IL4 and neoplasm: Interestingly, high levels of Th2 cell-derived cytokines were reported in the sera of different types of human breast cancer patients, and the levels of IL-4 and the number of tumor-infiltrating CD4+ T cells were found to positively correlate with tumor progression and metastasis to sentinel lymph nodes (Pedroza-Gonzalez et al., 2011; Kohrt et al., 2005; Mantovani et al., 2008), highlighting the clinical relevance of type 2 immune cells in the pathogenesis of human breast tumors.