THE HNK-1 EPITOPE AND THE ELASTIC FIBER SYSTEM OF THE HUMAN CILIARY BODY - AN IMMUNOELECTRON MICROSCOPIC STUDY

Purpose. To localize at the electron microscopic level the cell adhesi on-related HNK-1 carbohydrate epitope in the inner connective tissue l ayer (ICTL) of the human ciliary body. Methods. Seven specimens repres enting the pars plicata (age range, 12 to 86 years) and three specimen s representing the pars plana (age range, 29 to 71 years) of the cilia ry body were sampled at death from eight normal human eyes. Three addi tional specimens from the pars plicata were taken from three eyes with exfoliation syndrome (age range, 78 to 81 years). All specimens were embedded in LR white resin and studied by postembedding immunogold lab elling using two monoclonal antibodies (mAbs) HNK-1 and NC-1 in detect ing the HNK-1 epitope. Results. In the ICTL of the pars plicata and th e pars plana, mAbs HNK-1 and NC-1 constantly hound to the surface of f ibroblast-like cells present in the subepithelial connective tissue ma trix. The immunoreaction was localized along the cell membrane, both a round the cell body and around its long, slender cytoplasmic processes , Long microfibrillar bundles, which consisted of similar to 10-nm thi ck microfibrils in close association with these subepithelial matrix c ells and elastic fibers, were also labelled. The periphery of elastic fibers was likewise immunolabeled for the HNK-1 epitope. The reaction pattern was essentially the same, regardless of age and presence or ab sence of exfoliation syndrome. Conclusions. At the ultrastructural lev el, the HNK-1 epitope in the ICTL is a common denominator to the subep ithelial matrix cells, microfibrillar bundles, and elastic fibers. Thi s suggests that the subepithelial matrix cells secrete this epitope, a nd that molecules bearing it may be involved in joining these connecti ve tissue elements that structurally stabilize the ciliary body.