Endosomal TLRs govern disease-stage specific B cell responses in Sjogren’s disease 2257833

Introduction Sjogren’s disease (SD) is a systemic autoimmune disease that occurs primarily in women. While B cells play an essential role in SD, the molecular mechanisms that govern B cell activation and the striking female disease predilection remain unclear. Using a mouse model of SD, termed NOD.B10, we showed that endosomal Tlrs govern disease in a sex-biased manner, as Tlr7 drove disease in females and systemic ablation of Tlr9 resulted in an increased percentage of splenic B cell subsets that are implicated in autoimmunity, such as germinal center and age-associated B cells. This B cell expansion was diminished in age- and sex-matched NOD.B10 females that lacked systemic expression of both Tlr7 and Tlr9. Based on these data, we hypothesized that Tlr7 and Tlr9 orchestrate disease-stage-specific B cell responses in SD. Methods We performed single-cell RNA sequencing on salivary glands from NOD.B10 females at the clinical disease stage, and observed that Tlr7 and Tlr9 expression was enriched in SD B cells. We then used flow cytometry to assess splenic B cell activation in NOD.B10 strains with clinical disease. Results Our data revealed that the percentage of activated B cells (B220+CD69+) was increased in NOD.B10Tlr9-/- females as compared to NOD.B10 mice, and this was dependent on Tlr7. No differences in B cell activation were observed in any of the male strains. To determine if B cells from NOD.B10 females showed differences in sensitivity to Tlr9 agonism with disease progression, we isolated spleens from pre-disease, clinical disease, and advanced disease stage mice and age- and sex-matched controls and cultured them with CpG-B. SD B cells were hyperresponsive to CpG-B at pre-disease and clinical disease time points, while no differences in CD69+ expression were observed at the advanced disease stage. Conclusion Overall, our study revealed that Tlr9 governs B cell activation in SD females in a Tlr7-dependent manner and SD B cells show differential sensitivity to Tlr9 at distinct disease stages.