The neuroendocrine thymus. Abundant occurrence of oxytocin-, vasopressin-, and neurophysin-like peptides in epithelial cells.

Certain subtypes of thymic epithelial cells--the medullary epithelium, the cortical surface epithelium, and some intracortical epithelial cells--show strong immunohistochemical reactivity with antisera against oxytocin, Arg-vasopressin and neurophysin. The epithelial nature of the neuropeptide containing cells is shown by their morphology and their reactivity with monoclonal anti-cytokeratin AE1/E3. Hassall's corpuscles are positive as well. The immunoreactivity patterns for the three neuropeptides are identical, suggesting a parallel distribution. The vast majority of cortical epithelial cells are negative, emphasizing the tightly controlled microenvironment for T-cell development. The possibility of a neuroendocrine role of the thymus is discussed.