Thy-1/CD90

Thy-1, the CD90 antigen, was among the first T cell markers described, originally defining thymocyte subsets in mice through the Thy-1.1 and Thy-1.2 allelic variants. The protein is a small GPI-anchored member of the immunoglobulin superfamily with a single V-set domain, resident in lipid rafts. Human Thy-1 marks mesenchymal stromal and stem cells, fibroblasts, endothelial cells and subsets of neurons and hematopoietic cells, which underlies its use in stromal cell isolation. Functional studies implicate Thy-1 in restraint of T cell activation, fibro-fibrotic responses and angiogenesis, and altered expression is reported in hepatic fibrosis and several tumors.