CCL18 and breast cancer: To determine whether CCL18+ TAMs could recruit naive T cells to tumors, we used a tumor slice assay in which freshly resected breast cancer slices were overlaid with autologous naive CD4+ T cells labeled with carboxyfluorescein succinimidyl ester (CFSE), and the number of stained CD4+ T cells bound was counted and compared to the numbers of CCL18+ TAMs in the tumor23.