Neuromyelitis optica (NMO) is an inflammatory, demyelinating disease of the central nervous system characterized by the association of a serious myelitis and unilateral or bilateral optic neuritis. The present study aimed to analyze the immunological parameters of NMO patients with diagnosis established based on Wingerchuck et al. (1999) criteria. Production of IgG and IgA antibodies to antigens of MBP, PLP 95-116, MOG 92-106, and the cytokines interleukin-4 (IL-4) and interferon-gamma (INF-gamma) were assessed by Elisa assay. The cohort was formed by 28 NMO patients and a matched healthy control group. NMO patients had significant high levels of IgG to MOG (p<0.0001), PLP (p=0.0002) and MBP (p<0.0001), and solely IgA to MBP (p<0.0001). INF-gamma (p=0.61) levels were similar to healthy controls. Increased production of IL-4 (p=0.0084) indicates an important role for this cytokine in the activation of Th2 regulatory cells and of the IgA producers B lymphocyte indicating activation of humoral immunity.