CD4 and melanoma: Upon transfer into tumor-bearing lymphodepleted animals, melanoma-reactive tyrp-1-specific TCR transgenic CD4+ T cells (Trp1 cells) produce IFN-γ, TNF-α, and GzmB and acquire potent cytotoxic activity in vitro and in vivo (Quezada et al., 2010, Xie et al., 2010).