CD90 is a 25-35kD glycosylphosphatidylinositol (GPI)-linked glycoprotein receptor of the immunoglobulin (Ig) superfamily. It is found on murine T-cells, thymocytes, neuronal cells, granulocytic lineage-derived cells, hematopoietic stem cells, fibroblasts, neurons, and Kupffer's cells. CD90 is often used as a marker for a variety of stem cells and mature neuronal axon processes. CD90 appears to play a role in cell-cell and cell-matrix interactions and adhesion during synaptogenesis, nerve regeneration, apoptosis and necrosis, inflammation, fibrosis, and metastasis.