CD4 and neoplasm: Hung et al. (1998) have reported that activated CD4+ T cells may induce delayed type hypersensitivity and attract inflammatory cells, such as macrophages, neutrophils, eosinophils, and NK cells to tumor cells. Tumor infiltrating macrophages will be lost with the deletion of CD4T cells, and the tumor cannot be protected. This suggests that CD4+ T cells could directly activate macrophages in lymph nodes or tumor tissues.