Abstract
Purpose: :
In experimental autoimmune uveitis (EAU), there is selective upregulation of A crystallins in the photoreceptors. We investigated the role of this protein on innate and adaptive immune responses and retinal damage in EAU.
Methods: :
Three groups of mice, B10.RIII, A knockout (KO), and wild type mice, were immunized with IRBP peptide. The B10.RIII mice were divided into four subgroups of six animals each; mice in each group received intravenous 10µg of A or β or γ crystallins or normal saline on alternate days from day 14 post immunization (p.i.). The eyes were enucleated on day 21 p.i. and immunohistologically graded for severity of inflammation and IRBP expression in the retina. Similarly, 24 A KO immunized mice were treated from day 1with A or saline; 12 were killed on day 7 p.i., and the remaining 12 on day 21 p.i.. Eyes enucleated on day 7 p.i. were submitted to PCR array to detect TLRs and genes in its signaling pathway, including adapters, interacting proteins, and NFkB signaling gene expression. Th1 and Th17 cytokine profiles were obtained by qPCR, and severity of EAU (on day 21 p.i.) was evaluated by histological grading.
Results: :
In the B10.RIII mice there was significant (P<0.05) reduction in inflammatory cell infiltration in eyes of A-treated animals; photoreceptors were well preserved in these eyes (P<0.05) compared to other three subgroups. The day 7 p.i. retina of A KO mice treated with A compared with untreated mice showed significant downregulation (3- to 31-fold) of TLRs 1-9; adaptors MyD88, Irak1, CD14, Tirap; and NFkB-related genes, including Ccl2, IFN-γ , NFkB, TNF-, and TNF- receptors. On day 21 p.i., compared to retinas of untreated mice, there was significant downregulation of TNF-, IL-12, IFN-γ and IL-17 in the retinas of A-treated KO mice. Moreover, these eyes were free of inflammatory cell infiltration and retinas were well preserved. Ocular changes in wild type mice with EAU were similar to those of KO mice treated with A crystallins.
Conclusions: :
In EAU, A crystallins downregulate both innate and adaptive immune responses in the retina. Moreover, this protein suppresses the inflammatory cell infiltration and prevents retinal damage in EAU.
Keywords: uveitis-clinical/animal model • photoreceptors • crystallins