Intraokulare Entzündungen. Pathologie des Auges. Berlin: Springer Berlin Heidelberg; 1980. pp. 88-175. [DOI: 10.1007/978-3-642-96500-5_4]

Immunohistochemical studies in equine recurrent uveitis (ERU)

Despite extensive clinical research, the etiology of equine recurrent uveitis (ERU) is still unknown. After an immunologic pathogenesis was established in recurrent uveitis in humans, a similar pathogenic mechanism was assumed to exist in ERU. To investigate whether immunopathologic mechanisms are involved in ERU, 20 eyes of 15 horses with ERU were examined immunohistochemically with a T cell marker, B cell marker, and anti-major histocompatibility complex (MHC) class II antibodies. Twenty-six eyes of 20 horses were used for investigation of MHC class II antigen expression in normal equine eyes. In 18 eyes of 14 horses, the number of T cells in the inflammatory cell population within the uvea was assessed. In 16/18 eyes (89%), the T lymphocyte fraction was > 70%. This cell population was distributed mostly in a diffuse manner throughout the uvea and also within the mantle zone of follicular lymphocytic aggregates. Foci of B lymphocytes could be found within the center of follicular aggregates in three eyes. The expression of MHC class II antigen on resident ocular cells was evaluated in 10 eyes of six horses with ERU. An increase of MHC class II antigen expression in the trabecular meshwork and on the nonpigmented ciliary epithelium was noted as was a deviant expression on proliferating Müller cells and retinal pigment epithelial cells. The predominance of T cells in the inflammatory infiltrates supports the central role of a cell-mediated immune response. Furthermore, the observation of a deviant MHC class II expression on resident ocular cells suggests that aberrant immune regulation may play a role in the pathogenesis of ERU.

Bone-marrow transplantation and toxoplasmic retinochoroiditis

A 33-year-old woman underwent bone-marrow transplantation following radiation and chemotherapy for chronic myelocytic leukemia (CML); immunosuppressive therapy was continued for graft-versus-host disease. Five months after successful transplantation, she developed necrotizing retinitis in both eyes with rapid progression over the following weeks. Due to her immunosuppressed state the patient developed pneumonia and died. Postmortem evaluation of the retinal lesions in both eyes disclosed infection by Toxoplasma gondii, which was also found in the brain and myocardium. Multiple viable toxoplasmic cysts were observed at the transition zone from a necrotic to a normal retina. Additionally, cysts of Toxoplasma gondii a normal retina. Additionally, cysts of Toxoplasma gondii were seen in the adjacent intact retina and in areas of necrosis with almost complete absence of retinal or choroidal inflammation. Toxoplasmosis should therefore be considered along with fungi and viruses in the differential diagnosis of necrotizing retinochoroiditis in immunocompromised patients.