Re-programming immunosurveillance in persistent non-infectious ocular inflammation

Abstract

Ocular function depends on a high level of anatomical integrity. This is threatened by inflammation, which alters the local tissue over short and long time-scales. Uveitis due to autoimmune disease, especially when it involves the retina, leads to persistent changes in how the eye interacts with the immune system. The normal pattern of immune surveillance, which for immune privileged tissues is limited, is re-programmed. Many cell types, that are not usually present in the eye, become detectable. There are changes in the tissue homeostasis and integrity. In both human disease and mouse models, in the most extreme cases, immunopathological findings consistent with development of ectopic lymphoid-like structures and disrupted angiogenesis accompany severely impaired eye function. Understanding how the ocular environment is shaped by persistent inflammation is crucial to developing novel approaches to treatment.

Keywords: Angiogenesis; EAU; Ectopic lymphoid tissue; Immunosurveillance; Uveitis.

Fig. 1

Ocular infiltration by lymphocytes is comprised of a diverse population of cells. (A) The prodrome is characterised by an initial slow localisation of cells to the eye, followed by rapid accumulation and secondary regulation. (B) Lymphocytes were prepared from the vitreous, retina and ciliary tissue of C57BL/6 animals with acute EAU (day 23–25) and persistent disease (day 38–43). Populations of live CD45 positive, CD11b negative cells were quantified by multiparameter flow cytometry. Adapted from Kerr et al., 2008a, Kerr et al., 2008b Prog. Retin. Eye Res. 27, 527–535 & Boldison et al. (2014). J Immunol 192, 4541–4550.

Fig. 2

Lymphocyte populations in human uveitis. Lesions stained with different markers of leukocyte phenotype are shown. (A) Immunohistochemistry of the choroid of a 29 year old woman with persistent non-infectious uveitis (Idiopathic uveitis) demonstrating different lymphocyte populations. (B) Serial section of a single lesion showing follicle like structure in human uveitis. Immunohistochemistry images of the choroid of a 28 year old woman with persistent non-infectious uveitis (scleritis, episcleritis and uveitis) demonstrating features of ectopic lymphoid-like structures: T cells surrounding B cells and evidence of active recombination (BCL6+ and AID + cells.) In both cases enucleation was carried out a for blind painful eye, late in the disease process. Photomicrographs show T cells (CD3⁺, CD4⁺ and CD8⁺), B cells (CD20⁺), Follicular B cells(CD23⁺), Plasma cells (CD138), Follicular Dendritic Cells (CD21⁺) and macrophage/monocytes (CD68⁺). Granulomas were not identified in these specimens. All images ×400 magnification.

Fig. 3

Animals (C57BL/6) were immunized with IRBP 1–20 to induce EAU and clinical disease was monitored by topical endoscopic fundal imaging (TEFI), fluorescein angiography and optical coherence tomography. At day 146 persistent disease neovascular membranes (white arrows), extending into the retina and fused with the RPE are seen (A–C). The neovascular membranes in wild type animals are associated with CD11b positive macrophages (D–F) and disruption of collagen IV. Gene manipulations that target macrophage function can modify the vascular phenotype, for example when C57BL/6 wild type (G) and C57BL/6 TNFR1 (H) knockout animals with persistent EAU were assessed 90 days after the induction of EAU by preparing retinal flatmounts and staining with collagen IV, confocal microscopy showed more vascular modifications in the wild type animals. Photography, angiography and OCT were carried out using TEFI and a micron IV retinal imaging microscope (Phoenix research laboratories). Collagen IV stain used a primary rabbit anti-mouse antibody and secondary staining with goat anti-rabbit conjugated with AlexaFluor 568 (red E,F) or AlexaFluor 488 (green G,H). Scale bar panel C 100 microns.