The role of b cells in the early onset of the first demyelinating event of acute optic neuritis

Purpose. We evaluated the molecular pathways that operate in the early phase of acute optic neuritis (ON) by studying gene expression profiles of peripheral blood mononuclear cells (PBMCs) subpopulations, including CD19⁺ B cells, CD14+ macrophages, and CD4+ and CD8+ T cells. Methods. Samples of PBMC subpopulations were obtained from 18 MS patients within 96 hours of the acute onset of the first demyelinating event of ON, and from 14 age- and sex-matched healthy subjects. High throughput gene expression analysis was performed on samples from six ON patients and nine healthy subjects using Affymetrix technology. Data were analyzed using Partek software, and most informative genes (MIGs) were defined as genes with P < 0.01 and fold change > 2.0. Molecular pathways were analyzed by Ingenuity software. Verification of key MIGs was done on samples from five independent ON patients and five healthy subjects by quantitative (Q) RT-PCR and Western blot. Functional assay to test antigen presentation ability of sorted B cells was performed on blood samples from seven additional ON patients. Results. Significantly differentiating gene expression signatures consisting of 467, 55, and 55 MIGs respective of CD19⁺, CD14+, and CD4+ cells, were identified between ON and healthy subjects. No MIGs were detected for CD8+ cells. The major involvement of CD19⁺ B cells in the early stage of ON was characterized by enrichment of genes involved in activation of immune mechanisms (P — 3.2 X 10~²⁵ to 2.5 X 10~³), including cellular immune response (P — 7.1 X 10~¹²), B-cell cellular growth and proliferation (P — 1.0 X 10~⁷), activation of immune cells trafficking pathways (P — 5.4 X 10~¹⁵ to 2.0 X 10~³), and stimulation of antigen presentation (P — 8.9 X 10~¹¹). This massive B-cell-restricted initiation of the immune response in the early disease process of ON was followed by low CD14+ and CD4+ cells activity and CD8+ cells anergy Conclusions. Our findings demonstrate that CD19⁺ B cells have a significant role in the pathogenesis of the first demyelinating event of acute ON and suggest their role as a possible target for immunomodulation.