Claudin-5 (E5D9Y) Rabbit mAb recognizes endogenous levels of total claudin-5 protein. Species reactivity for immunohistochemistry is human only. Non-specific staining was observed in skeletal muscle by immunohistochemistry.

Monoclonal antibody is produced by immunizing animals with a synthetic peptide corresponding to residues surrounding Ala202 of human claudin-5 protein.

Tight junctions, or zonula occludens, form a continuous barrier to fluids across the epithelium and endothelium. They function in regulation of paracellular permeability and in the maintenance of cell polarity, blocking the movement of transmembrane proteins between the apical and the basolateral cell surfaces. Tight junctions are composed of claudin and occludin proteins, which join the junctions to the cytoskeleton (1,2). The claudin family is composed of 23 integral membrane proteins, and their expression, which varies among tissue types, may determine both the strength and properties of the epithelial barrier. Alteration in claudin protein expression pattern is associated with several types of cancer (2,3). 

Claudin-5, highly expressed in brain and lung tissue, is a primary component of the tight junctions of blood-brain barrier endothelial cells. The blood-brain barrier regulates homeostatic and pathological conditions in the brain by limiting passage of material circulating to the brain. The blood-brain barrier can also impede the effectiveness of small molecule therapeutics (4). Claudin-5 is also thought to regulate tumor cell motility brain metastasis (5).