CD274 and Autoimmunity: The pivotal role of PD-1 in maintaining peripheral tolerance40 places patients receiving systemic blockade at risk of autoimmunity.7, 41 Strong expression of PD-1/PD-L1 within the tumor microenvironment may predict a favorable response to PD-1 blockade41, 42 but conversely increases the risk of unleashing local collateral tissue damage.