Single cell analysis revealed distinct B-cell subpopulations that produce or respond to type I interferon in SLE

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Abstract We previously showed that B-cell endogenous expression of interferon beta (IFNβ) is associated with the development of autoreactive B cells in BXD2 autoimmune mice. As among all type I IFNs, IFNβ exhibits the highest affinity to IFNAR1 and IFNAR2 and IFNβ also can stimulate IFNαs, there is a pressing need for a better understanding of the source and responses of IFNβ in systemic lupus erythematosus (SLE). Flow cytometry and super-resolution imaging analysis showed increased expression of IFNβ in B cells obtained from PBMCs of SLE patients compared to healthy controls. The importance of SLE B-cell endogenous IFNβ in regulating TLR7-mediated responses was identified when CL264 (a TLR7 ligand) plus anti-Ig-induced CD69 and survival of purified B cells were significantly and equivalently suppressed by an anti-IFNβ or an anti-IFNAR1 blocking antibody. We next carried out single cell qRT-PCR analysis to determine if B-cell endogenous IFNβ acts in an autocrine or paracrine manner to modulate IFN stimulated genes (ISGs). Hierarchical analysis revealed three prominent and consistent clusters, consisting of an IFNB+ cluster, an ISG+ cluster, and an IFNA+ cluster in naïve B cells isolated from 3 SLE patients. Cells within the IFNB+ cluster expressed higher levels of IFNB, IFNA1, IFNA8, and TLR7. Cells within the ISG+ cluster expressed higher levels of IFNAR1, IFNAR2, BAFFR, MX1, RIG1 and TLR9. Cells within the IFNA+ cluster expressed higher levels of IFNA4, IFNA10, IFNA14, IFNA16, IFNA17, and TLR3. Together, the results reveal (1) B cells as an important source of IFNβ in modulating TLR7 responses in SLE; (2) a well-orchestrated program in modulating IFNβ donor versus responder B cells; and (3) some patients may benefit from specific targeting of IFNβ.