Concerning human melanomas, it is known that long-term survival correlates with low levels of monomeric IL-15 in the serum, whereas a poor survival outcome correlates with high levels of monomeric IL-15, possibly reflecting the increased expressions of T cell immunoglobulin and mucin-domain containing-3 (TIM-3) and programmed cell death protein 1 (PD-1) in both NK and T cells (20). This evidence concerns the gene PDCD1 and melanoma.