Immunochemical analysis of tissue antigens in different corneal layers and sclera

Characterization of soluble protein BCP 11/24 from bovine corneal epithelium, different from the principal soluble protein BCP 54

The water-soluble fraction of bovine corneal epithelium was analysed by polyacrylamide gel electrophoresis in the presence of SDS (SDS-PAGE). Next to the principal soluble protein BCP 54, which has recently been identified as a corneal aldehyde dehydrogenase (ALDH), another abundant protein was observed, which we have denoted BCP 11/24, due to its estimated molecular weight of 11 kDa in SDS-PAGE and 24 kDa in high performance gel filtration under non-denaturing conditions. This protein was isolated and characterized by biochemical and immunochemical techniques. The isolation of BCP 11/24 was initially hampered by its tendency to bind non-covalently to BCP 54. BCP 11/24 behaves identically in reduced and unreduced SDS-PAGE and is probably not a glycoprotein. Isoelectric focusing indicated microheterogeneity of BCP 11/24, yielding bands with isoelectric points of 6.1, 5.9, 5.7 and 5.6. A rabbit antiserum directed against BCP 11/24, that did not recognize BCP 54, demonstrated that the distribution of BCP 11/24 in different ocular tissues as well as its light microscopic localization in corneal epithelium is strikingly similar to that of BCP 54. Together with its tendency to interact with BCP 54 in vitro, this suggests the possibility that BCP 11/24 is associated with BCP 54 in vivo, fulfilling a function which may be related to the activity of BCP 54 as a corneal ALDH. In contrast with BCP 54, however, BCP 11/24 was not detectable in corneal endothelium. The antiserum did not detect any immunologically related molecules in corneal epithelium extracts of sheep, human or rat origin, indicating that BCP 11/24 is probably not as highly conserved as BCP 54.

High incidence of corneal epithelium antibodies in Fuch's heterochromic cyclitis

Sera obtained from 26 patients with Fuchs' heterochromic cyclitis were examined for the presence of autoantibodies directed against the anterior segment of the eye by means of immunofluorescence techniques. Antibodies against human iris tissue could not be detected, whereas autoantibodies against corneal epithelium were found in almost 90% of cases. This is the first report describing the presence of autoantibodies in patients with Fuchs' heterochromic cyclitis and it provides a further clue that immunological mechanisms might play an important role in the aetiology of Fuchs' heterochromic cyclitis.

Hybridoma antibodies to insoluble antigens of the corneal epithelium

Human corneal epithelial water insoluble proteins were used to immunize mice. Immune splenocytes were fused with Sp 2/0-Ag14 mouse myeloma cells by 40% PEG. Hybridoma antibodies obtained by somatic cell fusion were tested by radioimmunoassay. Supernatants from antibody positive hybrid colonies were used in immunofluorescence and crossreaction assays to locate and characterize corneal epithelial antigens. At least three distinct epithelial cell antigens were detected, one of which cross-reacts with rabbit corneal epithelial cells.

Immunologic tolerance to collagen and glycosaminoglycan components of scleral allografts in humans. Evidence for T cell suppression

Unfractionated peripheral blood lymphocytes (PBL) and the T and B cell fractions of PBL from four patients who had received scleral allografts, and fractions from four control subjects were tested in vitro for proliferative responsiveness to collagen and glycosaminoglycan-enriched extracts of allogeneic sclera. None of the unfractionated lymphocyte cultures (patients and controls) were responsive to the scleral extracts. However, B-enriched lymphocyte cultures from one patient and two control subjects did respond to the scleral extracts, although there was considerable individual variation in the magnitudes of these responses (stimulation indices ranging from 1.5 to 11.5). In contrast, the DNA-synthesis response of T cells to scleral extracts was strongly suppressed. Furthermore, T cells pre-exposed for 24 hours to scleral collagen were capable of suppressing B-cell responsiveness to mitogens in autologous mixed lymphocyte cultures. Our findings confirm the lack of apparent adverse immunologic responsiveness to scleral allografts in humans as reported by others. It is possible that immunological tolerance to the scleral allografts is due to a suppressor T-cell mechanism which is triggered by scleral collagen.

Inflammatory Terrien's marginal corneal disease

We studied 13 patients with Terrien's marginal degeneration of the cornea. Six of these 13 patients had recurrent, disabling, episodic inflammation that was the most dominant feature of the disease. Severe pain and an associated episcleritis or superficial scleritis was present in all the patients during these attacks. These findings suggested that an inflammatory spectrum of Terrien's disease may exist.

Clinical and laboratory studies on human sclera allografts

In the first section of this two-part report human peripheral blood leukocytes were tested for reactivity to extracts of sclera. Absence of scleral antigenicity is suggested by the results which showed that the leukocytes reacted similarly in sclera stimulated cultures and in the controls. The second part of the report discusses the clinical aspects of sclera allografts and provides guidelines for their clinical use. A case is presented where a sclera graft was in position for approximately a year. The tooth was removed with the attached graft and a histologic study made.

Oral scleral heterografts. A pilot study

This study showed that scleral heterografts in the oral cavity work. Such grafts demonstrate the following characteristics: (1) attach firmly to submucosal, periosteal, and bony tissues; (2) remain firm and fibrotic in nature, indicating the possibility of a stressbearing tissue; (3) show little or no scarring or contracture; (4) show minimal, or no- host antigenic response based on clinical acceptance; (5) appear to become vascularized and cellular, blending with adjacent collagen. As projected by this study, scleral heterografts might well be used to obliterate bony undercuts and perhaps to obtund cystic cavities and other major bony defects. Further studies of layering of the sclera are essential before any definitive result can be determined in large bony defects. In those areas in which no bone regeneration would be feasible, such as in the mylohyoid region of the mandible, this application does present a possibility for removing undercuts as opposed to removing overlying bone. The tenacity of adherence to submucosal tissues, periosteum, and bone makes scleral heterografting even more intriguing in the possible obliteration of oroantral fistulas. We might theorize that the sclera would not only attach to the buccal and palatal flaps but also show a rather firm and tenacious adherence to the bony walls of the antral defect. The availability of human bank sclera for use as presently made by periodontists and as pioneered by Klingsberg is somewhat limited. From our study, an extrapolation would indicate that, because of the comparably low and antigenicity of bovine sclera and human sclera, an investigation in this area should be completed in order to determine whether scleral heterografts can replace scleral homografts in human periodontal surgery. Sclera is easily preserved in anhydrous glycerine (as preserved by King and associates19) and can certainly be stored in banks. In our opinion, the final application of scleral heterografts, human or bovine, the role of antigenicity, and the ability of osteoblasts to invade either a single piece or layers of sclera warrant further study.