Balancing Act: PD-1, PD-L1, and the Inflammatory Tightrope of Acute Respiratory Distress Syndrome
PD-1 (programmed cell death protein 1) and its cognate ligands (PD-L1 and PD-L2) are cell surface proteins that act as “checkpoints” of the adaptive immune system and promote tolerance to self-antigen. PD-L1 expressed by antigen-presenting cells binds PD-1 receptor on T cells inhibiting proliferation, production of cytokines, and other antigen-specific responses. Soluble forms of the proteins generated by splice variants or proteinase cleavage likely function similarly to cell-bound forms. The proteins
