Background/Purpose: Systemic lupus erythematous (SLE) is a heterogenous autoimmune disorder characterized by pathogenic antinuclear antibodies. An interferon (IFN) gene signature and B cell aberrations are found in subsets of SLE patients. Type I IFN is involved in immune cell activation, correlates with disease activity, and promotes plasma cell (PC) development. Anifrolumab is a monoclonal type I IFN receptor neutralizing antibody approved for SLE treatment. Anifrolumab reduces PC numbers differentiated from B cells in vitro.CD11c+ T-Bet+ autoimmune-associated B cells (ABC) are expanded in SLE and thought to be precursors to autoreactive antibody-producing PCs. We hypothesized that B cell IFN responsiveness is determined by phenotype and past in vivo IFN exposure. Here, we characterized the IFN response of IgD- CD27- double negative (DN) B cells, a subset enriched in CD11c+ T-Bet+ ABCs in SLE.

Methods: We screened our biorepository of SLE peripheral blood mononuclear cells (PBMC) for IFI27 expression, an IFN stimulated gene, by quantitative RT-qPCR. Serum IFN-α levels were measured by ELISA. Age, sex, and race matched IFI27-low and high SLE PBMCs were stimulated with IFN-α2 or IFN-λ1 then immunostained for flow cytometry (n=9 pairs plus n=5 matched healthy donor, HD). STAT1 phosphorylation after IFN stimulation was measured by median fluorescent intensity. We measured IFNLR1 expression (type III IFN receptor subunit) in HD B cells by RT-qPCR after TLR and IFN stimulation. Flow cytometry immunophenotyping of PBMC from SLE patients starting anifrolumab prior to first infusion and after second infusion was used to identify DN1 (CD11c- T-Bet- IgD- CD27-) and DN2 (CD11c+ T-Bet+ IgD- CD27-) B cells.

Results: SLE PBMC with high IFI27 had significantly higher level serum IFN-α compared to PBMC from SLE with low IFI27 or HD. Baseline pSTAT1 was not statistically different between low versus high SLE IFI27 donors for ABC/DN2 or DN1.However, ABC/DN2 had higher baseline pSTAT1 when compared to DN1 from the same donor in all groups (HD p=0.02, IFI27 low 0.0001, IFI27 high,0.0008; Wilcoxon matched pairs signed rank test with FDR). DN1 responsiveness to IFN-α was markedly reduced when cells were derived from a high IFI27 patient (p=0.001 for Δstim-unstim pSTAT1) while ABC/DN2 response was unchanged. Despite higher baseline pSTAT1, Δstim-unstim pSTAT1 was higher (p=0.001) after IFN-λ1 stimulation when ABC/DN2 came from a high IFI27 donor. IFN-α2, IFN-λ1, and IFN-γ did not change total B cell IFNLR1 expression. However, TLR7 agonist R848 was able to increase IFNLR1. One month of anifrolumab therapy did not alter percentages of ABC/DN2 in our preliminary phenotyping analyses for ABC/DN2.

Conclusion: Our data demonstrate that type I and type III IFN have differential effects on B cells subsets in both SLE and HD. When cells are derived high IFN environments in SLE, responsiveness of ABC/DN2 to type III IFN is increased while DN1 remain minimally responsive to type III IFN and have reduced type I responses as compared to DN B cells derived from low IFN patients. The role of type III IFN in the setting of type I IFN blockade such as anifrolumab requires further exploration given its potential to stimulate ABC/DN2, a B cell subset target of interest.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/systemic-lupus-erythematosus-b-lymphocyte-responsiveness-to-type-i-and-type-iii-interferon-is-determined-by-donor-ifn-status-and-b-cell-phenotype/