PSGL-1

Class

Immune checkpoint enhancer

PSGL-1 (P-selectin glycoprotein ligand-1) is a cell-surface glycoprotein expressed mainly on leukocytes, the white blood cells that mediate immune responses. Its best-characterized role is guiding leukocytes to sites of inflammation by binding selectin molecules on blood vessel walls, allowing cells to roll along and then exit into inflamed tissue. More recently, PSGL-1 has been recognized as a ligand for an inhibitory receptor on T cells, meaning it can deliver a braking signal that dampens T-cell activation. Because of this dual biology, PSGL-1 can be approached from two opposite directions: blocking it to intensify immune attack, or enhancing its inhibitory signaling to restrain an overactive immune system. An 'immune checkpoint enhancer' aimed at PSGL-1 pursues the latter strategy, seeking to reinforce the natural brake on T-cell responses. This approach is relevant to autoimmune and chronic inflammatory conditions, where T cells are excessively or inappropriately activated against the body's own tissues, in contrast to cancer immunotherapy, which typically removes such brakes rather than strengthening them.