FIGURE 1.

A possible mechanism for acquired resistance to PD-1 inhibition. Anagnostou and colleagues⁷⁶ discovered that acquired resistance to blockade of the PD-1/PD-L1 axis can potentially be explained by a shifting mutational landscape, which might cause the loss of neoantigens. That loss abrogates the ability of T cells in the tumour microenvironment to recognize the malignant cells as foreign, which renders therapy with PD-1 axis blockade ineffective. CD8+ T cells, regulatory T cells (T regs) and myeloid-derived suppressor cells (MDSCs) are all pictured here as part of the tumour microenvironment. ICI = immune checkpoint inhibitor; TCR = T cell receptor; MHC = major histocompatibility complex.