Abstract
Purpose :
To measure the importance of Th1 and Th17 responses in the pathogenesis of chronic post-infectious uveitis in the primed mycobacterial uveitis (PMU) model in comparison with the spontaneous resolving unprimed mycobacterial uveitis (UMU) model.
Methods :
PMU and UMU were induced in C57BL/6J mice. Inflammation was scored using OCT. Ocular Th1(CD3+, CD4+, Tbet+), Th17 (CD3+, CD4+, RORγt), and Treg (CD3+, CD4+, CD25+, Foxp3+) cells were quantified and expression of IL-17A and IFN-γ measured by flow cytometry on days 7, 28, and 56. Vitreous and serum cytokines were measured by Multiplex ELISAs on D7 and D28, and the ocular/serum concentration ratio determined.
Results :
Consistent with previous results, PMU eyes were significantly more inflamed when compared to UMU eyes. Detailed flow analysis began on D7 when uveitis in PMU eyes continued but UMU eyes were quiet. On D7, the number of CD4+ T cells in PMU eyes (37,523±14,870 cells/eye) was significantly higher than in UMU eyes (359±275 cells/eye, p=0.006) and the majority demonstrated a Th17 phenotype (#20,964±6,849 cells/eye, 56% of CD4). In contrast, in UMU eyes the majority consisted of an undefined Tbet-, RORγt-, Foxp3- population (#137±35 cells/eye; 48% of CD4) with few Th17+ cells (#121±113 cells/eye; 30%). At later time points, the total number of ocular CD4+ T cells in PMU eyes declined but remained Th17 dominant: D28 (#3,076±565 cells/eye; 48%) and D56 (#1,801±953 cells/eye, 50%). Th1 cells constituted a larger proportion of the ocular CD4+ T cells over time in PMU, but remained significantly lower in both number and proportion when compared to Th17 populations (D28 #1,441±415 cells/eye, 22%, p=0.03; D56 #712±575 cells/eye, 20%, p=0.01). PMU vitreous demonstrated significantly higher concentrations of IL-17A than serum on D7 (398±81 pg/ml, p<0.001) and on D28 (56±16 pg/ml, p=0.05) consistent with a local Th17 response. Other chemokines associated with chronic inflammation including CXCL9, CXCL10, CCL2, CCL3, CCL4, and IFN-γ demonstrated high ocular/serum concentration ratios on D7 and D28 while local concentrations of acute cytokines such as IL-6 declined.
Conclusions :
Chronic post-infectious uveitis in PMU is associated with a local Th17 dominant adaptive immune response. Elevated concentrations of vitreous CXCL9, CXCL10, CCL2, CCL3, CCL4, IFN-γ, and IL-17A suggest these are important mediators of chronic inflammation in the eye.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.