W126 - Intracytoplasmic TLRs and MyD88 in B Cells Subsets as Key Elements of Lupus Nephritis

Abstract Text: We carried a cross-sectional study with 28 lupus nephritis (LN) and 26 non-renal active lupus patients, from which we isolated PBMCs to mark them for flow cytometry analysis of TLR7, 9 and MyD88 expression in total B cells (CD19+), age-associated cells (CD21- CD11c+ T-bet+), classical memory (CD27+), plasmablasts (CD27hi CD38hi), transitional (CD27- CD24hi CD38hi), non-classical memory (CD27- CD24+ CD38-/lo), naïve (CD27- CD24- IgD+) and double negative (DN, CD24+ CD27- IgD-) B cells. Additionally, we measured 29 serum cytokine levels in a multiplex assay. After assessment of confounding variables with the G-test, we evaluated the relation of relative (%) and absolute (cells/mm3) number of cells expressing TLR7, TLR9 and MyD88, and their MFI with the development of LN with the Wald test. Finally, we selected a linear mixed model for renal activity with the highest relative quality, according to the Akaike information criterion.
In order to avoid erroneous attribution of the results to treatment effects, analysis was delimited to subjects not receiving mycophenolic acid since a higher proportion of LN patients were under this treatment (60.7%, n=17 vs 30.8%, n=8, p=0.02). Higher MyD88 expression in transitional, naïve, DN, classical and non-classical B cells related to renal activity. As well as increased TLR7 in naïve, non-classical and DN B cells; and TLR9 in transitional cells. Eoxatin was the only cytokine significantly related to LN. Our final predictive model for LN includes TLR9 MFI in transitional B cells (OR 1.003, CI95% 1.001-1.01 p= 0.013) and eotaxin serum levels (OR 1.01 CI95% 1.003-1.03).