PDCD1LG2 and viral infectious disease: We previously showed that viral infection or stimulation with a synthetic dsRNA analog, polyinosinic-polycytidylic acid (poly I:C), increased PD-L1 and PD-L2 expression on human bronchial epithelial cells, and the NF-κB pathway plays an essential role in poly I:C–induced upregulation of PD-L1 (12–14).