IMMUNOCYTOCHEMICAL STUDY WITH AN ANTITRANSFERRIN BINDING-PROTEIN SERUM - A MARKER FOR AVIAN OLIGODENDROCYTES

We have investigated immunocytochemically the localization of a transf errin binding protein (TfBP) in adult CNS of avian and mammalian speci es using a polyclonal antibody raised against the protein purified fro m hen oviduct membranes (alpha OV-TfBP). TfBP has recently been shown to be HSP108. An overall strong immunoreactivity was revealed in most parts of the avian brains, especially in the white matter. The main im munoreactivity originated in small, intensively reacting cells interpr eted as oligodendrocytes. The density of TfBP-labeled oligodendrocytes of the avian brains was generally proportional to the degree of myeli nation. There were no marked differences in TfBP-immunostaining patter n between avian species (chick, pigeon and lovebird). On the other han d, in rat, rabbit and cat brains we could not find any TfBP-immunoreac tivity. Immunoelectron microscopy has further revealed that TfBP is pr esent in the light and medium types of oligodendrocytes which are know n to have high metabolic activities. TfBP reaction product was homogen eously dispersed throughout the perinuclear cytoplasm and fine process es of oligodendrocytes. The intracytoplasmic organelles such as mitoch ondria and Golgi apparatus were devoid of reaction product. The presen ce of TfBP in oligodendrocytes implies that this protein may play an i mportant role in transferrin-mediated iron metabolism in the CNS. The complete lack of cross-reactivity between alpha OV-TfBP and mammalian tissues suggests that there is species variability in TfBP structure. We conclude that this chick TfBP antiserum will prove useful in studie s of oligodendrocytes and myelination in the avian CNS.