It is now established that not only the quantity of tumor-infiltrating CD8+ T cells is important, but also their “quality.” Tumor-induced T cell exhaustion has been reported in a number of tumor types, including melanoma (Fourcade et al., 2010) and ovarian cancer (Matsuzaki et al., 2010), and is characterized by expression of co-inhibitory surface receptors, including programmed death receptor 1 (PD-1), lymphocyte-activation gene 3 (LAG-3), and T cell immunoglobulin mucin-3 (Tim-3), either alone or in combination (Fourcade et al., 2010; Sakuishi et al., 2010; Wherry, 2011). Here, HAVCR2 is linked to melanoma.