CD44 is a transmembrane glycoprotein and also major hyaluronan receptor, mediating cell responses to the extracellular microenvironment. In 1980s, it was first described as a surface molecule restricted to few immune cells like lymphocytes, thymocytes, and granulocytes (Dalchau et al. 1980), but later it was recognized as a novel human erythrocyte cell surface antigen, lymphocyte homing receptor, and leukocyte surface glycoprotein (Stefanová et al. 1989). Today, CD44 is being described as an adhesion molecule expressed in various cell types which includes both epithelial cells (even in keratinocytes) and connective tissue cells (endothelial cells, fibroblasts and leukocytes). It participates in a...