IL7 and neoplasm: This observation is supported by the finding that IL-7 was preferable for ex vivo expansion of tumor-specific murine CD4+ Th cells compared with IL-2.32 IL-15 has been shown to synergize with IL-7 to regulate homeostatic proliferation of memory CD8+ T cells but are not required for the proliferation of memory CD4+ Th cells.33 Similarly, we observed that IL-7 and IL-15 did not synergize to enhance expansion of either naive or antigen-specific CD4+ Th cells.