IL13 and neoplasm: In addition, chemical mediators produced by tumor cells and/or immune cells such as IL-1, IL-4, IL-6, IL-10, IL-13, and prostaglandin (PG) E2 can directly suppress the cytotoxic action of macrophages, inhibiting both their migration toward the chemotactic stimuli and their adherence to endothelial cells, or indirectly by modulating the immune response by stimulating macrophages to produce PGE2 [3].