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 adhesion molecule epitope in the lens-ciliary zonular region in normal and pseudoexfoliative (PSX) eyes.

METHODS

Normal and PSX eyes and adjacent tissues from individuals aged 10 months to 89 years were investigated for the HNK-1 epitope by immunohistochemistry and immunogold electron 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 and on normal elastic microfibrils in these tissues.

CONCLUSIONS

The prominent HNK-1 epitope in lens capsule and zonule has age- and site-specific variations that favor adhesive roles in each. The high density of epitope on ocular PSX material suggests an aberrant increase in expression that may contribute to adhesiveness of these aggregates, HNK-1 negativity on extraocular elastic microfibrils and PSX aggregates indicates a unique difference in composition of intraocular and extraocular elastic tissue, of potential significance for ocular function in aging and lens-dislocating diseases.