CD180 Expression on B Cells in Primary Sjogren's Syndrome Mice

Objectives:
Primary Sjogren’s syndrome (pSS) is an autoimmune disease. The etiology of pSS is poorly understood and no curative treatments are available. Thus, there is a need to identify the causes of pSS to improve treatments. B cell abnormalities are well documented in pSS, and therapies that target B cells may have therapeutic utility. Mature B cells express a receptor termed CD180 that promotes B cell proliferation and protects against apoptosis. Preliminary work shows CD180-deficient B cells are increased in salivary tissue and peripheral blood of patients with SS. Additionally, ligation of Toll-like receptor 7 (TLR7) reduces CD180 expression in healthy mice, although this has not been studied in the context of pSS. The objective of this study was to evaluate whether B cell CD180 levels differ between pSS mice and controls, and to determine if TLR7 agonism diminishes CD180 expression by B cells in pSS.
Methods: We used a pSS mouse model and age and sex-matched controls. Cells were harvested from females at the pre-disease and clinical disease stages and CD180 expression on B cells derived from splenic follicular and marginal zone subsets, cervical lymph nodes, and peritoneal B1a cells was assessed using flow cytometry. B cells were also cultured in the presence or absence of the TLR7 agonist imiquimod, and flow cytometry was performed to assess CD180 expression.
Results:
CD180 was expressed on all B cell subsets from both pSS and control mice. No differences were observed in B cell CD180 expression between the strains at either time point. TLR7 agonism altered B cell CD180 expression in pSS mice.
Conclusions:
Our preliminary data demonstrate CD180 is expressed in pSS mice at both pre-disease and clinical disease time points and TLR7 agonism alters CD180 expression in distinct B cell subsets. Further studies are needed to determine how CD180 contributes to pSS pathogenesis.