The tetraspanin CD81, also known as TAPA-1, was originally identified as the target protein for an antibody that inhibited lymphocyte proliferation. More recently it was identified as a receptor defining hepatitis C virus (HCV) infection of hepatocytes. CD81 is expressed on T and B cells, NK cells, monocytes, dendritic cells, thymocytes, endothelial cells, and fibroblasts. CD81 induces B cell adhesion via VLA-4 integrin and has been shown to play a role in early T cell development. Antibody engagement of CD81 on immune cells promotes actin cytoskeletal rearrangement and altered cellular function including: T cell stimulation via activation of Lck, a Src family protein kinase; inhibition of NK cytolytic activity, and B cell activation and proliferation.
Anti-Human CD81 (5A6)-145Nd—100 Tests