INTRACYTOPLASMIC TOLL- LIKE RECEPTORS (TLR) 7, 9 AND MYD88 IN PERIPHERICAL B CELL SUBSETS AS A PREDICTOR OF RENAL RESPONSE IN PATIENTS WITH LUPUS NEPHRITIS

PV134 / #630 Poster Topic: AS16 - Lupus Nephritis-Pathogenesis Background/Purpose A gain of-function mutation within TLR7 was identified in a SLE murine model and increased the survival of B lymphocytes, age associated B cells (ABCs), extrafollicular B lymphocytes and autoantibodies production, mediated by MyD88. The aim of this study is to analyze the role of TLR7, 9 and MyD88 expression in diverse B cell subsets as renal response predictors in patients with lupus nephritis. Methods We included SLE patients who fulfilled the ACR/EULAR 2019 classification criteria and active proliferative LN (Class III or IV +/- V). A blood sample was taken at baseline and 6 months after induction treatment. Treatment with anti-CD20 drugs or IVIg were excluded. The outcome was the renal response. We measured the expression of TLR7, 9 and MyD88 in the B cell subsets: ABCs [CD19 pos CD21 neg/lo CD11c hi Tbet pos ], antibody-secreting cells (ASC) [CD19 pos CD27 hi CD38 hi ], classic memory cells (CMC) [CD19 pos CD27 pos IgD pos/neg ], double negative cells (DNC) [CD27 neg IgD neg ], naïve cells (NC), non-classic memory cells (NCMC) [CD27 neg ] and transitional cells (TrC) [CD21 neg/lo ]) from a peripheral blood sample, using a BD LSR Fortessa flow cytometer and FlowJo software. We quantified the absolute numbers and percentage of TLR7, TLR9, and MyD88, alongside determining the mean fluorescence intensity (MFI). Spearman correlation coefficient was used with quantitative variables. Wilcoxon signed-rank test was used to analyze variables before and after treatment. A logistic regression was used to address association between TLRs and MyD88 expression and renal response. Results 66% of 30 patients reached renal response. These, presented a lower expression of TLR7 in NC (MFI, 573 (498-792) vs 759 (544-873), p<0.05) and expansion of TLR9+ NCMC (1.4% (0.7-2.5) vs 0.3% (0.3-0.4), p<0.05) (Table 1). At follow-up, we observed an expansion of TLR9+ B cells (8.1% (2.6-15) vs 0.5% (0.2-0.6), p<0.05); TLR9+ TrC (MFI, 747 (537-767) vs 0 ((0.0-0.0), p<0.05); TLR7+ TrC (23% (11.1-44.5) vs 0 %(0.0-0.2), p<0.05); TLR7+ NC (27.4 %(7.9-63) vs 0.3 %(0.0-0.4); TLR9+ NCMC (MFI, 1128 (1006-1135) vs 0 (0.0-0.0), p<0.05); classical TLR9+ B cells (1.9 (1.1-3.2) vs 0.07 (0.02-0.09), p<0.05), and a decreased TLR9+ ABCs (0.8 % (0.4-24.4) vs 13% (2.4-67), p<0.05) (Table 2, Figure 2). Table 1. Comparison of B cells at baseline in patients who reached renal response and those who did not. Table 2: B cells at the end of follow-up in patients who reached renal response and those who did not. Figure 1: Paired median analysis with time as an aleatory variable, in patients with and without renal response. Conclusions Our data suggest that renal response is associated with enhanced TLR9 expression in the effector humoral compartment, which might be implicated in the mechanisms of renal damage in lupus nephritis.