Myelin Basic Protein-Induced Production of Tumor Necrosis Factor-α and Interleukin-6, and Presentation of the Immunodominant Peptide MBP85-99 by B Cells from Patients with Relapsing-Remitting Multiple Sclerosis

B cells are involved in driving relapsing-remitting multiple sclerosis (RRMS), as demonstrated by the positive effect of therapeutic B-cell depletion. Aside from producing antibodies, B cells are efficient antigen-presenting and cytokine-secreting cells. Diverse polyclonal stimuli have been used to study cytokine production by B cells, but here we used the physiologically relevant self-antigen myelin basic protein (MBP) to stimulate B cells from untreated patients with RRMS and healthy donors. Moreover, we took advantage of the unique ability of the monoclonal antibody MK16 to recognize the immunodominant peptide MBP85-99 presented on HLA-DR15, and used it as a probe to directly study B-cell presentation of self-antigenic peptide. The proportions of B cells producing TNF-α or IL-6 after stimulation with MBP were higher in RRMS patients than in healthy donors, indicating a pro-inflammatory profile for self-reactive patient B cells. In contrast, polyclonal stimulation with PMA + ionomycin and MBP revealed no difference in cytokine profile between B cells from RRMS patients and healthy donors. Expanded disability status scale (EDSS) as well as multiple sclerosis severity score (MSSS) correlated with reduced ability of B cells to produce IL-10 after stimulation with MBP, indicative of diminished B-cell immune regulatory function in patients with the most severe disease. Moreover, EDSS correlated positively with the frequencies of TNF-α, IL-6 and IL-10 producing B cells after polyclonal stimulation. Patient-derived, IL-10-producing B cells presented MBP85-99 poorly, as did IL-6-producing B cells, particulary in the healthy donor group. B cells from MS patients thus present antigen to T cells in a pro-inflammatory context. These findings contribute to understanding the therapeutic effects of B-cell depletion in human autoimmune diseases, including MS

Cellular sources of dysregulated cytokines in relapsing-remitting multiple sclerosis

BACKGROUND: Numerous cytokines are implicated in the immunopathogenesis of multiple sclerosis (MS), but studies are often limited to whole blood (WB) or peripheral blood mononuclear cells (PBMCs), thereby omitting important information about the cellular origin of the cytokines. Knowledge about the relation between blood and cerebrospinal fluid (CSF) cell expression of cytokines and the cellular source of CSF cytokines is even more scarce. METHODS: We studied gene expression of a broad panel of cytokines in WB from relapsing-remitting multiple sclerosis (RRMS) patients in remission and healthy controls (HCs). Subsequently we determined the gene expression of the dysregulated cytokines in isolated PBMC subsets (CD4(+), CD8(+)T-cells, NK-cells, B-cells, monocytes and dendritic cells) from RRMS patients and HCs and in CSF-cells from RRMS patients in clinical relapse and non-inflammatory neurological controls (NIND). RESULTS: RRMS patients had increased expression of IFN-gamma (IFNG), interleukin (IL) 1-beta (IL1B), IL7, IL10, IL12A, IL15, IL23, IL27, lymphotoxin-alpha (LTA) and lymphotoxin-beta (LTB) in WB. In PBMC subsets the main sources of pro-inflammatory cytokines were T- and B-cells, whereas monocytes were the most prominent source of immunoregulatory cytokines. In CSF-cells, RRMS patients had increased expression of IFNG and CD19 and decreased expression of IL10 and CD14 compared to NINDs. CD19 expression correlated with expression of IFNG, IL7, IL12A, IL15 and LTA whereas CD14 expression correlated with IL10 expression. CONCLUSIONS: Using a systematic approach, we show that expression of pro-inflammatory cytokines in peripheral blood primarily originates from T- and B-cells, with an important exception of IFNG which is most strongly expressed by NK-cells. In CSF-cell studies, B-cells appear to be enriched in RRMS and associated with expression of pro-inflammatory cytokines; contrarily, monocytes are relatively scarce in CSF from RRMS patients and are associated with IL10 expression. Thus, our findings suggest a pathogenetic role of B-cells and an immunoregulatory role of monocytes in RRMS

Proportions of cytokine-producing B cells after polyclonal stimulation.

<p>Mononuclear cells from 12 healthy donors (HD) and 13 relapsing-remitting multiple sclerosis (RRMS) patients were stimulated with myelin basic protein (MBP) for 24 hours, and with PMA + ionomycin for the last 4 hours of incubation. Cells were stained intracellularly with antibodies against (A) TNF-α, (B) IL-6 and (C) IL-10, and assessed by flow cytometry. Shown are the proportions of CD19+ B cells producing these cytokines; the corresponding values for unstimulated cell cultures have been subtracted. Box plots indicate median, interquartile range (box) and range (whiskers).</p

Association between MBP-induced cytokine production by B cells and disease severity.

<p>Mononuclear cells from 12 relapsing-remitting multiple sclerosis patients were stimulated with myelin basic protein (MBP) for 24 hours, stained for content of (A and D) TNF-α, (B and E) IL-6, or (C and F) IL-10, and assessed by flow cytometry. The proportion of cytokine-producing B cells adjusted for background (un-stimulated cells) is shown as a function of the Expanded Disability Status Scale (EDSS; upper row) and the Multiple Sclerosis Severity Score (MSSS; lower row)(both missing for one patient). Spearman’s correlation coefficient (R_S) and the corresponding <i>p</i>-values are also shown.</p

relapsing-remitting multiple sclerosis

Background: Numerous cytokines are implicated in the immunopathogenesis of multiple sclerosis (MS), but studies are often limited to whole blood (WB) or peripheral blood mononuclear cells (PBMCs), thereby omitting important information about the cellular origin of the cytokines. Knowledge about the relation between blood and cerebrospinal fluid (CSF) cell expression of cytokines and the cellular source of CSF cytokines is even more scarce. Methods: We studied gene expression of a broad panel of cytokines in WB from relapsing-remitting multiple sclerosis (RRMS) patients in remission and healthy controls (HCs). Subsequently we determined the gene expression of the dysregulated cytokines in isolated PBMC subsets (CD4 +, CD8 + T-cells, NK-cells, B-cells, monocytes and dendritic cells) from RRMS patients and HCs and in CSF-cells from RRMS patients in clinical relapse and noninflammatory neurological controls (NIND). Results: RRMS patients had increased expression of IFN-gamma (IFNG), interleukin (IL) 1-beta (IL1B), IL7, IL10, IL12A, IL15, IL23, IL27, lymphotoxin-alpha (LTA) and lymphotoxin-beta (LTB) in WB. In PBMC subsets the main sources of pro-inflammatory cytokines were T- and B-cells, whereas monocytes were the most prominent source of immunoregulatory cytokines. In CSF-cells, RRMS patients had increased expression of IFNG and CD19 and decreased expression of IL10 and CD14 compared to NINDs. CD19 expression correlated with expression of IFNG, IL7, IL12A

MBP-induced cytokine production by B cells.

<p>Mononuclear cells from 12 healthy donors (HD) and 13 patients with relapsing-remitting multiple sclerosis (RRMS) were stimulated with whole myelin basic protein (MBP) for 24 hours and stained intracellularly for (A) TNF-α, (B) IL-6, and (C) IL-10 before assessment by flow cytometry. The proportions of CD19+ B cells producing these cytokines are shown as median, interquartile range (box) and range (whiskers), adjusted for background (positive events in unstimulated cell cultures). In some cases these numbers were larger than in MBP-stimulated cultures, hence negative values. <i>p</i>-values indicate the probability of no difference between the groups (two-tailed Mann Whitney U-test) or from zero (Wilcoxon signed-rank test).</p