Background/Purpose

GM-CSF has been implicated in rheumatoid arthritis (RA) pathogenesis and is being investigated as a novel therapeutic target. B cells secreting GM-CSF have been recently reported to participate in innate immune responses in animal models. The aim of our study was to determine the expression of GM-CSF secreting peripheral B cells in RA patients.

Methods

23 patients with RA (fulfilling the 2010 ACR/EULAR RA Classification Criteria), 11 disease controls (psoriatic arthritis n=4, osteoarthritis n=3, ANCA-associated vasculitides n=2, Sjögren’s syndrome n = 1, giant cell aortitis n=1) and 10 healthy controls were included in the study. Peripheral blood mononuclear cells (PBMC) were stimulated overnight with Phorbol Myristate Acetate (PMA) and ionomycin in the presence of Brefeldin. Cells were then stained with specific antibodies against surface CD19 and intracellular GM-CSF (BioLegend). Positive cells were quantified by flow cytometry (Partec) and compared between the different groups.

Results

23 RA patients with moderate to high disease activity not receiving anti-rheumatic drugs (females/males=19/4, DAS28-CRP=5.53 ± 0.84, median disease duration=14 months, RF and/or anti-CCP+=52%) were studied. The % of peripheral B cells (CD19+) was similar between the RA and the 2 control groups (6.9 ± 3.9% vs. 6.3 ± 3.5% vs.8.4 ± 1.9%, p=NS). We detected an expanded population of peripheral CD19GM-CSF + cells in RA patients (4.4 ± 2.6%) compared to disease (1.1 ± 1.5%, p=0.0002) and healthy (0.2 ± 0.2%, p=0.00000002) controls while there was no difference between disease and healthy controls (p=0.512). Similarly, we did not observe any difference between seropositive (RF and/or anti-CCP+, 4 ± 2.6%) and seronegative (4.8 ± 2.5%, p=0.347) patients. GM-CSF+ B cell expression did not correlate with RA disease activity measured by DAS28 (p=0.926, Spearman correlation).

Conclusion

Our study shows for the first time an expanded population of peripheral B cells expressing GM-CSF among patients with active RA compared to patients with other inflammatory or non-inflammatory rheumatic diseases and healthy controls. The functional significance of this cell population remains to be determined.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/patients-with-active-rheumatoid-arthritis-display-an-expanded-population-of-gm-csf-expressing-peripheral-b-cells/