Textoris-Taube and colleagues demonstrate that ERAP1, but not ERAP2, is involved in the generation of the glycoprotein 100 (gp100)209-217 immunogenic epitope derived from melanoma differentiation antigen (gp100)PMEL17, and promotes the activation of gp100209-217-specific CD8+ T cells by melanoma cells (Table 1) (70). The gene discussed is ERAP1; the disease is melanoma.