The Longitudinal Effect of Rituximab in Primary SjöGren’s Syndrome.

Objectives: Assess the effects of rituximab on salivary gland (SG) histopathology and systemically on the T-cell compartment in the Trial for Anti-B-Cell Therapy in patients with primary Sjögren’s Syndrome (TRACTISS) cohort.
Methods: 26 subjects randomised to rituximab or placebo consented for SG biopsy at baseline, weeks 16 and 48. Biopsies were fluorescently assessed for B-cells (CD20+), T-cells (CD3+), follicular dendritic cells (FDCs) (CD21+) and plasma cells (CD138+). Digital imaging analysis and semi-quantitative grading quantified SG inflammation. RNA extracted from matched SGs underwent sequencing and gene signature-based analysis (xCell) to infer 64 immune cell types. Matched sera were assessed for T-helper cytokines and B-lymphocyte chemoattractant (CXCL13) using LEGENDplex^TM and ELISA immunoassays, respectively.
Results: Two cycles of rituximab prevented new B-cell infiltration, development of FDC networks within SG inflammatory aggregates and ectopic GC organisation at 48 weeks. Gene enrichment analysis (xCell) demonstrated a prevention of class-switched- and memory B-cell infiltration by rituximab, with no effect on T-cells or plasma cells. The reduction of ELS organisation was confirmed by transcriptomic analysis showing a downregulation of lymphocyte recruitment and ectopic GC organisation genes, such as CXCL13, CCR7, CCL19 and LTβ. The analysis of placebo SGs transcriptomics at week 48 showed a higher expression of ectopic GC organisation genes in females compared to male subjects, suggesting a gender-driven difference in SG inflammation progression. Peripheral markers of salivary gland inflammation and SG GC organisation, such as CXCL13, were reduced after Rituximab, together with T-cell cytokines IFN-g, IL-4, IL-17F, IL-21, known to be involved in ectopic lymphomagenesis.
Conclusions: Rituximab preserves residual SG function by preventing worsening SG inflammation and ELS formation compared to placebo, by affecting FDC network development and downregulating genes involved in B-cell migration and organisation. These results reflect the clinical improvement of unstimulated whole salivary flow observed at week 48 in rituximab-treated patients in the TRACTISS trial.