Subcellular distribution of 220 kDa antigen in the intercellular spaces of normal human epidermis

We generated a monoclonal antibody, 7C1, to an extract of pig snout skin used as antigen. The antigen for 7C1 was identified by immunoblotting as a 220 kDa epidermal protein. It was found immunologically to be distributed mainly in the intercellular spaces throughout the living cell layers of normal human epidermis, but its distribution changed in some keratinizing disorders. Study of the association of this protein with subcellular structures by immunoelectron microscopy of normal human skin revealed that it was localized in (1) lamellar granules, (2) intercellular spaces, especially in the lamellar structures derived from the lamellar granules, (3) small vesicles near the cell boundaries and (4) small vesicles in the Golgi apparatus. These results suggest that in humans the 220 kDa protein originates in the Golgi apparatus and is secreted via either the lamellar granules or the small secretory vesicles into the intercellular spaces of the epidermis, where it may be involved in the epidermal permeability barrier function and possibly in keratinizing differentiation.