CD4 and neoplasm: We found that tumor-induced senescent CD4+ T cells strongly inhibited the proliferation of responding CD4+ T cells (Fig 1F), which is consistent with the findings from our and other groups that senescent CD8+ T cells have negative regulatory functions on immune responses induced by vaccination and transplantation (Chen et al, 2009; Cortesini et al, 2001; Ye et al, 2012).