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Darren J Lee, Andrew W Taylor, Rebekah deCosier; Induction of Tregs in Uveitis Patients Through the MC5r-A2Ar Pathway. Invest. Ophthalmol. Vis. Sci. 2016;57(12):509.
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© ARVO (1962-2015); The Authors (2016-present)
Resolution of experimental autoimmune uveitis is marked by regulatory immunity in the spleen that requires the melanocortin 5 receptor (MC5r) on the APC and the adenosine 2A receptor (A2Ar) on the Tregs. Because this antigen-specific regulatory immunity provides resistance to EAU in mice, the potential to activate this pathway in PBMC from human uveitis patients was assessed.
PBMC from healthy volunteers and uveitis patients were collected. Uveitis patients were divided into two groups based on their uveitis status. Active uveitis patients (UA) had uveitis at the time of collection or within 12 months and patients with no uveitis more than 12 months (US) from the time of collection. MC5r and A2Ar expression was assessed on PBMCs by flow cytometry. PBMCs were also cultured for 48 hours with α-Melanocyte Stimulating Hormone (α-MSH) to stimulate MC5r or CGS21680 (CGS), an A2Ar agonist. Monocytes were stained with CD14, CD16, and the ectoenzyme, CD39. T cells were stained for PD-1, PD-L1, and FoxP3 following antigen specific activation with tetanus toxin (TT).
PBMC from US (n=11) and UA (n=21) patients and healthy volunteers (n=9) had similar MC5r and A2Ar expression between healthy volunteers and uveitis patients. MC5r and A2Ar expression did not change with age, type of therapy, or location of uveitis. Uveitis patients (n=5) showed more CD14+CD16- and CD14-CD16hi cells compared to healthy controls (n=2). Treatment of PBMCs with α-MSH did not change CD39 on either monocyte subset, but CGS increased CD39 expression by 7-fold in 1 of 3 uveitis patients. All CD4+CD25+ T cells were PD-L1+ and more were observed in healthy compared to patients, but was not statistically significant. These T cells from healthy volunteers (n=3) showed no change in FoxP3 expression when activated with TT and CGS. However, roughly 30% of uveitis patients from the UA (n=9) or US (n=11) groups showed an increase of 50% or more when activated with TT and CGS. PD-1 up-regulation only occurred in 20% of the US group but not in the UA group.
These results showed that stimulation of A2Ar induced Tregs and suppressive activity in monocytes in a subset of uveitis patients. Importantly, this treatment has the potential to be effective in both UA and US patient groups. This study suggests a potential treatment for uveitis through the induction of Tregs through A2Ar stimulation.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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