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Background: Neuromyelitis optica (NMO) is a neurological disease characterized by optic neuritis and transverse myelitis with long spinal cord lesion. Recently, NMO-IgG, which recognizes the aquaporin-4 (AQP-4), was identified in sera from patients with NMO. AQP-4 is a water channel expressed in astrocytes and ependymal cells throughout the brain and spinal cord. Immunopathological study showed a loss of AQP-4 immunoreactivity in NMO lesions. Whether NMO is a distinct disease entity or a variant of multiple sclerosis (MS) has been discussed. The goal of the study is to clarify differences in lymphocyte subsets in cerebrospinal fluid (CSF) and peripheral blood lymphocytes between NMO and MS. Methods and results: Anti AQP-4 antibody was examined by an immunohistochemical detection system using AQP-4 transfected human embryonic kidney (HEK293) cell line. Using flow cytometry, we analyzed CD4, CD8, CD20, CD4+CD25+, CD8+ CD11a+ cells in CSF and peripheral blood samples from 18 patients with relapsing and remitting MS (R-R MS), 18 patients with NMO, and 14 patients with other neurological diseases (OND). All NMO patients showed long spinal cord lesions and were positive for anti AQP-4 antibody. In peripheral blood, a significant decrease in CD8+CD11a+ cells was observed in R-R MS (stable state) compared with that in NMO or OND (MS:3.4?2.3, NMO:10?7.7, OND:8.8?3.2. P less than 0.05). There was no significant difference in the percentage of CD8+CD11a+ cells between NMO and OND. Conclusion: cytotoxic CD8+ T cell in peripheral blood in stable R-R MS is significantly decreased but not in NMO. Our findings indicated that cytotoxic CD8+ T cell may play a different role in MS and NMO.

Read More: Flow cytometric analysis of lymphocyte subsets in cerebrospinal fluid and peripheral blood of patients with multiple sclerosis and neuromyelitis optica