Expression of the WE3 antigen in newt epithelium originating from subcutaneous grafts of skin.

mAb WE3 recognizes an antigen that is developmentally regulated in the wound epithelium of regenerating newt limbs. The antigen is precociously expressed when pieces of WE3-negative wound epithelium are grafted subcutaneously (Tassava et al.: Recent Trends in Regeneration Research. New York: Plenum Publishing Co., pp. 37-49, 1989). In the present study, we investigated whether the WE3 antigen is expressed in epidermis of subcutaneous grafts of skin. Small pieces of limb skin were grafted into small tunnels in the lower jaw, limb, and tail, oriented either the same as (epidermis facing out) or opposite to (epidermis facing in) the orientation of the host skin. In most cases, the epithelium migrated from the graft along the wounded surface of the tunnel, closed onto itself, and formed a multilayered "emigrant" epithelium. Infrequently, the migrating epithelium combined with the wound epithelium of the insertion wound. In no case did the epithelium migrate over the cut edge of the grafted dermis. Reactivity to mAb WE3 was first seen at 4 days after grafting, when the migrating epithelium had almost closed over onto itself. By 6 days and thereafter, the entire emigrant epithelium was reactive to mAb WE3. While initially restricted to the emigrant epithelium, at 10 days after grafting and thereafter, reactivity was also seen in the epidermis that remained in contact with the dermis. Expression of the WE3 antigen was not influenced by the orientation of the graft nor by the graft site. The results show that, compared to amputated limbs, the epithelium originating from these grafts precociously expresses the WE3 antigen. Also, epidermis of grafted skin is capable of expressing the WE3 antigen.