Session Type: Abstract Submissions (ACR)
SLE involves complex interactions between the innate and adaptive immune systems. Monocytes are increasingly recognised to play a key role in the dysregulated immune response seen in SLE whilst more recently BLyS has been demonstrated to play a key role in the pathogenesis of SLE. Despite the fact that monocytes are one of the key producers of BLyS, the effect of BLyS on monocyte function in health and SLE is poorly understood. The aim of this study was to investigate the effect of BLyS on monocyte signalling and activation in healthy controls and to determine its role in the pathogenesis of SLE.
Signalling pathways following BLyS stimulation were investigated by Western Blotting in monocytes from healthy controls and SLE patients. qPCR was utilised to investigate pro-inflammatory gene expression. Monocyte supernatant and serum levels of proinflammatory cytokines were measured by ELISA. CD 14+ monocyte activation was assessed by Flow Cytometry. Differences between groups were examined using the Mann Whitney.
Following stimulation with BLyS an increase in phosphorylated levels of STAT1, AKT, p42/44 MAPK and p38 MAPK was observed in healthy controls indicating BLyS signals via a number of pathways in monocytes. A corresponding decrease in total IkB levels was observed. Strikingly SLE patients exhibited significantly enhanced responses to BLyS stimulation compared to controls for the phospho-p42/44 MAPK, AKT and STAT pathways.
qPCR analysis revealed significant increases in BLyS, IL-6 and IFN-γ gene expression in SLE patients following stimulation, a finding that was not replicated in controls. Subsequent ELISA confirmed significantly enhanced IL-6 production in the supernatant of SLE patient monocytes compared to controls following BLyS stimulation. Furthermore the SLE patients exhibited significantly higher levels of IL-6 in their serum.
With regard to BLyS receptors, SLE patient monocytes demonstrated a significant upregulation of TACI expression following stimulation. Increased levels of BAFF-R were also seen in both patients and controls following stimulation.
With respect to monocyte activation SLE patients expressed significantly more CD80, CD86 and HLA-DR in the resting state compared to healthy controls. Despite this baseline hyperactivated state, BLyS stimulation resulted in significant increases in CD80, CD86 and MHC Class II in SLE patients. In contrast the healthy control volunteers failed to significantly upregulate any of the surface markers following BLyS stimulation indicating that SLE patients monocytes are more responsive to the effects of BLyS. Interestingly SLE patients with evidence of immunological activity (dsDNA +ve/Low C3/C4) exhibited enhanced HLA-DR and CD86 expression following BLyS stimulation compared to patients without evidence of such activity.
Finally co-culture of BLyS treated monocytes with T lymphocytes resulted in enhanced expression of the T cell activation marker CD69 on both CD8 and CD4+ T Cells, a finding that was significant in SLE patients.
BLyS promotes dysregulation of monocyte activation and signalling pathways in SLE with consequential excess production of pro-inflammatory cytokines and enhanced T cell activation.
E. M. McCarthy,
J. Ní Gabhann,
L. O’ Neill,
E. S. Molloy,
P. G. O’Connell,
G. M. Kearns,
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/b-lymphocyte-stimulator-blys-promotes-dysregulated-monocyte-function-in-systemic-lupus-erythematosussle/