Opticospinal multiple sclerosis in Japanese

Antibodies to aquaporin-4 (AQP4) are found in a number of Japanese opticospinal multiple sclerosis (OSMS) patients. Whether anti-AQP4 antibody-positive and -negative OSMS patients are afflicted with an identical disease remains unknown. To clarify immunological differences between the two groups of patients, we studied serum antibody titres against AQP4 in 191 patients with idiopathic central nervous system demyelinating diseases and clarified any relationships with immunological parameters. The anti-AQP4 antibody positivity rate was higher in patients with OSMS (36.2%), idiopathic recurrent myelitis (23.5%), and recurrent optic neuritis (26.9%) than in conventional MS patients (8.0%), and those with other diseases (0%). Anti-AQP4 antibody titre was significantly higher in patients with SS-A/B antibodies than in those without. Anti-AQP4 antibody-negative OSMS patients showed significantly higher CD4⁺IFN-γ⁺IL-4-T cell percentages and intracellular IFN-γ/IL-4 ratios than anti-AQP4 antibody-positive patients, anti-AQP4 antibody-negative conventional MS patients, and healthy controls. As well, CD4⁺IFN-γ ⁺IL-4-T cell percentages were negatively correlated with anti-AQP4 antibody titres. In CSF, OSMS patients had significantly higher levels of IFN-γ and granulocyte colony-stimulating factor levels than patients with non-inflammatory neurological diseases and other causes of myelitis. A significant increase of IL-17 compared with non-inflammatory neurological diseases patients was only found in OSMS patients, irrespective of the presence or absence of anti-AQP4 antibody. These findings suggest that high titres of anti-AQP4 antibodies are produced as a result of heightened humoral autoimmunity, and that they are likely to contribute to extensive lesion development through disturbed resolution of vasogenic oedema. Moreover, since intrathecal up-regulation of IL-17 and IFN-γ is characteristic of OSMS, Th17/ Th1 cells may be critical for the initiation of inflammation and the disruption of blood-brain barrier (BBB); rendering anti-AQP4 antibody get across the BBB.