Ocrelizumab Modulates Both B and T Cell Immune Capacities in Multiple Sclerosis

To understand the molecular and cellular mechanisms beyond B-cell depletion with the anti-CD20 monoclonal antibody ocrelizumab, we used comprehensive muti-modal flow cytometry and functional assays in a prospective longitudinal multiple sclerosis (MS) cohort. Ocrelizumab depleted the vast majority of B cells and showed selective effects on different B cells subsets. Analysis of residual/replenished B cells revealed relative enrichment of regulatory B cells like CD27 ⁺ CD43 ⁺ B1 and CD24 ^hi CD38 ^hi transitional B cells, and reduction of CD27 ⁺ memory B cell subsets and CD19 ⁺ IgD ⁺ CD27 ⁻ naïve B cells at early time points (1-3 month) and before subsequent infusions at 4-7 months, 11-14 months, and >18 months. CD20+ T cells and peripheral helper T-cells (Tph) were also reduced. RNA sequencing analysis showed B1 cells have significantly higher expression of LGALS1 , KCNN4 , ITGB1 , and IL2RB . Compared to transitional B cells, B1 cells also displayed significantly higher expression of tissue homing molecules ITGAX (CD11c) , S100A4 , ITGB1 , and CXCR3 . IL10 signaling pathway is increased in these B cells. Ex vivo B cell functional assays indicated the residual/replenishing B cells were anergic following ocrelizumab, with increased IL10/TNFα and IL10/IL6 ratios under BCR stimulation. Ocrelizumab treatment may create a self-reinforcing regulatory circuit: the reduction of Tph cells could alleviate suppression of regulatory B cells, which subsequently expand and further promote regulatory T cell networks via IL2RB , LGALS1 , and an increased IL-10 signaling pathway.