Immunocytochemical localization of plasma proteins in neuronal perikarya

The presence of naturally occurring plasma proteins in the cell bodies of some neurons whose axons project outside the central nervous system was sought using the peroxidase-antiperoxidase (PAP) immunocytochemical technique. Rabbit antisera to whole rat serum and rat albumin were used as the primary antisera. The finding of immunoperoxidase reaction product within the perikarya is indicative of the presence of plasma proteins. It is suggested that the endocytosis and retrograde transport of exogenous protein tracers by neurons is paralleled by the neuronal incorporation of naturally occurring plasma proteins.