IMMUNOFLUORESCENCE CHARACTERISTICS AND SOME BIOCHEMICAL PROPERTIES OF LARGE MOLECULAR WEIGHT KERATIN FROM HUMAN PLANTAR STRATUM CORNEUM

Keratin subunits of 64K, 53K, and 43K M.W. from human plantar stratum corneum fibrous proteins were isolated by SDS polyacrylamide gel electrophoresis (PAGE), and the antiserum against each keratin was prepared from rabbits. During indirect immunofluorescence studies of the normal skin, the whole epidermis stained positively with anti‐64K keratin antiserum (64K antiserum), but the positive staining of the basal layer diminished with the dilution of the antiserum. A similar staining pattern was observed with 53K antiserum, although the diminished staining of the basal layer was much less obvious than that with 64K antiserum. In contrast, 43K keratin was distributed throughout the whole epidermis including the basal layer, and no diminished staining with dilution of the antiserum was observed. These results suggest that an immunofluorescence technique using anti‐large M.W. keratin antisera, especially 64K antiserum with a certain degree of dilution, could be used to study the differentiated cells of the epidermis. DEAE‐cellulose column chromatography of keratins revealed that 64K keratin, along with some of the smaller M.W. keratins, was eluted at a low concentration of KCl and could be separated from most of the smaller M.W. keratins, which were eluted at higher concentrations of KCl. In the first process of stratum corneum fibrous protein extraction, 64K protein was observed to be extracted with neutral Tris‐HCl buffer. This protein was found to be immuno‐reactive with the antiserum to 64K keratin which had been extracted with Tris‐HCl buffer containing urea and mercaptoethanol. It is suggested that the biochemical properties of large M.W. keratin are somewhat different from those of smaller M.W. keratins.