Electron Microscopy of Experimental Uveitis

¹ Department of Ophthalmology, Columbia University, New York, N.Y.; Fight for Sight Research Fellowship No. F-193 of the National Council to Combat Blindness Inc., New York, N. Y.
² Department of Ophthalmology, Columbia University, New York, N.Y.

The fine structural features of the early pathological changes induced in uveal tissue by single intravitreal injections of three different quantities of bovine serum albumin (BSA) in rabbits xoere studied. Small quantities of antigen (BSA) did not produce clinical signs of uveitis but a mild leukocytic infiltration (mainly monocytes) was found in the base of the ciliary body. The occasional basophilic leukocytes in the reaction site and choroidal mast cells xoere not degramdated and no alteration in the blood-aqueous barrier was found. Larger quantities of BSA produced mild uveitis and an impressive mononuclear infiltration in the base of the ciliary body, the root of the iris, the pars plana, and the peripheral choroid. The infiltrating cells included some xohich appeared to be intermediate between small lymphocytes and plasma cells, as well as monocytes. Intercytoplasmic connections between monocytes and lymphocytes were observed, suggesting that immunological information was transferred by this means. Emigration of all types of mononuclear cells from blood vessels, and their passage through the ciliary epithelium into the posterior chamber, was frequently noted; however, in these regions, little alteration was observed in the structures associated with the blood-aqueous barrier. Small lymphocytes passed through, and larger mononuclear cells between, the endothelial cells ivhen leaving the vascular system. Small islands of polymorphonuclear (PMN) heterophilic leukocytes were also seen in both the iridial and ciliary processes. In these regions, pronounced alteration tuas found in the blood-aqueous barrier and both basophilic leukocytes and mast cells showed degranidation. Injection of a still larger amount of BSA provoked severe uveilis with massive PMN heterophilic infiltration in the base of the ciliary body and in localized areas in the iridial and ciliary processes. Significant hemorrhage, thromboses, and necrosis of blood vessels were observed in the ciliary body. The structures associated with the bloodaqueous barrier shoxved marked changes. In addition to such vascular alterations, mononuclear cell infiltration ivas seen in the pars plana and. the peripheral choroid.

Key Words: allergic uveitis • albumin • intravitreal injection • epithelium of ciliary processes • blood-aqueous barrier • antigen-antibody reaction • histopathology • electron microscopy