Importantly, we do note that previous work on T cell reactivity against established B16 melanoma has documented incomplete differentiation in CD8+ T cells responding not only to the model neoantigen SIINFEKL but also to an endogenously processed Ag derived from the melanocyte differentiation protein tyrosinase (Tyr369) [14], a well‐characterized and naturally occurring human tumor Ag. Here, PROS1 is linked to melanoma.