Complement activation in patients with neuromyelitis optica

- C3a levels were higher in NMO subjects compared to healthy controls.
- C3a levels correlated with neurological disability and levels of AQP4-IgG.
- C3a levels were higher during relapses than during remission periods in NMO patients.
- NMO patients had increased anti-C1q levels when compared to MS and healthy controls.

The role of complement has been demonstrated in experimental models of neuromyelitis optica (NMO), however, only few studies have analysed complement components longitudinally in NMO patients. We measured serum or plasma concentrations of anti-C1q antibodies and complement split products C3a and C4a and soluble C5b-9 in patients with NMO, multiple sclerosis and healthy controls. NMO patients had higher levels of C3a and anti-C1q antibodies than healthy controls. C3a levels correlated with disease activity, neurological disability and aquaporin-4 IgG in NMO patients suggesting a role of the alternative pathway of complement in the pathogenesis of NMO and supporting the strategy of therapeutic complement inhibition.