Autoimmune encephalitis in humans: how closely does it reflect multiple sclerosis ?

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system. Immunological studies suggest that it is a T-cell mediated autoimmune disease, although an MS-specific target antigen for autoimmunity has so far not been identified. Models of experimental autoimmune encephalomyelitis in part reproduce features of MS, but none of the models so far covers the entire spectrum of pathology and immunology. Autoimmune disease of the nervous system has occasionally been observed in humans after active sensitization with brain tissue or brain cells, giving rise to acute demyelinating polyradiculoneuritis, acute disseminated encephalomyelitis and in rare cases reflecting an inflammatory demyelinating condition similar to acute multiple sclerosis. In this study we analyzed in detail the immunopathology in archival autopsy tissue of a patient who died with an MS like disease after repeated exposure to subcutaneous injections of lyophilized brain cells.

The pathology of this patient fulfilled all pathological diagnostic criteria of MS. Demyelination and tissue injury was associated with antibody (IgM) deposition at active lesion sites and complement activation. Major differences to classical EAE models were seen in the composition of inflammatory infiltrates, being dominated by B-cells, infiltration of IgM positive plasma cells, profound infiltration of the tissue by CD8⁺ T-lymphocytes and a nearly complete absence of CD4⁺ T-cells.

Our study shows that auto-sensitization of humans with brain tissue can induce a disease, which closely reflects the pathology of MS, but that the mechanisms leading to demyelination and tissue injury differ from those, generally implicated in the pathophysiology of MS through studies in experimental autoimmune encephalomyelitis.