Fig. 1

A schematic representation of the model for the main interactions between the melanoma cancer, the cellular immune system, and the immune checkpoint blocker pembrolizumab. The model is based on the following assumptions: tumor cells stimulate antigen-presenting cells, APCs, depending on the tumor immunogenicity; functional APCs activate effector CD8+ T cells, which may eliminate tumor cells; tumor infiltrating lymphocytes, TILs, become exhausted, independently of the tumor cells elimination; tumor growth is determined by its net growth rate and by the rate of its destruction by Effector TILs; immunotherapy extends the activation of effector TILs, and reduces their exhaustion. Annotated ellipses represent the dynamic variables of the model, while arrows represent the interaction between them (see legends in the box)