Moreover, the serum concentrations of CXCL6/GCP-2, Midkine and C5/C5a are significantly altered between AQP4-positive NMO and MOG-positive NMO cases, which indicates different immunological mechanisms of NMO pathogenesis that are associated with these two kinds of antibodies 22. The gene discussed is CXCL6; the disease is neuromyelitis optica.