Objective:  To detect the proportion of CD1d(hi)CD5(+)CD19(+) regulatory B cells (Bregs) in peripheral blood of the patients with neuromyelitis optica (NMO), and explore whether CD1d(hi)CD5(+)CD19(+) Bregs can play a role as a biomarker in the diagnosis of NMO versus multiple sclerosis (MS).

Methods:  Flow cytometry was performed to detect the proportion of CD1d(hi)CD5(+)CD19(+) Bregs in peripheral blood from 44 cases of NMO, 38 cases of MS, and 30 healthy controls. The serum level of aquaporin-4 antibody (AQP4-Ab) of patients with NMO was detected by indirect immunofluorescence assay.

Results:  The proportion of CD1d(hi)CD5(+)CD19(+) Bregs in CD19(+) B cells and lymphocytes was significantly lower in NMO group than in MS and control groups; however, there was no significant difference between MS group and control group. The proportion of CD1d(hi)CD5(+)CD19(+) Bregs in CD19(+) B cells and lymphocytes was lower in AQP4-Ab-positive NMO patients than in AQP4-Ab-negative NMO patients, and the difference was statistically significant. Conclusion CD1d(hi)CD5(+)CD19(+) Bregs may be a biomarker in the differential diagnosis of NMO versus MS.