HNK-1 EPITOPE IN THE LENS-CILIARY ZONULAR REGION IN NORMAL AND PSEUDOEXFOLIATIVE EYES - IMMUNOHISTOCHEMISTRY AND ULTRASTRUCTURE

Objective: To determine the specific binding sites for the HNK-1 adhes ion molecule epitope in the lens-ciliary zonular region in normal and pseudoexfoliative (PSX) eyes. Methods: Normal and PSX eyes and adjacen t tissues from individuals aged 10 months to 89 years were investigate d for the HNK-1 epitope by immunohistochemistry and immunogold electro n microscopy. Results: Concentration of HNK-1 epitope was high in the anterior central lens capsule into old age, but it tapered earlier and progressively in the inner capsule and elsewhere. On zonular fibers, label was strongest at their lens and ciliary attachments and intense on related elastic microfibrils in adjacent ciliary stroma. Label was also strong on PSX fibers and above normal on PSX central capsule. In contrast, HNK-1 was absent on PSX aggregates in conjunctiva and skin a nd on normal elastic microfibrils in these tissues. Conclusions: The p rominent HNK-1 epitope in lens capsule and zonule has age- and site-sp ecific variations that favor adhesive roles in each. The high density of epitope on ocular PSX material suggests an aberrant increase in exp ression that may contribute to adhesiveness of these aggregates. HNK-1 negativity on extraocular elastic microfibrils and PSX aggregates ind icates a unique difference in composition of intraocular and extraocul ar elastic tissue, of potential significance for ocular function in ag ing and lens-dislocating diseases.