Rabbit Anti-Human IVL polyclonal antibody for IHC-P. Involucrin is a soluble cytoplasmic protein precursor of the epidermal cornfied envelope that becomes cross-linked by transglutaminase during envelope assembly. Involucrin is expressed in a range of stratified squamous epithelia, including the cornea which lacks a distinct cornfied layer. The protein is a useful marker of terminal differentiation. It is tightly linked to the onset of differentiation and first expressed in the immediate suprabasal layers of the epidermis.