Session Type: Abstract Submissions (ACR)
Monocytes are increasingly recognised to play a key role in the pathogenesis of SLE. Different subpopulations of monocytes contribute to the disease through dysregulated pro and anti-inflammatory responses. B Lymphocyte Stimulator(BLyS) has been shown to promote disease activity in SLE however its effect on monocyte subpopulation differentiation has not previously been reported. This study sought to investigate the effect of BLyS on monocyte subpopulations in healthy controls and SLE patients.
25 Patients with matched controls were recruited. CD 14+ monocyte subpopulations were analysed by Flow Cytometry using the following markers: M1 CD86+ HLA-DR+ ; M2a CD163+ CD206+ ; M2b CD86+ HLA-DR+ CD163+. qPCR was utilised to investigate gene expression for the subsets markers as follows: M1 CXCL10; M2a CCL17; M2b CCL1 . Serum levels of cytokines were measured by ELISA. Differences between groups were examined using the Mann Whitney.
Following stimulation with BLyS a significant increase in the pro-inflammatory M1 and anti-inflammatory M2a monocyte subpopulations was observed in healthy controls and SLE patients with a corresponding decrease in M2b levels.
Interestingly SLE patients demonstrated a trend toward increased M1 levels in both the resting state and following BLyS stimulation in comparison to controls. In keeping with this SLE patient M1 monocytes exhibited significantly enhanced HLA-DR MFI expression in the resting state and following stimulation compared to controls. Furthermore a significant increase in CD86 MFI was observed following BLyS stimulation in patients, a result not replicated in controls. No differences were observed between patients and controls with regard to the M2b subpopulation.
In keeping with the literature SLE patients exhibited significantly reduced basal M2a levels. Surprisingly however, following BLyS stimulation an increased percentage of M2a monocytes was observed in patients compared to healthy controls(12.7% v 8.3%) such that the fold change from baseline in M2a monocytes between patients and controls following BLyS stimulation was significantly different (3.6 v 1.4,p= 0.0096).
In support of this qPCR confirmed a significant increase in the M2a-associated gene CCL 17 in SLE patients following stimulation, a result not replicated in controls. No absolute differences were observed in expression for the M1-associated gene(CXCL10) and M2b-associated gene(CCL1).
Strikingly BLyS stimulation significantly increased the M1 subpopulation in SLE patients with evidence of immunological activity(dsDNA+ve), an observation not replicated in dsDNA –ve patients.
Finally determination of M1 and M2 subset associated cytokines by ELISA confirmed significantly enhanced levels of both CXCL10(M1) and CCL17(M2a) in the serum of SLE patients with a strong correlation seen between CXCL10 and both dsDNA levels and disease activity. CCL17 demonstrated modest correlation with disease activity.
Our study highlights a heterogenous response to BLyS stimulation in both healthy control and SLE patient monocytes. SLE patient monocytes appear to have enhanced pro and anti-inflammatory responses to BLyS a finding which warrants further investigation
E. M. McCarthy,
J. Ní Gabhann,
P. G. O’Connell,
G. M. Kearns,
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-role-of-b-lymphocyte-stimulator-in-monocyte-subpopulation-differentiation-in-sle/