TLR-7 activation induces lupus-like phenotype in C57BL/6 mice: a study on the immunological consequences of chronic Imiquimod exposure

San Luis

Congreso; LXXI Reunión Anual de la SAI.; 2023

Sociedad Argentina de Inmunologia

The critical role of Toll-like receptors (TLR) in the pathogenesis of Systemic LupusErythematosus (SLE) has been the subject of diverse investigations over the pastdecade.Multiple studies have elucidated that abnormalities in TLR signaling play apivotal role in the pathogenesis and exacerbation of SLE. Recently, the involvementof TLR-7 in the etiopathogenesis of SLE has gained significance. Since TLR7-signaling strongly induces the production of interferon alpha, which is able toenhance innate and adaptive immune response, we applied topically imiquimod toC57BL/6 mice over an 8-week period and after that analyze different parametersindicative of lupus disease induction. Anti-DNA and anti- histone antibodies weretested by ELISA and splenic lymphocyte populations were evaluated by flowcytometry technique. Additionally, leukocyte infiltration, histological changes andrenal functionality were evaluated.Imiquimod treated mice exhibited splenomegaly and a significant increase inspleen cellularity (p< 0.0003) when compared to vehicle control group. Analysis ofspleen T and B cell populations showed significant changes between imiquimod andvehicle treated mice. Indeed, higher levels of CD3+CD4+, CD3+CD8+ activated Tcells expressing CD69marker was observed in Imiquimod treated mice (p< 0.009).Regarding B cells, a significant increment in B220+CD69+ cell levels was observed(p<0.03). In addition, higher proportions of B220+IL-10+ regulatory B cells (p<0,0002), B220+CD11c+Tbet+ age-associated B cells (p>0,0009); and CD19+CD138+ CMHCII+ plasma cells (p> 0,005) were observed, reflecting a substantialactivation of the adaptive immune system in imiquimod treated mice. Imiquimodtreatment also induced the production of antibodies specifically associated withSLE. Indeed, elevated levels of IgG against double-stranded DNA and IgG againsthistones were detected in serum samples at 4 weeks and continued to increase at8 weeks of treatment (p<0.02). Significant changes were also observed at renallevel between vehicle and Imiquimod treated mice, with significant increments inCD45+ (p<0.002), CD3+CD4+ (p<0.003), CD3+CD8+ (p<0.003) and B220+(p<0,03) cells infiltrating the organ. In addition, higher proportions of age-associatedB cells were detected in Imiquimod treated (p<0.008). When serum urea andcreatinine levels were measured, we found a statistically significant increment inImiquimod treated mice suggesting the onset of renal damage.Taken together our results provide a clear overview of the immunologicalrepercussions of the chronic TLR-7 activation and not only validates a murine modelof SLE induced bya TLR-7 agonist but also underscores the immunologicaldisturbances and the onset of renal injury in C57BL/6 mice. This research broadensour understanding of TLR-7's role in SLE and paves the way for future studies.