Immunohistochemical study of the blood-brain barrier. Production of an artifact

The permeability to normal serum proteins of blood vessels in the central nervous system (CNS) was studied by means of the peroxidase-antiperoxidase immunohistochemical technique. Frozen sections were cut in a cryostat and then fixed briefly in 95% ethanol. The localization of serum proteins outside blood vessels in the brain was shown to be an artifact produced during the preparation of cryostat sections. It was concluded that such cryostat sections are unsuitable for studies of vascular permeability in the CNS.