Comprehensive analysis of the intrathecal B-cell response in patients with multiple sclerosis

OBJECTIVE: To better understand the cerebrospinal fluid [CSF] antibody repertoire and its correlation with disease in patients with MS.

BACKGROUND: The presence of CSF IgG oligoclonal bands is one of the diagnostic hallmarks in MS and signifies the importance of the B-cell response in the disease. Recently, the success of anti B-cell treatment has further validated this observation. However, the specific role played by B-cells in the pathogenesis of the disease has not been elucidated. We undertook a comprehensive humoral immune response CSF analysis to better define the intrathecal antibody response in patients with MS.

METHODS: In a continuing study, CSF was obtained by standard lumbar puncture by an IRB-approved protocol. In ten patients with the most robust B-cell response, a comprehensive analysis was done. This includes determining CSF B/plasma cell isotype (IgG or IgM) using single cell florescence activating cell sorting (FACS) and polymerase chain reaction (PCR). CSF was also analyzed by ELISA for IgG levels, IgM levels, B-cell activating factor (BAFF), and CXCL13. Correlations were determined using the statistical program GraphPad Prism. Due to low sample numbers, non-parametric analyses were performed.

RESULTS: No correlation was found between B-cell isotypes and their respective antibody types. Neither IgG nor IgM antibody levels correlated with BAFF. IgM levels did not correlate with CXCL13. However, IgG levels significantly correlated with CXCL13 (Spearman r = 0.8424, p = 0.0037). CSF with higher IgM B-cells repertoire did not show correlation with CXCL13. However, there was significant positive correlation of percentage of IgM cells present in CSF with BAFF (Spearman r = 0.8667, p = 0.0022).

CONCLUSION: Our data shows that there is a correlation between IgG production and CXCL13 levels in CSF. In contrast, IgM B-cells appear to be correlated with BAFF levels. This suggest that the mechanisms underlying the B-cell response in CSF are dependent on the antibody isotype.