IL17A and neuromyelitis optica: Interestingly, there was a general positive correlation between HS and IFNγ, IL17A, and MMP1 concentrations in the CSF of NMO patients (IFNγ, p=0.004, r=0.570; IL17A, p=0.036, r=0.431; MMP1, p=0.024, r=0.460).