Session Title: Cytokines, Mediators, and Gene Regulation
Session Type: Abstract Submissions (ACR)
Background/Purpose: Rheumatoid arthritis (RA) is the most common inflammatory arthritis. B and T lymphocytes play a central role in the pathophysiology of RA. RasGRP is a member of the CDC25 family of Ras guanyl nucleotide exchange factors. RasGRP1 is expressed in T and B cells whereas RasGRP3 is only expressed in B cells. In previous studies, we have shown that RasGRP3expression level significantly decreased in Peripheral blood mononuclear cells (PBMC) from RA patients responders to adalimumab after 3 months, leading to the question of TNFα involvement in pathways including RasGRP1 and RasGRP3. Objectives : To study TNFα effect on RasGRP1 and RasGRP3 expression levels in vitro.
Methods: We measured by qRT-PCR, RasGRP1 and RasGRP3 expression levels, i) in PBMC from 3 healthy controls (HC), ii) in negative selected B and T cells from PBMC isolated from 3 buffy coat. In each condition, cells were cultured with or without BCR or TCR stimulation for 4 days and TNFα was added for 24 or 48 hours. Immunofluorescence staining was performed to check the cell purity and B and T cells stimulation by flow cytometry. Moreover, IL-2 production was measured by ELISA in T-cells before and after TNFα stimulation. In addition, TNFα effects on cell proliferation were evaluated by [3H] thymidine incorporation by the B and T cells.
Results: In B cells, TNFα induced an increase of RasGRP1 (p<0.001) and RasGRP3 (p<0.001) expression levels in absence of BCR stimulation. In the same way, in T cells, TNFα induced an increase of RasGRP1 (p<0.001) and RasGRP3 (p<0.001) expression levels in absence of TCR stimulation. Furthermore, TNFα induced a significantly increased of IL-2 production (p<0.05) in unstimulated T-cells. However, TNFα have no effects on B and T cells proliferation
Conclusion: This study suggests the RasGRP1 and RasGRP3 regulation by TNFα, independently of B and T cells stimulation. The increasing of RasGRP3 and RasGRP1 in B and T cells specifically via TNFα binding on its receptors could promote the activation and proliferation of B and T cells using another signaling pathway than BCR and TCR. This second pathway could explain the maintenance of B and T cells activation by an independent antigen pathway.
M. L. Potier,
X. Le Loët,
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/tnf%ce%b1-influences-rasgrp1-and-rasgrp3-expression-levels-in-pbmc-b-and-t-cells/