In addition, CD4+ T cells that reside in tumors display Th2 immunity phenotype which has been shown to contribute to tumor growth and poor prognosis in breast cancer as well as in other cancers.8 Th2 cells in tumors secrete anti-inflammatory cytokines such as interleukin (IL)-4, IL-13, and IL-10, which inhibit Th1 antitumorigenic immunity and CD8+ cytotoxic T cell activity. Here, IL4 is linked to breast cancer.