shares many similarities with the human eye and is considered as a suitable species to investigate the pathogenesis of human ocular disease. The aim of this study was to investigate the presence of immunocompetent cells in the uveal tract of the normal pig. Methods. Iris and choroid wholemounts and cryostat sections were obtained from normal pig eyes. Single and double immunohistochemistry was performed by using anti-porcine leukocyte (CD45), anti-porcine macrophage (CD163, CD14), anti-porcine MHC class II (MCA1335), anti-human MHC class II (MCA379G), anti-porcine B lymphocyte (IgM), anti-porcine T lymphocyte (CD6) and anti-porcine granulocyte (MCA1219) monoclonal antibodies. Results. A rich network of dendritiform CD163 positive tissue macrophages was observed in normal pig iris and choroid wholemounts (368+84/mm2, 402+97/mm2, respectively). Approximately 50% of the CD163 positive tissue macrophages in the iris coexpressed MHC class II. Double immunostaining revealed that a small population of the MHC class II positive cells, did not express macrophage markers, and probably represent classical DCs. B lymphocytes and granulocytes were not detected in iris and choroid whole mounts. An occasional T cell could be observed per high power field in iris wholemounts but not in the choroid. Conclusions. The present study reveals that the normal piguveal tract contains a rich network of tissue macrophages and MHC class II positive dendritiform cells. At least three populations could be distinguished: MHC class II positive and negative tissue macrophages and MHC class II+ dendritiform cells lacking tissue macrophage markers.

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.

ononuclear cells were isolated by centrifugation with Ficoll-Paque and cultured in RPMI 164o with or without phytohemagglutinin (PHA) for 9h at 37℃ in an atmosphere with 5% CO2. The obtained cells were incubated with anti-Fas antibody for 8h at 37℃ in an atmosphere with 5% CO2. The cells were stained with annexin V/propidium iodide and finally subjected to flow cytometry. Results: A significantly lower percentage of apoptotic lymphocytes after PHA stimulation was noted in Behcet's disease (19.7±4.1%) and VKH syn drome (2o.4±6.9%) than in controls (26.1±7.3%). The percentage of apoptotic lymphocytes without PHA stimulation also tended to be lower in the patients with BehCet's disease (12.6%) and with VKH syndrome (12.8%) than in controls (14.6%), although the difference was not significant. Conclusion: Lymphocytes in patients with either Behcet's disease or VKH syndrome are relatively resistant to apoptosis mediated by anti-Fas antibody. These apoptosis-resistant, or longlived, lymphocytes may be involved in the chronic and recurrent intraocular inflammation seen in these patients.

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