Production and characterization of monoclonal antibodies reactive with subsets of epidermal cells

Monoclonal antibodies were raised against an extract of human callus to provide markers of cell differentiation. Three antibodies, LMM1, LMM2 and LMM3, have been isolated and react with different histological structures in skin. LMM1 reacts with two distinct proteins of 62-65 kD molecular weight and stains cells in the stratum spinosum and stratum granulosum of normal epidermis. This antibody stains a high proportion of cultured epidermal cells showing a diffuse cytoplasmic reactivity with nucleolar staining also being present in some cells. LMM2 reacts with several lower molecular weight proteins, the two major bands being 38 kD and 44 kD. It stains basal epidermal cells strongly and stratum spinosum cells less strongly. A population of cultured keratinocytes reacts with an intense fibre stain suggesting that this antibody is directed against an intermediate filament or intermediate filament-associated protein. LMM3 reacts with a 48 kD protein. Although it does not stain cells in normal epidermis its staining of a subpopulation of hair follicle cells is consistent with this protein being a cytokeratin. It also stains a population of cultured keratinocytes, the main reactivity being against mitotic cells. The anti-cytokeratin or anti-cytokeratin-associated reactivity of these three antibodies is supported by their altered reactivities against psoriasis epidermis, where modifications of cytokeratin biosynthesis are known to occur.