Opening a Niche for Therapy: Local Lymphodepletion Helps the Immune System to Fight Melanoma

In this issue, Fujiwara et al. report that local ablation of CD4+ T cells in a murine B16 melanoma model, together with concomitant activation of the immune system by OX40L, leads to complete rejection of the melanomas. Rejection was driven mainly by CD8+ T cells, which infiltrated the melanomas and secreted sizeable amounts of IFN-γ. However, CD8+ T-cell infiltration also caused the recruitment of immunosuppressive myeloid-derived suppressor cells (MDSCs). Although these cells did not prevent the rejection of the melanomas, in clinical settings the long-term repopulation of tumors by MDSCs may counteract successful treatment. Thus, local ablation of CD4+ leukocytes may improve anti-melanom…