LOCALIZATION OF THE NEURONAL ANTIGEN RECOGNIZED BY ANTI-TR ANTIBODIESFROM PATIENTS WITH PARANEOPLASTIC CEREBELLAR DEGENERATION AND HODGKINS-DISEASE IN THE RAT NERVOUS-SYSTEM

Patients with paraneoplastic cerebellar degeneration and Hodgkin's dis ease develop autoantibodies (Tr-Ab) that immunoreact with the cytoplas m of the Purkinje cells and produce a characteristic punctate pattern in the molecular layer of the cerebellum. In the present study, we ana lyzed the structures of the adult rat cerebellar cortex identified by Tr-Ab and the expression of the antigen recognized by Tr-Ab in the dev eloping rat brain. By laser confocal microscopy and immunoelectron mic roscopy, Tr-Ab immunoreactivity was found localized in the cytosol and outer surface of the endoplasmic reticulum of the perikarya of neuron s of the molecular layer and the cell body and dendrites of Purkinje c ells without a particular concentration in dendritic spines. Tr-Ab rea ctivity was more widespread in the developing rat brain. Tr-Ab labelin g of Purkinje cells was already observed at PO (day of birth). The sta ining of the molecular layer followed the development of the dendritic tree. The internal and inner level of the external granule cell layer were labeled with Tr-Ab with a dotted pattern that became almost nega tive by the 2nd postnatal week. The staining probably corresponded to granule cells as suggested by the positive Tr-Ab labeling of cultures of embryonic granule neurons. The present findings suggest that the an tigen recognized by Tr-Ab appears early and is widely expressed in the developing rat brain. In the adult cerebellum, the antigen is localiz ed in the cell body and dendrites of the Purkinje cells but is not con centrated in the dendritic spines.