Monoclonal antibody studies of mammalian epithelial keratins: a review.

Significant progress has been made during the past decade with regard to the biochemistry and immunology of keratin filaments. The results indicate that keratin represents a family of more than 17 water-insoluble, cytoskeletal proteins,"2 that keratins are restricted to epithelia and their derivatives;d that different subsets of 210 keratins are expressed in different epithelia,1~2~7-12 that at least two keratin species are required for filament a~sembly,'".'~ and that keratin molecules consist of a central helical domain with two nonhelical end^.^^-^^ Despite these advances, however, it remains a puzzle as to why such a large number of keratin species have evolved to form tonofilaments, while other morphologically similar, intermediate-sized filaments are characterized by a much simpler protein composition with only one to three subunits (for reviews, see Lazaridesl' and other chapters in this volume). To address this fundamental question, we have prepared several monoclonal antikeratin antibodies2' and used them as a tool for studying keratin expression. In this