Background/Purpose: Regulatory T cells (Treg) are potent suppressors of immune responses and are considered a pivotal element in resolving inflammation and autoimmunity. We have previously shown that an increase in CD4 Treg numbers occurs in the peripheral blood of rheumatoid arthritis (RA) patients who have responded to adalimumab but not to the soluble TNF receptor etanercept. Most recently, we demonstrated that adalimumab expands Th17 suppressing Treg by paradoxically promoting membrane TNF–TNFRII binding in RA [1]. We hypothesized that an in vitro Treg expansion assay could predict RA patient’s clinical response to anti-TNF antibody therapy.

Methods: RA patients (all fulfilled ACR criteria) who were to begin adalimumab (n=13) were recruited and blood samples taken before (baseline), 3 and 6 months after therapy. Disease activity was assessed using DAS28 and clinical response defined as a drop in DAS28 >1.2 compared to the pre-treatment value. PBMC isolated from RA patients before adalimumab treatment were cultured for 3 day with 10µg/ml adalimumab. On day 3, flow cytomety analysed CD4 and CD8 FoxP3 expression and membrane TNF staining on CD14+ monocytes. Treg expansion was defined as an increase of 45% compared to the unstimulated value.

Results: The addition of adalimumab to PBMC from patients with active RA before adalimumab therapy resulted in a significant increase in monocyte membrane TNF expression (p= 0.0078) and the percentage of CD4 Treg (p= 0.0039) only in patients (n= 9) who then responded to adalimumab therapy as assessed at 3 months post treatment. Moreover, the percentage of CD8+FoxP3+ Treg in PBMC from patients before therapy was elevated by addition of adalimumab in vitro (p=0.0078) and in the peripheral blood of patients analysed at 3 months who responded to therapy. The percentage of CD4 and CD8 Treg expanded by adalimumab in vitro at baseline correlated with the percentage of peripheral blood Treg in patients at 3 months post adalimumab therapy.

Conclusion: CD8 as well as CD4 Treg are expanded by adalimumab in patients with RA. Collectively our data suggest that an in vitro assay based on Treg expansion could predict clinical response to anti-TNF therapy in RA if confirmed in a larger cohort. This predictive test could be of benefit not only as a potential cost saving, prevent risks associated with exposure to numerous anti-TNF agents but represents a step forward to personalised medicine.

1. Nguyen DX and Ehrenstein MR. Anti-TNF drives regulatory T cell expansion by paradoxically promoting membrane TNF-TNF-RII binding in rheumatoid arthritis. J Exp Med, 2016 June 6.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/in-vitro-expansion-of-treg-by-adaimumab-predicts-clinical-response-to-therapy-in-patients-with-rheumatoid-arthritis/