Granular layer induction following the topical application of proliferating agents.

Evidence is provided for a possible dermal influence on the epidermis. Topical vitamin A stimulates a number of dermal cells with different enzyme reactions, and these invade the epidermis at about the time a granular layer is induced in mouse tail scale epidermis. N-hexadecane also induced a granular layer formation in the tail scale epidermis but the application of this agent only results in the invasion of the epidermis by non-specific esterase cells. These non-specific esterase cells are present in the follicular zone where a granular layer is usually present. It appears that dendritic cells may be responsible for the formation of a granular layer and that these cells in some way influence the keratinocytes to discharge their lyosomal enzymes and thus form a granular layer. It appears unlikely that the dendritic cells actually contribute their own acid hydrolases to the cell cytolysis necessary for the production of granular layer.