Figure 1.

Evaluation of mathematical models which describe tumor vs. immune system interactions. “One-ODE” approach, simplistic description of tumor growth kinetics; “Two-ODE” approach, a typical “Predator-Prey” model, incorporating a basic description of tumor vs. immune system interactions; “Three-ODE” approach, incorporating additional immuno-modulating factor(s); “Four-ODE” approach, including considerations for immuno-suppression; mechanistic multi-compartmental model, taking into account essential biological principles underlying the IO cycle concept (21); TV, tumor volume; CTL, cytotoxic T lymphocytes; IMF, immuno-modulating factor; ISF, immuno-suppressive factor; mDC, level of mature dendritic cells; _nT_eff, non-differentiated T effectors cells; _dT_eff, differentiated T effectors cells; Treg, regulatory T cells; PD-L1, level of PD-L1 expression; Ag_sys, level of systemic antigen; IAR, immuno-activation rate function; green line, positive regulation, red line negative, regulation; back line, variable turnover.