand for CCR1) were upregulated in IgG4-RD tissues, indicating elevated chemokines in tissues could be important factors for the migration of different MN subsets (Figure 5E).