The superficial basal lamina of ciliary processes: binding studies with IgG-immunogold and ferritins

In this study, we employed two ultrastructurally visible probing systems, IgG-immunogold and ferritin molecules which differ by surface charge, to study binding activity of the aqueous face of the posterior ciliary processes in short term tissue baths. With these probes we demonstrated that the superficial basal lamina of the non-pigmented epithelium binds monomeric and heat aggregated IgG but not IgG F(ab')2. Binding was inhibited by preincubation with monosaccharides and NaCl suggesting that IgG binding was determined by lectin-like and electrostatic interactions. Anionic binding domains within the basal lamina, capable of exerting an electrostatic influence, were directly demonstrated by selective binding of cationic ferritin species. At high concentrations of cationic ferritin, anionic binding sites were saturated and tracer penetrated the basal lamina to reach intercellular spaces between non-pigmented epithelial cells. We concluded that the superficial basal lamina of the ciliary processes, which is bathed by the aqueous humor, may bind and immobilize IgG, IgG-opsonized antigens and accessible carbohydrate or cations on other molecules in this fluid. This binding may be important in the maintenance of normal aqueous humor composition and in the pathogenesis of infectious and immune-mediated ocular disease.