Antibodies to orthokeratotic keratinocytes in monitoring the drug-induced inhibition of parakeratotic differentiation in adult and infant mice.

Parakeratosis (PK) is a common feature of the abnormal epidermis in several disorders of keratinization. Tar phenols, retinoids and steroids which cause the inhibition of PK and the restoration of orthokeratosis (OK) are used for treating psoriasiform conditions. In this work, we studied two experimental models of the drug-induced inhibition of PK: (1) the suppression of the normal development of PK in the infant mouse tail and (2) the OK conversion of established PK in the adult tail. Two markers of OK were studied: the histological evaluation of the granular layer and the expression of cytoplasmic antigens linked to OK differentiation. It was demonstrated that high-boiling tar phenols cause a more potent inhibition of PK than betamethasone valerate. Most importantly, immunofluorescence showed that the switch to OK differentiation was located in the cells situated in a suprabasal position. The use of these immunological markers to investigate and anti-parakeratotic mechanisms has revealed that these drugs act at stages of keratinocyte differentiation which are distinct from those previously suggested.