Citation

The paired immunoglobulin-like type 2 receptor (PILR) family consists of two functionally opposite members, inhibitory PILR and activating PILR receptors. PILRs are widely expressed in various immune cells and interact with their ligands, especially CD99 expressed on activated T cells, to participate in immune responses. Here we investigated whether PILR-derived agonists inhibit 1 integrin activity as ligands for CD99. PILR-derived peptides as well as PILR-Fc fusion proteins prevented cell adhesion to fibronectin through the regulation of 1 integrin activity. Especially, PILRpep3, a representative 3-mer peptide covering the conserved motifs of the PILR extracellular domain, prevented the clustering and activation of 1 integrin by dephosphorylating FAK and vinculin, which are major components of focal adhesion. In addition, PILRpep3 inhibited transendothelial migration of monocytes as well as endothelial cell tube formation. Furthermore, upon intraperitoneal injection of PILRpep3 into mice with collagen-induced arthritis, the inflammatory response of rheumatoid arthritis was strongly suppressed. Taken together, these results suggest that PILR-derived agonist ligands may prevent the inflammatory reactions of rheumatoid arthritis by activating CD99.