Keratins are a group of water-insoluble proteins that form monofilaments, a class of intermediate filament. These filaments form part of the cytoskeletal complex in epidermis and in most other epithelial tissues. Nineteen human epithelial keratins are resolved with two-dimensional gels electrophoresis (1). These can be divided into acid (pI <5.7) and basic (pI >6.0) subfamilies. The acidic keratins have molecular weights of 56.5, 55, 51, 50, 50’, 48, 46, 45 and 40 kD. The basic keratins have molecular weights of 65-67, 64, 59, 58, 56 and 52kD. Members of the acidic and basic subfamilies are found together in pairs. The composition of keratin pairs varies with the epithelial cell type, stage of differentiation, cellular growth environment, and disease state (2-4). The 56.5/65-67kD pair is present in keratinized (differentiated) epidermis. The 55/64kD pair is characteristic of normal (corneal-type) epithelial differentiation (1,2). The 51/59kD pair is characteristic of the stratified squamous epithelial of internal organism such as esophagus and tongue (1,3). The 51/58kD pair is a keratinocyte marker; this pair is present in almost all stratified epithelia irrespective of the state of cellular stratification (1,2). The 48/56kD pair is characteristic of hyperproliferative (de-differentiated) keratinocytes (1,5). The 45/52kD pair and to a lesser extent, the 46/54kD pair are characteristic of simple epithelia (1). The 40kD keratin is present in most epithelia except adult epidermis (1).