Anti-CD1d Monoclonal antibody, clone 62.2 [PE]

B cells contribute to the pathogenesis of neuromyelitis optica (NMO) by producing Aquaporin 4-specific autoantibodies (AQP4-ab); on the other hand, there are certain B cells that suppress immune responses by producing regulatory cytokines, such as IL-10. In this study, we investigated the presence of IL-10-producing Breg cells among lymphocyte subsets. Twenty-two seropositive NMO spectrum disorder (NMOSD) patients (29 samples) and 13 healthy controls (HCs) (14 samples) were enrolled. All NMOSD patients have received one or more immunosuppressive drugs. The phenotype and frequency of B cell and T cell subsets in the peripheral blood were measured by flow cytometry. We defined Breg cells as IL-10-producing B (B10) cells, which are CD19(+)CD39(+)CD1d(+)IL-10(+). The potential relations were evaluated between specific lymphocyte subsets and AQP4-ab intensity measured by the cell-based indirect immunofluorescence assay. The frequency of B10 cells was higher in patients with NMOSD regardless of the disease status than that in HCs (attack samples; p = 0.009 and remission samples; p < 0.001, respectively). In addition, the frequency of IL-17(+) Treg cells among Treg cells was higher during remission than during an attack (uncorrected p = 0.032). Among the lymphocyte subsets, B10 cells alone showed a positive correlation with the intensity of AQP4-ab positivity (rho [rho] = 0.402 and p = 0.031). It was suggested that the suppressive subsets including B10 and IL-17(+) Treg cells might have important roles in controlling disease status in NMOSD. Further functional studies may help to elucidate the immunological role of B10 and IL-17(+) Treg cells in NMOSD.

Pro-inflammatory activity and cell-mediated immune responses have been widely observed in patients with major depressive disorder (MDD). Besides their well-known function as antibody-producers, B cells play a key role in inflammatory responses by secreting pro- and anti-inflammatory factors. However, homeostasis of specific B cell subsets has not been comprehensively investigated in MDD. In this study, we characterized circulating B cells of distinct developmental steps including transitional, na < ve-mature, antigen-experienced switched, and non-switched memory cells, plasmablasts and regulatory B cells by multi-parameter flow cytometry. In a 6-weeks follow-up, circulating B cells were monitored in a small group of therapy responders and non-responders. Frequencies of na < ve lgD(+)CD27(-) B cells, but not lgD(+)CD27(+) memory B cells, were reduced in severely depressed patients as compared to healthy donors (HD) or mildly to moderately depressed patients. Specifically, B cells with immune-regulatory capacities such as CD1d(+)CD5(+) B cells and CD24(+)CD38(hi) transitional B cells were reduced in MDD. Also Bm1-Bm5 classification in MDD revealed reduced Bm2' cells comprising germinal center founder cells as well as transitional B cells. We further found that reduced CD5 surface expression on transitional B cells was associated with severe depression and normalized exclusively in clinical responders. This study demonstrates a compromised peripheral B cell compartment in MDD with a reduction in B cells exhibiting a regulatory phenotype. Recovery of CD5 surface expression on transitional B cells in clinical response, a molecule involved in activation and down-regulation of B cell responses, further points towards a B cell-dependent process in the pathogenesis of MDD.