Immunolocalization of dipeptidyl aminopeptidase (DAP IV) in the developing human brain

By means of immunohistochemical techniques we have investigated the presence of dipeptidyl aminopeptidase IV immunoreactivity in brain material derived from human fetuses, new‐borns and aged persons. It was revealed that the enzyme protein is abundantly present in the immature human CNS. On the contrary the adult human brain contains much less dipeptidyl aminopeptidase immunoreactivity. It is speculated that the enzyme might play an important role in neuronal proliferation and/or differentiation especially with regard to its possible action on certain neuronotrophic peptides (IGF II, growth hormone).