S-100 antigen in satellite cells of the adrenal medulla and the superior cervical ganglion of the rat. An immunochemical and immunocytochemical study.

Measurable amounts of the nervous-system specific S-100 protein were detected by microcomplement fixation assay both in the superior cervical ganglion and in the adrenal medulla of adult rats, though at a significantly higher concentration in the ganglion. By the unlabeled antibody PAP method, the antigen was localized at the ultrastructural level in the Schwann cells and in the satellite cells of the ganglion, but not in neurons. Similarly, the protein was found in the Schwann cells of the adrenal medulla, but not in the chromaffin cells. Moreover, the S-100 immunolabeling allowed detection of a class of "satellite" cells closely enveloping the chromaffin cells. In the labeled cells of both organs the reaction product was diffusely distributed in the cytoplasmic matrix as well as in the nucleoplasm. The presence of the S-100 antigen in the satellite cells of the sympathetic ganglion and in "satellite" cells of the adrenal medulla suggests a possible homology for the two cell types, and one could hypothesize the presence in peptide hormone-secreting endocrine organs of glia-like cells exhibiting functional relationships with the secretory cells comparable to those of the glial cells with the neurons.