Abstract
Purpose :
Experimental autoimmune uveitis (EAU) represents autoimmune uveitis in humans and is used to study mechanisms and potential therapeutics. Tristetraprolin (TTP) is an inducible, tandem zinc-finger mRNA binding protein that binds to adenylate-uridylate-rich elements (AREs) in the 3'-untranslated regions (3'UTRs) of specific mRNAs, e.g., TNF-α. Here, we examined EAU and related immune responses in knock-in tristetraprolin-mutated (TTPΔARE) mice.
Methods :
TTPΔARE mice, which overexpress TTP, were generated as described (PMID: 26831084). Wild-type (WT) C57BL/6 mice were used as controls. Heterozygous mice were generated by crossing the two lines. EAU was induced by immunization with 150μg of IRBP + 300μg of IRBP peptide 1-20. EAU progression was monitored by funduscopy and confirmed by histology. Cellular immune responses to IRBP were assessed by: (i) production of IFN-γ, IL-17, IL-6, TNF-α and IL-10 in culture by IRBP-stimulated spleen and lymph node cells, using ELISA kits and (ii) quantitation of IFN-γ, IL-17 and Foxp3-expressing cells by flow cytometry. Serum antibody against IRBP was measured by an in-house ELISA. Adoptive transfer of EAU was performed by injection of lymphocytes specific to IRBP peptide 651-670 into naïve recipients.
Results :
TTPΔARE mice failed to develop EAU. Compared to WT controls, they produced significantly lower levels of the pro-inflammatory cytokines IFN-γ, IL-17, IL-6 and TNF-α and increased levels of anti-inflammatory IL-10 and the regulatory FoxP3. TTPΔARE mice also produced lower levels of serum antibodies to IRBP, in particular of the IgG2a isotype. Heterozygous mice developed EAU and the immune responses at intermediate levels. In contrast, TTPΔARE recipients of IRBP-specific T cells developed similar disease to control WT recipients.
Conclusions :
Overexpression of TTP throughout the body in TTPΔARE mice protects them from the development of EAU and reduces their production of pro-inflammatory cytokines. TTPΔARE mice also exhibited higher levels of the anti-inflammatory cytokine IL-10 and of regulatory cells expressing FoxP3+. Heterozygous mice responded with intermediate levels of disease and immune responses. TTPΔARE mice, however, resembled their WT controls in developing adoptively transferred EAU, suggesting that the immune deficiency is due to a defect in pro-inflammatory priming of antigen-specific T cells.
This is a 2020 ARVO Annual Meeting abstract.