Aimlbackground-Endotoxin induced uveitis has been regarded as a model for acute anterior uveitis and until now little was known about choroidal involvement. The aim of this study was to investigate changes in macrophages and MHC class II positive cells in the choroid of Lewis rats during endotoxin induced uveitis. Methods-Choroid-sclera wholemounts were isolated from normal Lewis rats and at different time points-4, 8, 16, 24, 48, 72, and 96 hours, and 7, 10, and 14 days after a footpad injection of 200 μg of lipopolysac-charide (LPS). Immunohistochemistry was performed using the monoclonal antibodies EDI (monocytes, macro phages, dendritic cells), and OX6 (MHC class II antigen).Results-In normal rats, two layers of macrophages were identified in the choroid; a layer located immediately beneath the retinal pigment epithelium (RPE) and a layer bordering the sclera.The density of EDI positive cells in the layer bordering the RPE cells was 902 (SD 132) cells/mm2 whereas the sclerai layer had a cell density of 389 (73) cellslmm:2.Based on morphology, positive cells could be divided into two main categories; pleomorphiclround cells and dendrite form cells with varying appearances, with the latter being predominant in normal eyes. A network of MHC class II positive dendritic cells was found in the choroid, beneath the RPE, with a density of 659 (96) cells/ram2. No MHC class II positive cells were found in the macrophage layer bordering the sclera. LPS injection caused a massive influx of ED1 positive macro phages in the area below the RPE cells but did not result in an influx of macrophages at the scleral side of the choroid. The infiltrate reached a maximum at 16 hours following LPS injection and decreased at 96 hours. The morphology of the infiltrating cells was pleomorphic/round at early stages of inflammation and changed into a dendritlform cell population later. The number of MHC class II positive cells on the anterior side of the choroid increased 8 hours after injection and reached a peak at 72-96 hours. MHC class II positive cellswere not observed in the vicinity of the sclera at any time after LPS injection. Both resident and MHC class II positive dendritic cell numbers returned to norreal values at day 14 following LPS injection. Conclusions-These results indicate that the choroid is severely inflamed after systemic LPS administration to Lewis rats and suggests that endotoxin induced uveitis may serve as a model for generalized uveitis in humans.

Purpose. To investigate the density, distribution, and morphology of macrophages (bone marrow-derived microglia) and major histocompatibility complex (MHC) class II-positive cells in the retina of Lewis rats and the dynamics of these cells after systemic lipopolysaccharide (LPS) injection. Methods. Immunohistochemistry was carried out using monoclonal antibodies specific to monocytes and macrophages (ED1, ED2) and MHC class II-positive cells (OX-6) on whole-mounts of the retina obtained from Lewis rats before and at different time points after footpad injection of 200 g of LPS. Results. The inner layers of the normal retina contained a network of macrophages, whereby ED1 and ED2 staining revealed similar results. Macrophages were either dendritiform or pleiomorphic in morphology, with the former predominant. The density of positive cells was higher at the peripheral part and the periequatorial part (271

Retinal microglia originate flom hemopoietic cells and invade the retina from the retinal margin and the optic disc, most likely via the blood vessels of the ciliary body and iris, and the retinal vasculature. respectively. The microglial precursors that appear in the retina 34-325oJerent microglia popula.prior to vascularization arc major histocompatibilily complex (MHC) class 1-and II-positive and express the CD45 marker, but lack specific macrophage markers. They differentiate into ramified parenchymal microglia in the adult retina. A second category of microglial precursors, which do express specific macrophage markers, migrate into the retina along with vascular precursors. They appear around blood vessels in the adult retina and are similar to macrophages or cells of the mononuclear phagocyte series (MPS). Microglia are distributed in the outer plexiform laver (OPL), outer nuclear laver (ONL), inner plexiform layer (IPL), ganglion cell layer (GCL), and nerve fiber laver (NFL) of the primate retina. The pattern of microglial distribution in the avascular retina of the quail indicates that blood vessels are not responsible for the final location of microglia in the retina. In the human retina, microglia express MHC class l, MHC class II, CD45. CD68, and $22 markers. In the rat and mouse retina. OX41, OX42, OX3, OX6. OX18, ED1, Mac-l, F4/80, 5D4 anti-keralan sulfate, and lectins are used to recognize microglia. Microglial cells play an important role in host defense against invading microorganisms, immunoregulation, and tissue repair. During neurodegeneration, activated microglial cells participate in the phagocytosis ol debris and facilitate regenerative processes. In autoimnmne disease, microglia have dual functions: initialing uveoretinitis, but also limifing subsequent inflame marion. Retinal microglia may he associated wiih vitreoretinopathy, diabetic retinopathy, glaucoma, and age-related macular degeneration. The goal of this article was to review the present knowledge about retinal microglia and the function of retinal microglia in pathological conditions.

Purpose: Recent studies have shown that experimental uveitis can be induced by the appropriate administration of various retinal antigens. Little is known about the in-situ interactions between immune cells in the retina as a prerequisite for understanding the mechanisms involving the presentation of antigens by local antigen-presenting cells (APC) to invading T cells. The study described here was therefore designed to investigate the presence of immunocompetent cells with a focus on the characterization of retinal APCs. Materials and methods: Retinal whole mounts, cytospins, and ocular sections were prepared from eyebank eyes obtained within 24 hours postmortem. Immunohistochemistry (single staining and double staining) was performed on the retinal wholemounts, cytospins, and the ocular sections using monoclonal antibodies specific for HLA-DR (MHC class II), CD45 (leukocytes), CD68 (macrophages), CD2z (B cells), CD3 (T cells), and CDLa (dendritic cells). Results: CD68 positive macrophages were observed in one layer of the retina, whereas HLA-DR~ and CD45+ cells were seen in two distinct planes: one mainly at the level of the inner nuclear layer to outer plexiform layer (deep layer) and the other mainly at the nerve fiber and ganglion cell layer (shallow layer). There was a significant difference between the different parts of the retina with regard to the density of these cells. Cell density decreased when going from the peripheral to the posterior areas of the retina. The positive cells in the deep layer were frequently associated with blood vessels, whereas the cells in the shallow layer were distributed evenly throughout the retina. Most positive cells displayed a dendritiform appearance, whereas few cells showed a pleiomorphic morphology. Very few CDIa-positive cells were noted in the retina. Neither T cells (CD3) nor B cells (CD22) could be detected in the normal human retina. Double staining showed that the majority (83.7%) of the CD45~ cell population Was I-ILA-DR-positive, whereas approximately half (56.8%) the CD68~Cell population was HLA-DR-positive. Conclusions: This study shows that the human retina contains a number of different microglia populations, some of which express HLA-DR and could thus be involved in antigen presentation. Marked differences in cell density can be observed within the retina, with the most abundant presence seen in the peripheral retina. The normal retina contains few professional antigen-presenting cells (CDI+).

Aims: To evaluate the expression of Fas/FasL antigen on peripheral blood T lymphocytes in patients with Behcet's disease, VogtKoyanagi-Harada (VKH) syndrome, and idiopathic anterior uveitis. Methods: The expression of Fas and FasL on peripheral blood T lymphocytes was determined using flow cytometry in 26 patients with Behcet's disease (BD), 17 patients with VKH syndrome, 25 patients with idiopathic anterior uveitis, and 43 healthy individuals (controls). Results: A higher proportion of CD4+T cells expressing Fas was noted in patients with Behcet's disease (25.70