Immunofluorescent detection of Histoplasma capsulatum in primate experimental ocular histoplasmosis.

We have developed a polyclonal anti-Histoplasma capsulatum antibody to detect H. capsulatum antigens in ocular tissue. Antibodies were specific for H. capsulatum as determined by enzyme linked immunosorbent assay and immunoprecipitation. A total of 21 choroidal histoplasmic lesions in 4 primate eyes (Macaca speciosa and Macaca mulatta), taken at various times from 14 to 60 days after the internal carotid artery injection of yeast phase organisms, were evaluated. Using an indirect immunofluorescent technique, these antibodies stained yeast phase organisms within acute choroidal lesions at 14 days after infection. By 60 days intact organisms were no longer detected; occasional cells, however, contained intracellular inclusions that stained with these antibodies. Although yeast phase organisms are rapidly cleared from the primate choroid, these data indicate that residual H. capsulatum antigens may remain in choroidal lesions after the acute infectious stage. These findings are consistent with the hypothesis that H. capsulatum antigens play a role in the immunologic reactivation of atrophic choroidal scars in ocular histoplasmosis.

The selective suppression of immunogenicity by hyaluronic acid.

A hyaluronidase-sensitive component of human peritoneal fluid from a patient with Wilms' tumor when injected into rabbits has been shown to suppress the formation of humoral precipitating antibodies to certain major classes of proteins present in the fluid. Furthermore, it has been found that hyaluronic acid, when included with certain test antigens (serum albumin, fetuin) or antigen mixtures (tumor isolates or mixtures of albumin, immunoglobulin G and immunoglobulin M), produces a marked distortion or complete blockage of immunoelectrophoresis precipitin arcs, as well as altered gel chromatography elution profiles. These findings that hyaluronic acid can interfere profoundly with both the elicitation of a complete antibody response and the formation of "normal" patterns of antigen-antibody precipitates in laboratory tests supports the possibility that this polysaccharide may play an immuno-regulatory role by masking potential immunogens. Consideration of the mechanisms for these in vivo and in vitro effects suggests that there may be some common basis in an "excluded volume" property of the hyaluronate, but this does not appear sufficient to explain the complexity and selectivity of the observed phenomena.

Modulation of lens-induced uveitis by superoxide dismutase.

Recent studies on reactive oxygen metabolites have suggested that these products may be important mediators in the early tissue damage that develops from immunopathologic inflammations. The superoxide anion appears to be the principal product of the respiratory burst. In order to determine the effects of removing superoxide with superoxide dismutase on modulating the inflammation in experimental phacoanaphylactic endophthalmitis, the animals with this experimental disorder were treated with superoxide dismutase. The treatment resulted in significant reduction of choroidal inflammation, retinal edema and vasculitis, suggesting phlogogenic role of superoxide in the ocular immune-complex disease.

Superoxide dismutase in ocular structures.

Specific immunohistochemical localization of superoxide dismutase in ocular tissue of Lewis rats revealed the presence of this enzyme predominantly in the corneal epithelium, endothelium, apical regions of the posterior epithelium of the iris, nonpigmented inner ciliary epithelium, lens epithelium, inner segments of photoreceptor cell layer of the retina, and retinal pigment epithelium. This enzyme is distributed primarily in those ocular structures which may be frequently exposed to superoxide or its metabolites under physiologic conditions and in such pathologic processes as intraocular inflammations. It thus appears that superoxide dismutase and other antioxidants may play a protective role in preventing the damaging effects of oxygen radicals.

Adherence of Candida to corneal surface.

In the pathogenesis of mycotic infections, adherence of the microbes to surface structures prior to invasion appears to be the initial and essential step in a susceptible host. Adherence and inhibition of adherence of Candida albicans to rabbit corneal surface was investigated in vitro by light and scanning electron microscopic examinations. The results indicate that blastospores of Candida albicans rarely bind to intact corneal epithelium, but consistently adhere to stroma denuded of epithelium. Such adherence was inhibited by concanavalin A. With its strong affinity for the yeast cell wall carbohydrate mannan, concanavalin A may block the site of attachment of yeast cells to the corneal surface.

Intraocular injection of silicone oil for experimental proliferative vitreoretinopathy.

We evaluated the effect of intraocular silicone oil as an internal tamponade on an animal model of proliferative vitreoretinopathy. Lensectomy and vitrectomy were performed on two groups of pigmented rabbits. Twenty-five rabbit eyes then had 1,000 centistokes' viscosity silicone oil injected into the vitreous cavity; 20 control eyes received balanced salt solution. Fourteen days later, each eye was injected with homologous fibroblasts (ten eyes with 100,000 cells, 25 eyes with 250,000 cells, and ten eyes with 750,000 cells). All membranes that developed after the cell injections in both experimental and control eyes produced traction retinal detachment. The character of the membranes formed and the timing of the traction retinal detachment were the same for both groups. In an active phase of experimental proliferation, the internal tamponade of silicone oil is insufficient to keep the retina in place.