Cayman TAPA-1/CD81 Extracellular Domain (human, recombinant; His-tagged)

CD81, also known as target of antiproliferative antibody 1 (TAPA-1), is a member of the tetraspanin protein family with roles in B cell biology and T cell activation and as a virus host factor.^1,2 It is composed of four transmembrane segments, which are packed as two pairs of helices, and an extracellular loop at the outer membrane leaflet that, unlike other tetraspanin proteins, is non-glycosylated and subject to post-translational acylation.^2,3 On the surface of B cells, CD81 associates with CD19 and CD21 to facilitate adhesion and reduce the threshold for B cell receptor activation, as well as with MHC class II molecules as a component of the B cell surface receptor complex.^3,4,5 On T cells, CD81 interacts with CD4 and CD8 and functions as a co-stimulator of naïve T cell activation in conjunction with CD3 and CD28.^1,6 CD81 also acts as a virus host factor, and neutralization of CD81 with anti-CD81 antibodies reduces HIV-1 replication and inhibits influenza A virus uncoating and viral budding, as well as inhibits coronavirus (CoV) and hepatitis C virus (HCV) cell entry.⁷ CD81 levels are increased in several lymphoma cell lines, and antibody-driven neutralization of CD81 induces complement-dependent cytotoxicity, antibody-dependent cellular phagocytosis, and cytotoxicity in these cells.⁵ Cayman’s TAPA-1/CD81 Extracellular Domain (human, recombinant; His-tagged) protein consists of 108 amino acids and has a calculated molecular weight of 12.1 kDa.

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