Nevertheless, we found that CD4+ T cells isolated from the lung tumors of CD4/ALK4-KO mice secreted significantly less IFN-γ and TNF-α concomitantly with increased levels of IL-10 upon ex vivo antigenic re-stimulation compared to CD4+ T cells from WT mice, suggesting that ablation of activin-A signaling specifically in CD4+ T cells restrains the development of effective anti-tumor T cell responses (Fig. 4E). Here, CD4 is linked to neoplasm.