CD90, also known as Thy1, is an approximately 25-35 kDa glycoprotein that mediates cellular adhesion and exerts wide ranging effects in different tissues (1, 2). Mature mouse CD90 contains one immunoglobulin-like domain followed by a GPI anchor (3-5). CD90 is expressed on hematopoietic progenitor cells, neurons, and activated vascular endothelial cells (6-8). Its species-specific expression in lymphoid cells allows its use as a thymocyte and pan T cell marker in mouse but not in human (1). CD90 can form dimers and higher order multimers (9). It binds to heparin, the proteoglycan Syndecan-4, and Integrins alpha M beta 2, alpha V beta 3, and alpha V beta 5 (8, 10-13). Through these interactions, CD90 inhibits neurite outgrowth (7), promotes astrocyte adhesion (10), mediates the adhesion and extravasation of leukocytes and melanoma cells (8, 12), supports the Thrombospondin-1 induced disassembly of fibroblast focal adhesions (14), and inhibits the activation of latent TGF-beta 1, myofibroblast differentiation, and lung fibrosis (13)
