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By use of a mouse hybridoma technique, monoclonal antibodies were produced against hair fibrous proteins, which were extracted from normal human hairs. Three monoclonal antibodies, designated as HKN-2, HKN-4, and HKN-6, were chosen and used to investigate the immunological characteristics of hair fibrous proteins. Epidermal fibrous proteins were also extracted from human sole callus horny materials. Hair or epidermal fibrous proteins were electrophoretically separated on polyacrylamide gels with sodium dodecyl sulfate. By immunoblot analyses, HKN-2 and HKN-4 marked the electrophoretic bands of both proteins; however, HKN-6 reacted only with the bands of hair fibrous proteins. Immunohistochemically, all three monoclonal antibodies stained the keratogenous zone of anagen hairs. HKN-6 did not react with any other skin components or with tissues of other organs examined. Although HKN-2 showed reactions with skin epithelial tissues, except for epidermal basal cells and secretory cells of sweat glands, the reactivity of HKN-2 was limited within the skin. HKN-4 displayed a broad crossreactivity with all of the skin epithelial cells and various epithelial cells of other organs. These findings indicate that some components of hair fibrous proteins are immunologically specific to hair cells, whereas others broadly crossreacted with the fibrous proteins of other skin epithelial cells or with those of various epithelial cells. The anti-hair keratin monoclonal antibodies seem useful to examine the differentiation patterns of epithelial cells and tissues.

Skin lesions of three patients with inflammatory linear verrucose epidermal naevus (ILVEN) were examined. Histologically, orthokeratosis and parakeratosis were alternately seen in the acanthotic epidermis. By N-(7-dimethylamino-4-methyl-3-coumarinyl)maleimide staining, the horny cells in the parakeratotic epidermis showed a cytoplasmic SH pattern and a weak membranous SS pattern. The orthokeratotic epidermis revealed an increased involucrin expression, whereas the parakeratotic epidermis showed almost no involucrin expression. Ultrastructurally, in the parakeratotic epidermis, the living keratinocytes had prominent Golgi apparatuses and vesicles in the cytoplasm. In the intercellular spaces in the upper spinous layer through to the lower horny layer, an electron dense, homogeneous substance was deposited. The cytoplasm of the horny cells was filled with keratin filaments and contained remnants of nucleus and cytoplasmic membrane structures, and some lipid droplets. The marginal band formation was incomplete. Most of these ultrastructural abnormalities were not found in the orthokeratotic epidermis. There are both similarities and differences in histopathogenesis of the parakeratotic epidermis between ILVEN and psoriasis. A unique finding was the lack of involucrin expression in the ILVEN parakeratotic epidermis.

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A skin biopsy specimen was obtained from a 1-month-old female with epidermolysis bullosa simplex (Koebner). Histologically, an intraepidermal separation was seen and considered to be formed by cytolysis of the epidermal basal cells. Ultrastructurally, the basal cells were lacking in cytoplasmic tonofilaments, and the initial change of the cytolysis seemed to be cleavages of the cytoplasm. Immunohistochemically, a basal cell keratin was expressed in a suprabasal cell layer but not in the basal cell layer, and a panepithelial keratin was not detected in the basal cell layer. These findings suggest that keratin production of the epidermal cells may be delayed, resulting in a weakness of the basal cells against minor trauma to the skin.