The CD9 molecule on stromal cells

Numerous functions have been attributed to CD9 and other members of the tra nsmembrane 4 (TM4) superfamily. CD9 is thought to be involved in cell proli feration, differentiation, motility and survival. It may also function as p art of toxin and virus receptor complexes. Although much remains to be lear ned about molecular mechanisms, the molecule associates with several integr ins, small G proteins, MHC class II molecules and other TM4 superfamily pro teins on a given cell surface membrane. Here, we briefly discuss the CD9 di splayed on stromal cells that support hematopoiesis and the potential impor tance of this molecule to osteoclast differentiation.