CD44 is a type I transmembrane glycoprotein that mediates cell-cell and cell-matrix interactions through its affinity for hyaluronic acid (HA) and possibly also through its affinity for other ligands. Adhesion with HA plays an important role in cell migration,tumor growth and progression. CD44 is also involved in lymphocyte activation,recirculation and homing,and in hematopoiesis. This protein exists in multiple isoforms (with molecular weight ranging from 16 kDa to over 200 kDa) generated by alternative RNA splicing and undergoes extensive post-translational modifications.