A monoclonal antibody specific for an epidermal cell antigen of Xenopus laevis: electron microscopic observations using a gold-labeling method.

A monoclonal antibody (EPI-1), raised against the supernatant of a homogenate of Xenopus laevis larvae at the tailbud stage (stage 36/37), interacts specifically with a 250 KD epidermal antigen of Xenopus. An immunocytochemical gold-labeling technique was used to investigate changes in antigen distribution during epidermal development of Xenopus laevis. Specific immunolabeling was initially detected over the endoplasmic reticulum in the outer epithelial cells of the late gastrula stage (stage 12.5). After the early neurula stage (stage 13), immunolabeling appeared over moderately electron-dense bodies (these bodies disappear after stage 29), and also over the apical cell surface and adjacent cytoplasm of all the outer epithelial cells. During metamorphosis, labeling decreased and disappeared after stage 62, as the superficial layer had peeled off. These data suggest that the antigen is useful as a marker of general differentiation in studies of epidermal development during the embryonic and larval stages of Xenopus laevis.