Type III interferons (IFN-lambdas(λ)) are important cytokines that inhibit viruses and modulate immune responses by acting through a unique IFN-λR1/IL-10RB heterodimeric receptor. Until now, the primary antiviral function of IFN-λs has been proposed to be at anatomical barrier sites. Here, we examine the regulation of IFN-λR1 expression and measure the downstream effects of IFN-λ3 stimulation in primary human blood immune cells, compared with lung or liver epithelial cells. IFN-λ3 directly bound and upregulated IFN-stimulated gene (ISG) expression in freshly purified human B cells and CD8 + T cells, but not monocytes, neutrophils, natural killer cells, and CD4 + T cells. Despite similar IFNLR1 transcript levels in B cells and lung epithelial cells, lung epithelial cells bound more IFN-λ3, which resulted in a 50-fold greater ISG induction when compared to B cells. The reduced response of B cells could be explained by higher expression of the soluble variant of IFN-λR1 (sIFN-λR1), which significantly reduced ISG induction when added with IFN-λ3 to peripheral blood mononuclear cells or liver epithelial cells. T-cell receptor stimulation potently, and specifically, upregulated membrane-bound IFNLR1 expression in CD4 + T cells, leading to greater antiviral gene induction, and inhibition of human immunodeficiency virus type 1 infection. Collectively, our data demonstrate IFN-λ3 directly interacts with the human adaptive immune system, unlike what has been previously shown in published mouse models, and that type III IFNs could be potentially utilized to suppress both mucosal and blood-borne viral infections.
Systemic lupus erythematosus is a chronic multi-organ autoimmune disease marked mainly by the production of anti-nuclear antibodies. Nuclear antigens become accessible to the immune system following apoptosis and defective clearance of apoptotic debris has been shown in several knockout mouse models to promote lupus. However, genetic loci associated with defective clearance are not well defined in spontaneously arising lupus models. We previously showed that introgression of the chromosome 13 interval from lupus-prone New Zealand Black (NZB) mice onto a non-autoimmune B6 genetic background (B6.NZBc13) recapitulated many of the NZB autoimmune phenotypes. Here, we show that B6.NZBc13 mice have impaired clearance of apoptotic debris by peritoneal and tingible-body macrophages and have narrowed down the chromosomal interval of this defect using subcongenic mice with truncated NZB chromosome 13 intervals. This chromosomal region (81–94 Mb) is sufficient to produce polyclonal B and T cell activation, and expansion of dendritic cells. To fully recapitulate the autoimmune phenotypes seen in B6.NZBc13 mice, at least one additional locus located in the centromeric portion of the interval is required. Thus, we have identified a novel lupus susceptibility locus on NZB chromosome 13 that is associated with impaired clearance of apoptotic debris.
Type III interferons (IFN-lambdas) are important antiviral cytokines that also modulate immune responses by acting through a unique IFN-λR1/IL-10R2 heterodimeric receptor. Conflicting data has been reported for which human cells express the IFN-λR1 subunit and directly respond to IFN-λ. Since the commercially available anti-IFN-λR1 flow cytometry antibodies we tried were suboptimal, we developed a novel method to measure IFN-λ3 binding to IFN-λR1/IL-10R2 on the surface of cells via flow cytometry. We found that Huh7.5 hepatoma cells bound IFN-λ3 to the greatest extent with the lowest Kd(app) (83.2nM), and had the corresponding highest induction of IFN stimulated genes (ISGs). Raji and Jurkat cell lines, representing B and T cells, respectively, moderately bound IFN-λ3 and had lower ISG responses. U937 cells, representing monocytes, did not bind IFN-λ3 and therefore, did not have detectable ISG induction. We confirmed that IFN-λ3 was bound to the surface of cells through imaging flow cytometry. Importantly, lentivirus shRNA knockdown of IFNLR1 in Huh7.5 cells decreased our binding signal proportionally and reduced ISG induction by up to 93%. IFN-λ3 responsiveness increased over time with maximal ISG responses seen at 24 hrs for all but one gene. We next applied our assay to human peripheral blood mononuclear cells and saw that only specific immune cell subsets bound IFN-λ3 (eg. plasmacytoid dendritic cells and B cells). These data confirm our new IFN-λ3 binding assay can be used to quantify where the IFN-λ receptor is expressed and reflects IFN-λ3 responsiveness. Knowing which cells express the IFN-λ receptor will be crucial for determining how IFN-λ3 modulates the adaptive immune response.
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