P-selectin glycoprotein ligand-1 (PSGL-1) has long been studied as an adhesion molecule involved in immune cell trafficking and is recognized as a regulator of many facets of immune responses by myeloid cells. PSGL-1 also regulates T cell migration during homeostasis and inflammatory settings. However, recent findings indicate that PSGL-1 can also negatively regulate T cell function. Because T cell differentiation is finely tuned by multiple positive and negative regulatory signals that appropriately scale the magnitude of the immune response, PSGL-1 has emerged as an important checkpoint during this process. We summarize what is known regarding PSGL-1 structure and function and highlight how it may act as an immune checkpoint inhibitor in T cells.

Author Info: (1) Infectious and Inflammatory Disease Center and National Cancer Institute (NCI)-Designated Cancer Center, Sanford Burnham Prebys Medical Discovery Research Institute, La Jolla,

Author Info: (1) Infectious and Inflammatory Disease Center and National Cancer Institute (NCI)-Designated Cancer Center, Sanford Burnham Prebys Medical Discovery Research Institute, La Jolla, CA 92037, USA; Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA. (2) Infectious and Inflammatory Disease Center and National Cancer Institute (NCI)-Designated Cancer Center, Sanford Burnham Prebys Medical Discovery Research Institute, La Jolla, CA 92037, USA. (3) Infectious and Inflammatory Disease Center and National Cancer Institute (NCI)-Designated Cancer Center, Sanford Burnham Prebys Medical Discovery Research Institute, La Jolla, CA 92037, USA. (4) Infectious and Inflammatory Disease Center and National Cancer Institute (NCI)-Designated Cancer Center, Sanford Burnham Prebys Medical Discovery Research Institute, La Jolla, CA 92037, USA. Electronic address: lbradley@sbpdiscovery.org.