Proteins of the cornified envelope.

The cornified envelope of keratinocytes is an insoluble structure formed beneath the plasma membrane at the base of the stratum corneum. It is made by cross-linking precursor proteins by a membrane-associated transglutaminase. Using the cornified envelope of cultured human keratinocytes as the immunogen, we obtained a number of monoclonal antibodies which stained epidermis in a variety of ways. The peripheral staining pattern has been associated with several envelope precursors and this has been confirmed by western blots. A mouse IgM monoclonal antibody directed against epidermal basal cell hemidesmosomes was also discovered. By immunofluorescence, the monoclonal antibody produced a strong linear staining of the basement membrane zone and a polar cap on trypsin-dissociated epidermal basal cells. By immunoelectron microscopy, immunoreactants were present in the attachment plaques of hemidesmosomes on guinea pig esophagus. However, no protein reactive with the antibody was detected. This study suggests that an antigen associated with the basal cell hemidesmosomes may be incorporated in the cornified envelope.