CD4 and neoplasm: To address the possibility that IL-25 may also affect Th2 response inside primary breast tumors, we analyzed tumor-infiltrating IL-4-, IL-5- and IL-13-secreting CD4+ T cells in primary adenocarcinomas of MMTV-PyMT mice, and found that IL-25 blocking antibody significantly decreased the numbers of IL-4-secreting CD4+ cells while had no effect on IL-5 and IL-13 expression (Fig. 4A).