CCL2 and neoplasm: The tumor microenvironment promotes the generation of type 2 macrophages, as tumor cells can secrete factors (such as CCL-2) that recruit macrophages to the site of the tumor, and once there the immunosuppressive tumor microenvironment is able to drive these macrophage toward a type 2 phenotype (Bottazzi et al., 1983; Heusinkveld and van der Burg, 2011).