+Cd9 is a transmembrane [protein](/wiki/protein) found on the surface of many [cells](/wiki/cell). As a member of the tetraspanin family, it plays a critical role in cell adhesion, migration, and signaling pathways. Its presence influences various biological processes, from immune responses to fertilization.
+## See also
+- [Tetraspanin](/wiki/tetraspanin)
+- [Cell Adhesion](/wiki/cell_adhesion)
+- [Immune System](/wiki/immune_system)
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