Localization of the P2 protein in peripheral nerve myelin.

The P2 protein was localized in frozen sections of peripheral nerve myelin from rabbit sciatic nerve and dorsal root and subpial areas of normal spinal cord as shown by strong immunofluorescence byu sing goat antirabbit P2 protein serum and fluorescein-labeled F(ab’)2 fragments prepared from rabbit anti-goa Itg G. No fluorescence was observed in rabbit brain with this technique, and only a very weak fluorescencwe as observed with spinal cord white matter, the significance of which is uncertain. Identical results were found when highly purified rabbit anti-P2 IgG, prepared by affinity chromatography, was used, or F(ab’)2 fragments therefrom. In every case, the fluorescence was abolished by prior treatment with P2 protein but not with basic protein. Anti-basic proteinw as not detected in the anti-P2 serrum either by immunodiffusion or radioimmune assay. The anti-Pt serum appeared highly specific because it showed only a single line on immunodiffusion with acid extracts of sciatic nerve from bovine, human, and guina pig as well as rabbit sources. Thesree sults show that P2 protein is exclusive to peripheral nerve myelin and is absent from central nervous system myelin; that from spinal cord is derived from subpial areas that interface with nerve rootlets.