Local hypertrophic/hyperplastic changes of keratinizing squamous epithelium of pinna induced by concanavalin A and other immunomodulators in mice.

Intradermal administration of concanavalin A, a potent T-cell mitogen, into an ear lap resulted in activation of chondrogenesis and stimulation of epidermis proliferation. This proliferation is sometimes invasive in character (pearls and epidermal nests form in the underlying connective tissue) but never turns into true cancerous lesions. This reaction can be delayed, but not prevented, by the prostaglandin inhibitor indomethacin. Stimulation of epidermis proliferation was also caused by administration of other immunomodulators, such as carrageenan type IV, Moloney sarcoma development, and rarely in the course of GvHr, but to much lesser degree than with concanavalin A. It is suggested that the same growth factors, which are mediators of local chondrocyte stimulation, are also mediators of keratinocyte activation.