IL-4 acts through aryl hydrocarbon receptor to antagonize TLR7 induced double negative 2 B cells in lupus

Abstract We recently showed that in systemic lupus erythematosus (SLE), IL-4R signaling is a powerful antagonist that can effectively suppress the development of activated naïve (aNAV) and CD11c +T-bet +IgD −CD27 −double negative 2 (DN2) B cells promoted by both type I and type II IFNs. In the present study, we used the BXD2 mouse model of lupus to determine the mechanism of IL-4 in suppressing the development of DN2 B cells in vivo. Administration of IL-4 significantly inhibited the development of anti-Smith, anti-DNA, and anti-histone autoantibodies induced by TLR7 agonist R848 in BXD2 mice. This was associated with a decreased percentages of CD11c +T-bet +IgD −B cells. Feature-barcoding single cell RNA-sequencing analysis showed that IL-4 modulated B cell development at the transitional stage 2 (T2) and skewed naïve B cells to develop into the CD23 +CD21 −follicular B cells. IL-4 induced the gene encoding interleukin-4-induced1 (IL4i1), an enzyme that metabolizes aromatic amino acids and this was associated with the upregulation of aryl hydrocarbon receptor (AhR) and downstream genes. Metabolomics analysis revealed IL-4 induced AhR agonistic metabolites in B cells including kynurenine (Kyn), indole-3-acetic acid, and indole-3-lactic acid. In the absence of IL-4, Kyn and a potent AhR agonist, formylindolo[3,2-b]carbazole (FICZ), significantly suppressed TLR7 plus IFNβ-induced DN2 B-cell development in vitro. Our results suggest that IL-4 acts through the IL4i1-AhR pathway to inhibit B-cell regulatory response to TLR7 and type I IFN. Identification of small molecular metabolites that act directly in B cells to induce homeostasis may lead to development of orally dosed metabolome modulating therapeutics efficacious in the treatment of SLE. This study was supported by grants from VA Merit Review grant (I01BX004049), NIH grants R01 AI134023, and Lupus Research Alliance Distinguished Innovator Award to J.D.M, the LRA Target Identification in Lupus Award to H-C.H., and the P30-AR-048311.