Experimental autoimmune uveoretinitis. Ultrastructure of chorioretinal lesions induced in guinea pigs by immunization against the outer rods of the bovine retina.

The uveoretinitis induced in guinea pigs by one systemic injection of rod outer segments from bovine retina has the following ultrastructural features : 1 to 3 weeks after the injection, first early alterations of the visual cells and pigment epithelium, phagocytosis of fragmented outer segments by macrophages, development of an inflammatory infiltrate of the uvea with numerous plasma cells. During the second month, polymorphic inflammatory reaction in the choroid, destruction of photoreceptors in large areas with preservation of the external limiting membrane or involvement of the internal layers of the retina. During the next months, fibroblastic healing processes, but persistence of a diffuse inflammation, with sub-retinal lymphoid follicles and epithelioid cells. It appears likely that pigment epithelium and outer segments of the visual cells are targets for the initial immunological attack, where humoral antibodies seem to play a major role.