CD11c+ Expression Associates with IFN-? Responsiveness in Human B cells with clinical implications for SLE

Type I interferon (IFN), namely IFN- a, and B cell aberrations are long recognized in systemic lupus erythematosus (SLE) pathogenesis. Type I IFN receptor blockade has undergone clinical trials in SLE with varying degrees of success. Type III IFN (IFN-?) produce a gene signature currently indistinguishable from that of type I in responsive cell types. IFN-? are not blocked by type I IFN receptor blockade as they utilize a unique receptor (IFNLR1). Type III IFN are appreciated to have an important role in viral infection at epithelial barriers where IFNLR1 is strongly expressed. The effects of IFN-? on immune cells remain understudied and are different between human and murine models. We have previously shown that human B cells can transcribe type I IFN genes after IFN-? treatment including those associated with SLE. We have found that IFN-? is detected in the serum of human SLE patients and correlates with IgD- CD27- CD21- CD24- (DN2) B cells, a compartment which contains CD11c+ age/autoimmunity B cells (ABC). ABC are a target of interest as recent studies suggest they are poised for plasma cell differentiation and enriched in autoreactivity and thus have the potential to contribute to SLE pathogenesis. Results: Naïve and DN cells display a prominent type I IFN gene expression profile in SLE. Transcript for type I, type II, and type III IFN receptors (IFNAR1, IFNAR2, IFNGR1, IFNGR2, IFNLR1, and IL10RB) are detected in HD and SLE B cells. CD11c+ CD21- frequency increased in DN compared to naïve B cells for SLE and HD (both p< 0.001). The mean and range of CD11c+ CD21- frequency was higher in SLE DN (30.7± 9.5%, mean±SEM; range 4.8-74.7%) compared to HD DN (7.6%±1.0%,3.6-9.4%). Increased IFNLR1 transcript correlated with CD11c+ CD21- B cell expansion (r2=0.922, p<0.0001). Increased pSTAT1 after IFN-a2 treatment is found in monocytes, T cells, and B cells but only in the B cells after IFN-?1 treatment. Naïve, DN, switched, and unswitched memory HD B cells are responsive to type I and type III IFN, but demonstrated a higher pSTAT1 fold change with type I IFN treatment compared to type III IFN. In all B cell subsets, CD11c+ cells had a higher pSTAT1 fold change after IFN-?1 stimulation than did CD11c- B cells. In HD with well-defined populations of CD11c+ CD21- DN cells, pSTAT1 fold change for IFN-? approached that of IFN-a2. Conclusions: All human B cell subsets defined by CD27 and IgD respond to IFN-a and IFN-?, but those expressing CD11c+ have increased responsiveness to IFN-?. CD11c+ cells expand in SLE and associate with autoreactive plasma cell development. Thus, the role of IFN-? may take on increased clinical significance in the setting type I IFN receptor blockade. These results suggest IFN-? is an underappreciated driver of the IFN signature and B cell aberrations in SLE. Overall design: Patients meeting 1997 ACR systemic lupus erythematosus classification criteria (n = 8) and healthy donors (HD, n = 5) had blood drawn under IRB-approved protocol. The transcriptome of sorted IgD+ CD27- naïve and IgD- CD27- (DN) B cells was measured by bulk RNA sequencing for differential expression and gene set enrichment analysis. Cell phenotype and STAT1 phosphorylation (pSTAT1) in IFN-a2 and IFN-?1 treated PBMC was measured by flow cytometry (n =10).