Fig. 1From: Abscopal effect of radiotherapy combined with immune checkpoint inhibitorsMechanism of the abscopal effect. Radiotherapy (RT) can lead to immunogenic cell death and the release of tumor antigens by irradiated tumor cells. These neoantigens are taken up by antigen-presenting cells (APCs), such as dendritic cells (DCs) and phagocytic cells. The APCs interact with tumor antigens and then migrate to the lymph nodes where they present antigens to T cells, a process that is mediated by the MHC pathway and other co-stimulatory signals, such as CD80 and CD28. After activation by multiple signals, T cells, especially the CD8+ T cells, are activated and begin to propagate. As a result, activated effector T cells exit the lymph nodes and home to tumors, including primary tumors and non-irradiated tumor metastases, to exert their effect of killing tumor cells. However, cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) competitively combines with CD80/86 and inhibits the activation of T cells. Following T cell activation, programmed cell death 1 (PD-1) receptors that are expressed on the T cell surface bind primarily to programmed death-ligand 1 (PD-L1) and inhibit immune responses. The administration of immune checkpoint blockades of CTLA-1, PD-1, and PD-L1 can enhance the anti-tumor immunity of RTBack to article page