Background/Purpose:  

Systemic Lupus Erythematosus (SLE) is a multi-system rheumatic disease with widely differing clinical manifestations and outcomes. Treatment is generally immunosuppressive, with no available biomarkers to inform therapeutic selection for a given patient or disease manifestation. Profiling the immune signaling pathways in PBMCs from patients with active SLE and healthy donors (HD) enables improved understanding of pathobiology and provides a basis for rational treatment decisions.

Methods:

Single Cell Network Profiling (SCNP) is a multiparametric flow cytometry based technology that enables simultaneous quantitative analysis of signaling networks in multiple immune cell subsets. PBMC from 60 SLE patients meeting ACR (2007) criteria with SELENA-SLEDAI scores ≥6 were profiled by SCNP and compared to PBMC from 59 age, gender and race matched HD in the presence and absence of modulators of immune function (11 cytokines; 5 toll-like receptor (TLR) modulators and IL-1β; B cell-specific modulators CD40L and Anti-IgD, and PMA), across B (defined by IgD and CD27) and T (CD4/CD45RA) cell subsets, monocytes, and dendritic (HLA-DR, CD11b, CD123) cells, and evaluated through induced p-STATs, MAPK, PI3K and NFkB pathway readouts. 

Results:

SLE vs HD: SLE PBMC overall had a broader signaling range than HD, with median modulated signaling in B and T cells lower in SLE. Exceptions include IFNγ->p-STAT1 in B cells and CD45RA+CD4+ T cells, IL-2->p-STAT5 in CD45RA+CD4+ T cells, IL-4->p-STAT6 in T cell subsets, and IL-10->p-STAT1, -3 in T cell subsets. Modulation of p-STAT1 by IFNγ, IL-10 and IL-27, and IL-6->p-STAT3 was increased in SLE monocytes. TLR->p-ERK, but not NFkB signaling was increased in monocytes. SLE mDCs showed elevated TLR7/8 induced IkB degradation. Unmodulated levels of intracellular readouts and PMA induced signaling were similar between SLE and HD, suggesting that 1. Signaling differences are not the result of elevated unmodulated levels of signaling and 2. Overall signaling capacity is not compromised in SLE.

SLE donor subgroups: Distinct signaling profiles were identified based upon multivariate analysis of signaling within the SLE population. Not only was signaling quantitatively more broadly distributed in SLE vs HD, distinct subgroups were also observed (Table 1). Associations of dysfunctional signaling with donor demographics, including belimumab treatment will be presented.

Table 1. Subgroups of SLE patients based on modulated signaling outside the range for HD.

Conclusion:

These SCNP data identify both modulator-specific, disease-associated dysfunctional signaling and SLE donor subgroups based upon cell subset specific immune signaling capacity. Ongoing analyses will inform on the clinical relevance of these observations to enable functional refinement of the spectrum of SLE and identification of novel targets for therapeutic intervention.