Background/Purpose: Systemic lupus erythematosus (SLE) is a systemic autoimmune disorder characterized by periods of heightened disease activity. Disease flares significantly affect quality of life and lead to organ damage that accrues over years of waxing and waning disease. African American SLE patients have more severe disease presentation, which is likely a result of differences in immune cell subsets and activation states.

Methods:  Peripheral whole blood samples of 10 African American healthy controls and 12 SLE patients with either high (SLEDAI≥4) or low (SLEDAI<4) disease activity were stimulated with T-cell receptor (TCR), B-cell receptor (BCR), and Toll-like receptor (TLR) ligands for either 4 minutes (TLR and BCR) or 30 minutes (TCR) for phospho-protein analysis, and 24 hours for cytokine analysis of cell culture supernatants. Whole blood phenotyping and phospho-protein analysis were assessed by mass cytometry using 24 cell surface markers and 10 intracellular proteins and analyzed by hand gating and viSNE in Cytobank. Plasma cytokine and soluble mediator concentrations of stimulated cell culture supernatants were determined by 37-plex assay and by ELISA. Spotfire (version 6.0.1) and GraphPad Prism 5.04 for Windows (GraphPad Software, San Diego, CA) was used for analysis and Mann-Whitney test was used to compare non-normally distributed data. All SLE patients meet ACR classification criteria.

Results:  African American lupus patients with high disease activity had significantly elevated CD24+ granulocytes (p=0.0173), which negatively associated with IL-8 plasma levels (p<0.05) and positively associated with MCP-1 (p<0.05) compared to SLE-low disease activity patients. Granulocytes also exhibited a heightened response to TLR9 (p=0.0062), TLR4 (p=0.0446), and TLR3 (p=0.0061) stimulation with higher expression of pSTAT5 and pPLCγ2. Further, transitional B cell frequencies (p=0.0317) were also elevated in SLE-high patients versus SLE-low disease activity patients, which correlated with higher levels of Th2 plasma cytokines. Following stimulation with BCR and TLR3 stimulation, SLE-high patient B cells (p<0.05) and monocytes (p<0.04) had decreased pCREB levels, indicative of activation. Dendritic cells had decreased pSTAT1 (p=0.0446) and pSTAT5 (p=0.0106) signaling in response to BCR stimulation and decreased pSTAT3 (p=0.0427) signaling in response to TLR7/8 stimulation in SLE-high patients compared to SLE-low disease activity patients.

Conclusion:  Our results suggest that SLE-high disease activity patients have a favorable environment for granulocyte apoptosis that may work in activating other innate and adaptive subsets to drive disease flare. Further, African American SLE-high disease activity patients are more susceptible to an exaggerated TLR response. Decreased pSTAT1 signaling in dendritic cells of SLE-high disease activity patients could indicate already activated IFN pathways during periods of elevated disease activity.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/whole-blood-phenotyping-and-innate-and-adaptive-stimulation-reveal-unique-differences-in-granulocytes-and-innate-pathways-of-african-american-sle-patients-with-variable-disease-activity/