Using the peroxidase anti-peroxidase immunocytochemical technique, neuron-specific enolase (NSE)-like immunoreactivity (NSE-LI) was revealed in Leydig cells of adult human testes at the light microscopic level. Differences in the NSE staining intensity were observed between the individual Leydig cells, separate cell groups within a testis and between the testes of individual patients. Together with the already established substance P-like immunoreactivity (SP-LI), the results obtained provided further evidence for the possible neuroectodermal origin of human Leydig cells and their presumable relation to the APUD- or the Diffuse Neuroendocrine System (DNES).
