Specificity: Recognizes the human ~22kD Claudin 4 protein and does not cross-react with the protein at 55kD. Species cross-reactivity: rat ileum homogenates and canine MDCK cell lysates by Western Blot and Immunofluorescence. Reactivity has also been confirmed with formalin-fixed, paraffin-embedded (FFPE) human normal colon and colon cancer tissues by Immunohistochemistry.