PDCD1 and neoplasm: To conduct the computational experiment, the following conditions were taken into consideration: (i) the absence of distant tumor Ag in the lung, leading to the shutting down of the TCR signal (U = 0 in the Equations (SI-2.1a–d), (ii) the abundance of inflammatory cytokines, including TNFα and IFNγ, known to induce the expression of both PD-1 and PD-L1 (SI-1), and (iii) the abundance of IL-2, which induces Blimp-1 (SI-1).