Potential effects of IL-7 on antitumor immune responses.

IL-7, administered systemically or as a local vaccine adjuvant, can potentially enhance immune responses against tumor through a variety of mechanisms. In addition to the expansion and maintenance of T cells expressing TCRs with high affinity for tumor antigens, IL-7 may also recruit low-affinity T cells clones, potentially broadening the immune response. This may have important implications for the control of tumor variants that lose expression of particular antigens. Enhanced generation of mature monocyte-derived dendritic cells by IL-7 combined with other factors, such as GM-CSF, is another mechanism through which IL-7 may enhance an antitumor immune response. Furthermore, IL-7, along with other cytokines, may contribute to the induction of a type 1 immune response and LAK cells. Finally, by diminishing TGF-β production, IL-7 can potentially down-regulate one mechanism through which tumors suppress local immune responses.