CD4 and neoplasm: CD4 T cells are necessary elements for priming tumor-specific CD8 T cells, influencing the differentiation and expansion of tumor antigen-specific CTLs and are essential for generating and maintaining long-term CD8 memory T cell responses (Janssen et al., 2003; Shedlock and Shen, 2003; Sun and Bevan, 2003; Sun et al., 2004).