Characterization of antibodies against major fish CNS myelin proteins: immunoblot analysis and immunohistochemical localization of 36K and IP2 proteins in trout nerve tissue.

Antisera against the trout CNS myelin proteins 36K and IP2 were prepared in rabbits and characterized by immunoblot analysis and immunohistochemistry. The anti-36K antiserum exclusively stained its corresponding antigen from trout CNS myelin but failed to recognize any myelin polypeptide from either trout PNS or mammalian CNS and PNS. Antibodies against the IP2 glycoprotein specifically cross-reacted with related intermediate proteins (IP) of both CNS and PNS myelin from trout but only faintly labeled the PO protein of mouse peripheral nerve. Immunohistochemical localization of both antigens in the CNS of young trout was confined to the myelin sheath, except that anti-36K antiserum also stained oligodendrocytes. Nodes of Ranvier, neuronal cell bodies, and dendrites, as well as other glial elements, were negative. Specificity of the immunofluorescent reaction was established by crossed immunoadsorption experiments. Whereas on adjacent sections through trout brain both antigens exhibited a nearly identical distribution pattern, immunostaining in peripheral nerves was seen only with anti-IP2 antibodies.