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![A review of mechanisms of resistance to immune checkpoint inhibitors and potential strategies for therapy](https://image.oaes.cc/9e4a97d6-0e6f-45c7-8665-427cfc0139bc/3496.fig.1.jpg)
Figure 1. Steps involved in the generation of an effective tumor-directed T cell response through the formation of tumor reactive T cells, the activation of effector T cell function and the formation of effector memory T cells (A); resistance to immune checkpoint inhibitors may occur due to multiple different factors within the tumor cell or the tumor microenvironment (B). MHC: major histocompatibility complex; PD-1: programmed death 1; PD-L1: programmed cell death ligand 1; MDSC: myeloid-derived suppressor cell; IDO: Indoleamine 2,3-dioxygenase; APC: antigen-presenting cell