CCL18 and neoplasm: A number of different immuno-mediators, such as programmed death-ligand 1 (PD-L1), macrophage colony stimulation factor (M-CSF), C-C motif chemokine ligand 2 (CCL2), C-C motif chemokine ligand 17 (CCL17), C-C motif chemokine ligand 18 (CCL18) and C-C motif chemokine ligand 22 (CCL22), predominantly released by M2 macrophages, have been linked to increased numbers of both macrophages and Tregs in tumor tissue (15, 17, –, 19).