Immunization with a cannabinoid receptor type 1 peptide results in experimental allergic meningocerebellitis in the Lewis rat: a model for cell-mediated autoimmune neuropathology.

Neuronal elements are increasingly suggested as primary targets of an autoimmune attack in certain neurological and neuropsychiatric diseases. Type 1 cannabinoid receptors (CB1) were selected as autoimmune targets because they are predominantly expressed on neuronal surfaces in brain and display strikingly high protein levels in striatum, hippocampus, and cerebellum. Female Lewis rats were immunized with N-terminally acetylated peptides (50 or 400 microg per rat) of the extracellular domains of the rat CB1 and killed at various time points. Subsequent evaluation using immunohistochemistry and in situ hybridization showed dense infiltration of immune cells exclusively within the cerebellum, peaking 12-16 days after immunization with the CB1 peptide containing amino acids 9-25. The infiltrates clustered in meninges and perivascular locations in molecular and granular cell layers and were also scattered throughout the CB1-rich neuropil. They consisted primarily of CD4(+) and ED1(+) cells, suggestive of cell-mediated autoimmune pathology. There were no inflammatory infiltrates elsewhere in the brain or spinal cord. The results show that neuronal elements, such as neuronal cell-surface receptors, may be recognized as antigenic targets in a cell-mediated autoimmune attack and, therefore, support the hypothesis of cell-mediated antineuronal autoimmune pathology in certain brain disorders.